Article No : a03_213

Azine Dyes
HORST BERNETH, Lanxess Deutschland GmbH, Leverkusen, Germany

1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . 475 3.1. Monoaminophenoxazine Dyes . . . . . . . . . . .492

2. Phenazine Dyes . . . . . . . . . . . . . . . . . . . . . 479 3.2. Diaminophenoxazine Dyes . . . . . . . . . . . . . .493
2.1. Monoaminophenazine Dyes . . . . . . . . . . . . .479 3.3. Aminohydroxyphenoxazine Dyes . . . . . . . . .496
2.2. Diaminophenazine Dyes . . . . . . . . . . . . . . . .480 3.4. Mono- and Dihydroxyphenoxazine Dyes . . .497
2.2.1. Eurhodine Dyes. . . . . . . . . . . . . . . . . . . . . . .480 4. Thiazine Dyes . . . . . . . . . . . . . . . . . . . . . . 497
2.2.2. Basic Safranine Dyes. . . . . . . . . . . . . . . . . . .481 4.1. Diaminophenothiazine Dyes. . . . . . . . . . . . .498
2.2.3. Acid Safranine Dyes . . . . . . . . . . . . . . . . . . .482 4.2. Aminohydroxyphenothiazine Dyes. . . . . . . .500
2.2.4. Indulines . . . . . . . . . . . . . . . . . . . . . . . . . . . .484 4.3. Hydroxyphenothiazine Dyes . . . . . . . . . . . .501
2.2.5. Nigrosines. . . . . . . . . . . . . . . . . . . . . . . . . . .485 5. Bisazine Dyes . . . . . . . . . . . . . . . . . . . . . . . 501
2.2.6. Aniline Black . . . . . . . . . . . . . . . . . . . . . . . .487 5.1. Fluorindine Dyes . . . . . . . . . . . . . . . . . . . . .502
2.2.7. Oxidation Dyes . . . . . . . . . . . . . . . . . . . . . . .489 5.2. Dioxazine Dyes. . . . . . . . . . . . . . . . . . . . . . .502
2.3. Aminohydroxy- and Monohydroxyphenazine 5.3. Dithiazine Dyes . . . . . . . . . . . . . . . . . . . . . .507
Dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .491 References . . . . . . . . . . . . . . . . . . . . . . . . . .507
3. Oxazine Dyes . . . . . . . . . . . . . . . . . . . . . . . 491

1. Introduction In these formulas D1 and D2 stand for an

auxochrome group, usually an amino, arylamino,
The azine dyes include the phenazine, the ox- monoalkylamino, dialkylamino, or hydroxy
azine, and the thiazine dyes. They correspond to group; X stands for

O

,

S

, or

NR


the following general formula, the most impor- (R ¼ H, alkyl, aryl); and n is 0 or 1. Therefore,
tant resonance formulas of which are shown: resonance f3ormula 1c only has meaning when
n ¼ 1. The azine dyes include cationic, anionic,
and neutral dyes, depending on the kinds of
auxochrome groups and substituents. The multi-
tude of possible resonance formulas is responsi-
ble for the deep and intense color of the azine
dyes. The azine dyes have this in common with
the methine dyes and the triphenylmethane dyes,
and they all obey the same general theory of
methine dyes [1].
Monoamino- and diamino-, monohydroxy-
and dihydroxy-, and aminohydroxyazine dyes
are differentiated according to the kind and num-
ber of auxochrome groups in formulas 1a – 1c.
Because hydroxyazine dyes are present predom-
inantly in the keto form (D1 or D2 is ¼O), they are
referred to as phenazone, phenoxazone, and
phenothiazone dyes.

2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI: 10.1002/14356007.a03_213.pub3
476 Azine Dyes Vol. 4

It is clear from the general formulas above

that, because of the

X

moiety, azine dyes are
cyclized derivatives of indamine or indophenol
dyes. This relationship is not only of a formal
nature; the most important methods of prepara-
tion of the phenazine, oxazine, and thiazine dyes
proceed via an intermediate indamine or indo-
phenol dye. Either one component of these inter-
mediates already contains the

XH group, and
ring closure can take place immediately, or the


XH group must first be introduced into the
indamine or indophenol dye in a separate step.
Oxazine dyes are prepared by the former proce-
dure, thiazine dyes by the latter, and phenazine
dyes by both.
LOVELESS, BROWN, and HORROCKS [2] investi-
gated spectrophotometrically the formation of
the phenazine ring via cyclization of N-(2-ami-
nophenyl)-p-benzoquinonediimine 3, the oxida-
tion product of 2,40 -diaminodiphenylamine 2. In
the pH range 6 – 9, the amino group adds intra-
molecularly to the quinone ring, and 2-amino-
phenazine 4 is formed by oxidation. Above
pH 10, hydrolysis of the imino group occurs, In an investigation of the reaction kinetics,
and N-(2-aminophenyl)-p-benzoquinoneimine CORBETT [3] was able to establish the following
5 is formed. In this case, too, the amino group mechanism of formation of phenosafranine 9 by
adds to the quinone ring, and 2-hydroxyphena- the joint oxidation of p-phenylenediamine and
zine 6 is obtained by oxidation. aniline:
Vol. 4 Azine Dyes 477

A rapid oxidation reaction is followed each the aniline moiety yielding 10. Subsequently, an
time by the rate-determining nucleophilic addi- autocatalytic reaction begins according to the
tion of aniline to the quinoid system. The final scheme below:

addition step takes place intramolecularly, form- Common to both reaction mechanisms is the
ing the phenazine ring system. In a similar sys- fact that two indamine intermediates (7 and 8,
tem, the formation of indophenols in the Gibbs and 11 and 12, respectively) precede the forma-
reaction, the initial step is a single electron tion of the phenazine dyes 9 and 13.
transfer reaction between the quinoid system and The ring-forming sulfur atom in the thiazine
the phenolate anion followed by fast combination dyes is also introduced by addition to a quinoid
of the radicals or by a chain reaction sequence [4]. intermediate. In addition to hydrogen sulfide
A further method for preparation of phenazine and sulfides, sodium thiosulfate is used as sulfur
dyes involves the reaction of azo compounds donor in the most important industrial prepara-
with aromatic amines. In this case, the formation tion procedure [6]; thiosulfonic acids are
of the indamine is preceded by a series of oxida- formed as intermediates, which are cyclized via
tion, reduction, and disproportionation reactions the indamine 14 to the thiazine dye 15. This
[5]. The first step is the exchange of the 1-amino reaction sequence was elucidated as early as
group of 1-amino-4-benzeneazonaphthalene for 1885 by BERNTHSEN for Methylene Blue.
478 Azine Dyes Vol. 4

Azine dyes with hydroxy groups as auxo-

chromes are prepared analogously by cyclization
of indophenols 17, which are obtained by the
action of aromatic amines on aromatic hydroxy
compounds:

In dyes that contain only one auxochrome

In the preparation procedures discussed so far, group, i.e., in which n ¼ 0 in the general formula
the indamine dye that is required as intermediate 1, a second auxochrome group D2 can be intro-
is always prepared by oxidation of 1,4-diamines. duced if, instead of this group, a nucleophilically
It can also be obtained by the condensation of replaceable group is present, e.g., the sulfo
nitroso derivatives of aromatic amines in acidic group [9]:
alcoholic solution. The reaction is especially used
for the preparation of oxazine dyes. 3-Hydroxya-
nilines are used as aromatic amines that contain
the ring-closing oxygen atom [7]. When the ni-
troso compound contains an alkoxy group, cycli-
zation can also take place with elimination of
alcohol. This is the case for Basic Pure Blue G 16
[8], which is especially important industrially.
Vol. 4 Azine Dyes 479

In the absence of such a leaving group, the obtained in 1876 by joint oxidation of 1,4-phe-
introduction of the auxochromic group is carried nylenediamine and hydrogen sulfide with iron
out successfully by the use of oxidizing agents. (III) chloride. However, the dye class achieved
Starting from phenazinium salts monoaminophe- industrial importance only when CARO discov-
nazine dyes [10] and even diaminophenazine ered Methylene Blue that same year at BASF.
dyes can be obtained in a similar way [11]: Meldola’s Blue [7057-57-0], the condensa-
tion product of nitrosodimethylaniline and
2-naphthol, was described in 1879; it is the oldest
industrially produced oxazine dye. In 1928,
KR€aNZLEIN, GREUNE, and THIELE discovered the
group of dioxazine dyes by reaction of aromatic
amines with chloranil followed by cyclization,
the triphendioxazine base structure itself being
known since 1890.

2. Phenazine Dyes
Starting from 10H-phenothiazine two (sub-
stituted) anilino groups can be introduced as The basic aminophenazine dyes are suitable for
auxochromes by using iodine as oxidizing dyeing wool, silk, and leather directly, and cotton
agent yielding 3,7-bis(arylamino)phenothiazine mordanted with tannin or Katanol. They are only
dyes [12]. still of importance as leather dyes or for the
dyeing of paper pulp. The basic aminophenazine
History. The oldest synthetic organic dyes dyes also include the nigrosine and the induline
belong to the group of azine dyes. In 1834, RUNGE bases. The former are still widely used today to
found that aniline salt yielded dark green pig- color phenolic resin moldings, typewriter rib-
ments on oxidation with dichromate or other bons, shoe polishes, and printing inks, as well
oxidizing agents. LIGHTFOOD studied the oxida- as for the spin dyeing of polyacrylonitrile fibers.
tion of aniline in the presence of copper salt as The dyes that contain sulfo groups exhaust
oxygen-transfer agent and thus found in 1863 the from neutral or acidic bath onto wool. They level
first industrially useful procedure for the prepa- satisfactorily; some are distinguished by good
ration of Aniline Black [13007-86-8]. fastness to washing and to fulling and by ade-
In 1856, PERKIN discovered mauveine 18 [13], quate fastness to light. The acidic nigrosine and
which imparted to silk violet hues having a induline dyes are suitable for the dyeing of paper
beauty so far unknown; it was also used to print and leather.
postage stamps: The oxidation dyes are also classed with the
phenazine dyes. They are formed when aromatic
mono- and diamines applied to human hair or
animal hairs or to cotton or synthetic fibers are
treated with oxidizing agents.

2.1. Monoaminophenazine Dyes

Dyes that contain a naphthalene ring system are

The discovery of the induline dyes by CARO industrially useful. Rosinduline dyes bear the
and DALE followed in 1863, and the discovery of amino group on the naphtho ring, isorosinduline
the nigrosines by COUPIER in 1867. Both groups of dyes on the benzo ring. Basic isorosinduline dyes,
dyes represent extremely complex structural which are obtained by reaction of the nitroso
mixtures of phenazine dyes. derivatives of tertiary aromatic amines with N-
The first thiazine dye, named after its discov- alkyl- or N-aryl-2-naphthylamines, are suitable
erer, was Lauth’s Violet [581-64-6], which was for the dyeing and printing of textiles containing
480 Azine Dyes Vol. 4

acid groups. The dye 19, obtained by heating 4- 2.2. Diaminophenazine Dyes
nitrosodiphenylamine and N-phenyl-2-naphthyl-
amine in alcoholic hydrochloric acid, dyes The eurhodines and the safranines belong to the
polyacrylonitrile navy blue [14]. It can be used class of diaminophenazine dyes. The eurhodines
as a color base [15] or as a salt [16] for the bear a hydrogen atom or an alkyl group on the
spin dyeing of polymers or mixed polymers of azine nitrogen atom; the safranines bear a phenyl
acrylonitrile. group, which can be further substituted if neces-
sary. If a naphthalene ring system is fused to the
azine ring, the dyes are called benzophenylsa-
franines or, if naphthalene rings are fused to both
sides, dibenzophenylsafranines. Indulines and
nigrosines bear, in addition to the auxochrome
groups, further phenylamino groups.

2.2.1. Eurhodine Dyes

Basic rosindulines are proposed for the batch
dyeing of polyester materials [17]. Neutral Violet (22, R ¼ H), C.I. 50 030
Induline Scarlet 20, C.I. 50 080 [2611-49-6] [167382-91-4], and Neutral Red (22, R ¼ CH3,
(BASF, 1892), is prepared by heating 1-amino- Toluene Red), C.I. 50 040 [553-24-2] (Cassella),
naphthalene in phenol with the azo dye obtained are seldom used these days. They are obtained by
from aniline and N-ethyl-p-toluidine [18]. condensation of 4-nitrosodimethylaniline with
1,3-diaminobenzene or 1,3-diamino-4-methyl-
benzene [20].

Acid rosinduline dyes are prepared by the The formation of aggregates was investigated
action of oleum or chlorosulfonic acid on the for Neutral Red [21]. The dye can be used for the
color bases, e.g., Azocarmin BX, C.I. 50 090. detection of cells with phagocytic activity [22].
Acylated leuco derivatives of monoamino- Dyes that bear b-chloroethyl groups instead of
phenazine dyes are recommended as magenta methyl groups have antitumor activity [23].
developing components in photothermographic By reaction of Neutral Red with epichlorohy-
dry silver materials [10]. drin, the hydrogen atoms of the amino group are
Acetone can be condensed with two equiva- replaced by 2-hydroxy-3-chloropropyl groups.
lents of 2-amino-4-chlorodiphenylamine under This compound dyes wool, polyamide, and cel-
oxidative conditions. Subsequent quaternization lulose, covalent bonds being formed [24]. In
leads to 21, which dyes polyacrylonitrile in a contrast, methyl halides alkylate the azine nitro-
brilliant orange shade [19]: gen atom and yield dyes which have improved
fastness to alkali.
Dyes with additional alkyl-substituted amino
groups in positions 2 and 8 show a significant
bathochromic shift like indulines (see Section
2.2.4), but in contrast thereto exhibit high fluo-
rescence and singlet oxygen quantum yields [25].
Dyes of the Neutral Red type, as well as basic
safranine dyes, are suitable for fast dyeing
of polyolefin materials in red, violet, and blue
tints [26]. They can be used for dyeing human
hair [27].
Vol. 4 Azine Dyes 481

Acylated leuco derivatives of Neutral Red are Rhoduline Violet (Bayer, 1894), or Leather
disclosed for use in electrochromic recording Red Violet HM 24, C.I. 50 250 [23279-70-1]
materials [28]. (Hoechst), is synthesized by reaction of 4-nitro-
sodimethylaniline with 3-amino-4-methyldiphe-
2.2.2. Basic Safranine Dyes nylamine.

Safranine T extra 23, C.I. 50 240 [477-73-6], is

offered for the dyeing of leather. Preparation
starts with the reduction of aminoazotoluene to
give an equimolar mixture of 2-toluidine and 2-
methyl-1,4-phenylenediamine, and is followed
by oxidation in the presence of added aniline to
give the azine dye.
The amino group is diazotizable. By coupling
with aromatic amines, phenols, and N-hetero-
cycles, the safranine azo dyes are formed (Janus
Black G, Janus Green B, Diazine Black K). The
dyes can be used for dyeing polyacrylonitrile
[44] and acid-modified polyester fibers [45]
and as light filters with variable optical density
By the action of nitrite, it is converted to a blue [36].
diazonium salt, which on heating forms the 3,7- Janus Black R 25, C.I. 11 825 [4443-99-6], is
dihydroxy compound [29]. Safranine T can be formed by coupling diazotized diethylphenosa-
used to remove lignin from mechanical wood franine to phenol.
pulp [30]. The dye is disclosed as colored charge-
controlling agent in toners for electrophotogra-
phy [31] and as photosensitizer in solar cells [32].
Safranine dyes are also suitable for use in photo-
electric processes [33]. Furthermore, they can be
used as desensitizers in direct-positive printing-
out emulsions [34], for photopolymerization
using visible light [35], as light filters with vari-
able optical density [36], and as dye components The dye was commercially available as Su-
in soluble complex-forming molecules used in miacryl Black G (Sumitomo) and as Aizen Cath-
affinity-specific separation of nucleic acids [37]. ilon Grey BLH (Hodogaya) for the dyeing of
Safranine dyes act as redox indicators in the polyacrylonitrile fibers.
quantitative analysis of metal ions, e.g., rutheni- By coupling the same diazo compound to N-
um(III), antimony(III), silver, and organic sub- methyl-N-cyanoethylaniline, Aizen Cathilon
strates, e.g., ascorbic acid [38]. Oleophilic acyl- Navy Blue GLH (Hodogaya) is obtained, and by
ated leuco compounds of diaminophenazine dyes coupling to N,N-dicyanoethylaniline, Sumiacryl
are suitable as color-forming agents in copying Navy Blue R (Sumitomo). These dyes have also
paper [39] and thermographic systems [40]. Ba- been recommended for dyeing polyacrylonitrile.
sic safranines can also be used in laser technology Similar dyes are used for determination of
[41] and in optical recording media with record- antimony or thallium by extraction of the ion
ing light having wavelengths shorter than 700 nm associate [46] and as thermosensitive color in-
[42]. dicators [47]. They also serve as lustering agents
Monoamino- and diaminophenazine dyes in galvanic copper-plating baths [48] and as
bearing at least one phenyl residue on an amino accessories in electrolytic tin plating [49]. Safra-
group, in the form of their anhydro bases, are nine azo dyes are also used in color photography
recommended for spin dyeing of polyacryloni- [50]. By diazotizing Rhoduline Violet and boil-
trile fibers in the gel stage [43]. ing down the diazonium salt solution, polymeric
482 Azine Dyes Vol. 4

phenazine dyes are obtained, which are likewise water is added at 5  C. After stirring the mixture
used as lustering agents in galvanic copper-plat- for 15 min, a neutral solution containing the
ing baths [51]. sodium salt of 30.5 kg of aniline-4-sulfonic acid
in 290 L of water is added. The mixture is again
stirred for 15 min, then heated to 40  C and
2.2.3. Acid Safranine Dyes stirred for 15 min. After rapid heating of the
mixture to 80  C with live steam, 11 kg of sodi-
The introduction of sulfo groups converts safra- um carbonate is added. The reaction mixture,
nines whose amino groups are arylated into fast cooled to 70  C, is transferred to a 6000 L re-
violet- to blue-coloring wool dyes, which are duction vessel equipped with a propeller stirrer,
especially suitable for seawater-fast bathing suits mixed with 50 kg of iron filings, and stirred for
and piece goods (women’s fabrics). Today the 45 – 60 min. The alkaline spot test must show a
importance of these dyes has decreased. They are blue rather than a reddish violet spot. The reac-
synthesized from sulfo-containing aniline and tion mixture is allowed to settle, then filtered
1,4-phenylenediamine derivatives by oxidation through a filter press. The process of settling and
to the indamine and cyclization to the azine by filtration is repeated and the press is then washed,
using a primary aromatic amine. If 1,3-dianili- first with 1000 and then with 2000 L of water.
nonaphthalene-8-sulfonic acid is used instead of The filtrate is salted out with 800 – 850 kg of
the aniline component, an indamine is obtained common salt and, after stirring overnight at 18 –
that already contains the nitrogen atom required 20  C, filtered under suction. After drying under
for the formation of the azine ring, so that in this vacuum, 180 – 190 kg of the dye is obtained,
case a third component is unnecessary. A further corresponding to 360 – 380 kg of commercial-
route to acid safranine dyes is the exchange of the type Acid Cyanine BF.
sulfo group in the 6-position in isorosinduline di- Other trade names were Acilan Fast Dark Blue
and trisulfonic acids in neutral or weakly alkaline BF and Aciderm Cyanine EZB (Bayer).
medium for the sulfonic acids of N-alkylated 1,4- On this basis reactive dyes for cotton have
phenylenediamines. The oxidative condensation been developed. Instead of aniline-4-sulfonic
of alkylated phenylenediamines with isorosindu- acid, 4-chloro- or 4-methoxyaniline-3-sulfonic
line bases followed by sulfonation is also used. acid has been used in this preparation procedure.
An example for an acid safranine dye made The primary amino group is then allowed to react
from three components is Acid Cyanine BF 26 with cyanuric chloride, 2-methoxy-4,6-dichlor-
(Agfa, 1906) [51], C.I. 50 230 [6448-97-1]. otriazine, or 2,6-dichloro-5-cyanopyrimidine
[53]. The dyes obtained by reaction first with
cyanuric chloride and then with 3-aminobenze-
nephosphonic acid or by reaction first with 2,4-
dichlorotriazine and then with aliphatic or aro-
matic amines containing a sulfatoethylsulfonyl
group are also recommended as reactive dyes for
cotton [54].
Commercial products of this series were Pro-
cion Blue MX-7RX, PN PC, T-7RX (ICI).
The acid safranine dyes that are obtained by
Preparation [52]. Neutral solutions con- joint air oxidation of 1,3-bis(phenylamino)-
taining the sodium salt of 61 kg of 4-nitro-40 - naphthalene-8-sulfonic acid and 4-aminodiphe-
aminodiphenylamine-2-sulfonic acid in 500 L of nylamine-2-sulfonic acid or 1,4-diaminoben-
water and the sodium salt of 57 kg of N-ethyl-N- zene-2-sulfonic acid in the presence of copper
benzylanilinesulfonic acid in 300 L water are oxide/ammonia still had significant sales about
combined in a 5000 L wooden vat equipped with fifteen to twenty years ago [55].
a propeller stirrer. After the solution has been Supranol Blue BL (27, R ¼ H) [6378-88-7]
diluted with 1400 L of ice water, a solution and GL (27, R ¼ OCH3) [6856-08-2], or Wool
containing 75.5 kg of sodium dichromate and Fast Blue BL and GL, C.I. 50 315 and 50 320,
37.2 kg of sulfuric acid monohydrate in 4000 L were the most important dyes of this series. Of the
Vol. 4 Azine Dyes 483

latter about 40 t were produced in the Federal sulfonic acid and 4,40 -diamino-30 -methyldiphe-
Republic of Germany in 1984. nylamine-2-sulfonic acid [58].

The primary amino group can react with

Preparation [55]. Weakly basic solutions cyanuric chloride [59] or with cyanuric fluoride
containing 0.87 kmol of 1,3-bis(phenylamino) and subsequently with aminobenzenesulfonic
naphthalene-8-sulfonic acid in 1700 L of water acid [60] to give reactive dyes which dye cotton
and 0.9 kmol of 4-aminodiphenylamine-2-sul- in clear blue shades.
fonic acid in 1000 L of water are combined in The condensation that takes place during the
a 10 000 L iron kettle equipped with a propeller formation of Acilan Fast Violet FB, or Wool Fast
stirrer (95 rpm), and a solution containing 35 kg Violet B 29, C.I. 50 325 [6837-46-3], from 1,3-
of copper sulfate and 40 kg of 40 % ammonia in bis(phenylamino)naphthalene-8-sulfonic acid
130 L water is added, followed by 40 kg of and 2-methoxy-1,4-phenylenediamine-5-sulfon-
ammonium chloride and 3500 L of ethanol. Af- ic acid proceeds differently. In the cyclization
ter dilution to 7000 L with water, air is blown step the methoxy group is split off as methanol.
through the mixture at 40  C for 6 h. Then, the Therefore, the dye can also be synthesized from
reaction mixture is allowed to cool to 25  C and 1,4-phenylenediamine-2-sulfonic acid.
salted out with 2000 L of 25 % common salt
solution. After the mixture is filtered through a
suction filter under pressure, the press cake is
washed twice with cold water. Yield: 500 kg
¼ 1350 kg Supranol Blue BL, commercial type.
Other trade names were Aciderm Blue EBL
(Bayer), Benzyl Blue BL [6378-88-7], Orasol
Blue BLN [52218-73-2] (Ciba-Geigy), Coomas-
sie Blue BL (ICI), and Xylen Fast Blue BL
(Sandoz). By reaction with longer chain aliphatic
Supranol Blue BL can be converted to a spirit- amines, the spirit-soluble dye Irisol Fast Violet
soluble form by reaction with longer chained BBN [71839-03-7] is obtained.
aliphatic amines. Such a dye salt was commer- Dyes of the type of formula 27 or 29 can be
cially available as Irisol Fast Blue BLN [6378- used as main component in blue toners for the
88-7] for dyeing nitrocellulose lacquers. This dye electrophotography [61] or as tinting dyes in
is also suitable for dyeing and printing of syn- fluorescent whitening.
thetic polyamides from organic solvents, in par- Supranol Fast Cyanine B or Indocyanine B 32,
ticular chlorinated hydrocarbons [56]. Supranol C.I. 50 335 [6378-89-8], (Agfa, 1902), is syn-
Blue GL is similarly used to prepare Irisol Blue thesized by the following reaction sequence: 2-
GLE. The dyes can be reduced to leuco com- phenylaminonaphthalene is condensed with 4-
pounds, which can be used to check the packag- nitrosoethylbenzylaniline to give the indamine,
ing of foodstuffs stored under oxygen-free con- which is oxidized with manganese dioxide to the
ditions with regard to imperviousness of the isorosinduline (Blue I, 30). Subsequent reaction
packaging [57]. with 4-aminodiethylaniline and 4-nitrosodiethy-
Wool Fast Blue FFG 28, C.I. 50 330 [6837- laniline gives the safranine (Blue II, 31), which is
47-4], is prepared, analogously to Supranol Blue then disulfonated to 32 [62]. The dye is used as an
BL, from 1,3-bis(phenylamino)naphthalene-8- accessory for the galvanization of copper [63].
484 Azine Dyes Vol. 4

Supramine Blue EG was selected as Standard

4 for the eight-step ISO lightfastness test [65].
The dyes Novazol Acid Blue GL (36, R ¼
C2H5) and Polar Blue G (36, R ¼ CH2C6H5),
developed by Geigy, are obtained from diethy-
lisorosinduline-1,6-disulfonic acid 35, prepared
according to [66], by exchange of the sulfonic
group in the 6-position for 4-aminodiethylani-
line-3-sulfonic acid and 4-aminoethylbenzylani-
line-3-sulfonic acid [67], respectively. The sec-
ond sulfo group in the 16-position can also be
introduced by sulfonation in oleum [68]. This
improves the alkali fastness and shifts the tint
form a dull reddish blue to a pure greenish blue.

Fast Wool Blue EB 33, C.I. 50 300 [6471-74-

5], and Supramine Blue EG 34, C.I. 50 310
[6378-87-6], are prepared according to the same
method [64].

Acid safranine dyes, e.g., 33, are recom-

mended for use in inks for ink-jet printers [69].
They are useful as indicators in the quantitative
analysis of metal ions such as As(III), Sb(III), Tl
(I) and organic substrates like hydroquinones and
ascorbic acid [70]. They have also been com-
bined with monomeric acrylic acid derivatives or
unsaturated polyesters, and deep-colored poly-
mers have been prepared in this way [71].

2.2.4. Indulines

Induline dyes, the product of the reaction of

aniline hydrochloride and aminoazobenzene,
consist of a complex mixture of phenazine dyes,
the composition of which continuously changes
with progressive reaction. Induline 6B 43, which
is substituted with four aniline groups, is finally
Vol. 4 Azine Dyes 485

formed. The reaction begins with the reduction of Induline Base 5BM consists of a mixture of the
4-aminoazobenzene to 1,4-phenylenediamine, above-mentioned induline dyes, Induline base
which is oxidized to the quinone imine. Then, 6B being the main component.
addition of aniline and oxidation to give the Induline Base 6B was synthetically prepared
quinone alternate until 2,5-dianilinobenzoqui- by an independent route by condensation
none-1,4-iminemonoanil 37 and -dianil (39; azo- of 4,5-bis(phenylamino)-o-benzoquinone with
phenine) are formed. After azine ring closure and 2-amino-5-chlorodiphenylamine followed by
oxidation, 37 gives induline (38; Hoechst, 1889), reaction with aniline hydrochloride [72].
while 39 is converted to aminophenylaposafra- Indulines which are soluble in benzene or
nine 40. spirit are synthesized by alkylation [73], e.g.,
with alkyl halides [74].
Induline bases are primarily used for dyeing
of plastics. They are recommended as charge-
controlling agents in positive toners for electro-
photography [75]. Salts with oleic acid can
be used in typewriter ribbons or carbon
paper [76].
By sulfonation of the bases, acid induline dyes
are obtained, which are used for the dyeing of
leather. They are useful for improving the light
stability of photographic paper [77] and for
adjusting the contact angle of inks for ink-jet
applications [78].

In addition, the following dyes could be iden-

tified in the induline melt: Indamine Blue B, R, 2.2.5. Nigrosines
Nigrosine Base G 41 (BASF), C.I. 50 204 [6471-
73-4], Induline Base 3B, Fast Blue Base RF 42 Nigrosine dyes, the products of the action
(BASF), C.I. 50 400 [8004-98-6], Induline Base of nitrobenzene on aniline in the presence of
N (BASF), Induline Base 6B 43, C.I. 50 400 iron(II) chloride and hydrochloric acid, also
[8004-98-6]. consist of a complex mixture of phenazine dyes.
The thin-layer chromatogram shows a large
number of components that are also present in
induline, in particular Induline 6B 43. In con-
trast to induline, however, the dye mainly con-
sists of higher molecular mass phenazines,
which remain at the starting spot of the
chromatogram.
A distinction can be made between water-,
ethanol-, and fat-soluble nigrosines. The ratio of
aniline to nitrobenzene and the melting tempera-
ture differ only negligibly for the three kinds. The
crude melt, a mixture of nigrosine hydrochlor-
ides, is offered as Phenol Black L for the dyeing
of phenolic resins.

Preparation. In a 3000 L steel enameled

kettle equipped with a stirring apparatus, an
indirect heater, and a 3.0 MPa steam heat
exchanger, 2000 L of aniline, 231 L of 30 %
hydrochloric acid, and 132 kg of iron(II) chloride
486 Azine Dyes Vol. 4

are heated over 2 – 3 h to 165  C, and the water, followed by treatment with caustic soda, is
together with azeotropically codistilled aniline, heated to 240  C and extruded into cold water
is distilled. Over 5 h, 588 L of nitrobenzene is through a 3 mm nozzle [83]. By the addition
introduced at 165  C with stirring. Because of the of phthalic anhydride to the nigrosine melt,
exothermic reaction, the temperature increases to a readily dispersible, flowable form is ob-
170 – 180  C; it is then adjusted to 186  C over tained [84].
the course of 4 h, and maintained for 2 – 3 h at The replacement of 5 – 15 % of the aniline
this temperature. The melt is subsequently dilut- with o-nitrochlorobenzene supposedly results
ed with 1400 L of aniline and drawn off into in better yields for the nigrosines and indu-
4000 L of water which has been placed in a lines [85].
6000 L steel enameled kettle equipped with a The nigrosine bases serve for preparation of
stirring apparatus. The reaction kettle is washed printing colors and for dyeing of plastics. They
with 100 L of aniline, and this, along with the are used as broadband-absorbers in thermal opti-
aniline water from the distillation condenser, is cal limiters for laser application [86] and as
added. The reaction mixture is now heated to additives in the dispersion polymerization of
95 – 100  C and stirred for 1 h at this tempera- styrene and butyl methacrylate to yield mono-
ture, and the charge is allowed to stand for 24 – disperse micrometer-size beads with narrow size
36 h to separate the phases. The lower layer is distribution [87].
drawn off into a 4000 L paddle dryer; the upper The preparation of water-soluble nigrosines
aniline – water layer is fed to an aniline recovery starts from the crude nigrosine melt. In this
unit. In the paddle dryer, the melt is heated in a case, the preparation is similar to that of
vacuum of 27 kPa with steam of 100 kPa over- Phenol Black L; however, before evaporation
pressure to 100  C jacket temperature. After 2 – in a paddle dryer, the hydrochlorides are
3 h, the temperature is increased to 140  C and converted to the base by treatment with caustic
maintained at this temperature for 18 h. The melt soda. In order to facilitate separation of the
is cooled over 6 h, the vacuum lifted with nitro- aqueous phase, the viscous melt is first diluted
gen, and the paddle dryer emptied. Yield: with aniline.
1150 kg Phenol Black L; 2700 kg of aniline is By sulfonation of the thus-prepared Lake
recovered. Black Crude, Nigrosine WLF and W liq.
The preparation of nigrosine dyes can also be [8005-03-06] are obtained.
carried out continuously by passing the reaction The dyes serve for the dyeing of paper and
melt successively through two reaction zones at leather [88]. They are used as cheap darkening
different temperatures. In the first zone, the melt agent for olives [89]. Arylguanidine salts of
is heated for 6 h at 150 – 160  C, and in the sulfonated nigrosines, e.g., with di-o-tolylguani-
second for 12 – 13 h at 180 – 200  C [79]. The dine, afford ballpoint pen inks with black shades
workup of the nigrosine melt can also be carried having high color strength. They exhibit infrared
out continuously by mixing the aniline-contain- absorption [90].
ing dye melt with an aqueous medium and sepa- Nigrosine dyes containing sulfonic acid
rating the aqueous phase from the aniline- groups can also be prepared by treating nigrosine
containing phase in a suitable separation bases with diazotized sulfanilic acid in the pres-
apparatus [80]. ence of pyridine, adjusting the pH to 10 by the
Removal of excess aniline can be carried addition of alkali, separating the pyridine base,
out by grinding the melt with aqueous acid in and salting out the dye. This dye is used for ink-
a ball mill [81]. A pyrophoric nigrosine base jet printing [91]. Ammonium salts of the nigro-
can be freed of this disadvantageous property sine sulfonic acids serve for the preparation of
by dissolving it in aniline and introducing waterproof flexographic inks [92]. Solutions of
air for 16 h at 75  C. Subsequently, the solution acid nigrosine dyes containing a polyvinylpyrro-
is evaporated to dryness under vacuum [82]. lidone resin are aqueous printing colors for ink-
A nigrosine granulate is obtained if the nigro- jet printing [93].
sine melt, prepared by reaction of aniline The ethanol-soluble nigrosines are the puri-
with p-tert-butylnitrobenzene at 180 – 185  C, fied hydrochlorides of the nigrosine bases.
Vol. 4 Azine Dyes 487

Complete removal of the iron salts is a determin- black brands are obtained. Important commercial
ing factor for the solubility in spirit. Important products are Nigrosine Black BA liq., Nigrosine
commercial products are Brilliant Spirit Black Black A liq. (Bayer/Lanxess), Neptune Black
RM, Lake Black H (Bayer/Lanxess), and Basonyl X14, X16 (BASF).
Black X22 (BASF). Such dyes are useful for ink-jet application
[95]. Salts of organic acids or acylated nigrosines
Preparation of Brilliant Spirit Black RM are suitable as developers for electrostatic copy-
New. In a 1000 L cast-iron melting kettle ing processes [96] and as colored charge-control-
equipped with a gate agitator, a condenser, and ling agents in positive toners for electrophotog-
a heating coil (2.5 MPa steam), 570 kg of ani- raphy [97].
line, 182 kg of 30 % hydrochloric acid, 16 kg Nigrosine salts of long-chain alkyl sulfonic
of dry iron(II) chloride, and 16 kg of iron acids, prepared by reaction of nigrosine bases
turnings are slowly heated to 120 – 125  C with these acids, are used for oil-soluble inks [98]
with stirring until the water is distilled off. or in microencapsulated form for pressure-sensi-
Then, the reaction mixture is rapidly heated to tive copying material, which can be read in the
180  C, 180 kg of nitrobenzene is added in a infrared [99].
thin stream over 4 – 5 h at this temperature, and Induline and nigrosine dyes containing
the mixture is maintained for an additional 3 h at sulfonamide groups are prepared by reaction
180 – 185  C inner temperature. The reaction of induline and nigrosine sulfonyl chlorides
water together with some nitrobenzene and with primary and/or secondary aliphatic or
aniline is distilled off through a descending cycloaliphatic amines. They are suitable for
condenser. The nitrobenzene – aniline mixture, the preparation of lac and printing dyes, ball-
which separates from the water, is returned for point pen pastes, and mimeographic colors
reuse in the reaction process. After completion [100].
of the melting, the contents of the kettle are Spirit-soluble nigrosines, which are especial-
transferred to a 7000 L stone-lined cast-iron ly valuable for the preparation of inks and ball-
kettle equipped with a mechanical stirrer and point pen pastes, are obtained by reaction of
containing 1500 L of water and 500 L of 30 % nigrosine bases with propylene oxide or butylene
hydrochloric acid. The charge is stirred for 8 h oxide [101].
at 95  C and pressed hot in filter presses; the
press cake is washed with water to remove the
aniline, boiled with 1500 L of water and 75 kg
of 30 % hydrochloric acid for 2 h, pressed 2.2.6. Aniline Black
out, and washed to neutrality. After drying
under vacuum at 90  C, 330 kg of Brilliant Aniline Black [13007-86-8] is the term for a
Spirit Black RM New is obtained. By neutrali- group of dyes that are formed by oxidation of
zation of the salt liquor with lime followed aniline, o-toluidine, m-toluidine, p-phenylene-
by steam distillation, 340 kg of aniline is diamine, 4-aminodiphenylamine, and similar
recovered. bases of the benzene series. The involved struc-
An ethanol-soluble nigrosine granulate is pre- tures were the subject of several studies. It is
pared by first treating the washed, wet nigrosine believed that, starting from indamine structures
paste with a paraffin wax melt in the presence of such as emeraldine 44, further oxidation and
nonionic surfactants, then drying and grinding condensation with aniline form phenazine
[94]. structures like 45 and 46 and finally insoluble
The fat-soluble brands consist of the nigrosine polymeric compounds [102]. Aniline Black is
bases that have been obtained from the hydro- mostly produced on the fiber itself in printing
chlorides by treatment with soda. Commercial and in dyeing; for example, on cotton as well as
products are Nigrosine Base BA (Bayer/ on synthetic fibers, especially polyester fibers.
Lanxess). In addition, for the dyeing of lacquers, plastics,
By heating the nigrosine bases with fatty acids and paper Aniline Black is produced in
such as stearic acid or oleic acid, fat-soluble substance.
488 Azine Dyes Vol. 4

For the one-bath dyeing of cotton yarn, the Resolin Black Base, Bayer), which are oxidized
fibrous material is treated with a solution of by quinonedichloroimide (e.g., the former Reso-
dichromate, aniline, hydrochloric acid, sulfuric lin Black Developer, Bayer) [106].
acid, and copper sulfate, first in the cold, then at Helio Fast Black TW, a color-strong Aniline
70  C. Finally, the material is washed and Black pigment, is obtained by replacing part of
soaped. This black color greens under the influ- the aniline with o-toluidine. The pigment con-
ence of reducing agents. According to another tains a significant amount of chromium, which
dyeing process, the cotton fabric is placed in a comes from the oxidizing agent sodium dichro-
bath containing aniline, aniline hydrochloride, mate; the amount can be decreased by stirring
sodium chlorate, ammonium chloride (as acid with 3 % hydrochloric acid.
source), aluminum acetate, and a copper or va-
nadium salt as catalyst. The fabric is padded, Preparation. 3750 L of water and 436 L of
dried, steamed, then possibly treated with chro- 30 % hydrochloric acid are placed in a 8000 L
mium salts to complete the oxidation, and finally enameled kettle equipped with a mechanical
soaped. The colors thus obtained possess better stirrer, and 150 kg of aniline and 52 kg of
fastness properties. To protect the fibers from o-toluidine are then added. With further stirring,
damage by the mineral acids present, nonpreci- 78 kg of sulfuric acid monohydrate is added, and
pitable proteins, urea, and dextrose have been the contents of the kettle are heated to exactly
recommended [103]. The general dyeing proce- 27  C. Starting at this temperature, a 24.5 %
dure is described in [104]. Improvements have solution of sodium dichromate is added in several
been made by avoiding the steaming step, which portions, and the solution is stirred each time for
results in energy conservation and reduction of 15 min before the next amount follows. The
air pollution by aniline vapor [105]. temperature increases to 29  C with the addition
The production of black tints on polyester of 318 kg of sodium dichromate solution; further
materials can be achieved with soluble deriva- addition of three times 273 kg raises the temper-
tives of 4-aminodiphenylamine, e.g., azo- ature to 33, 39, and 45  C. Then the pigment is
methines of sulfobenzaldehydes (e.g., the former immediately isolated in a filter press, washed
Vol. 4 Azine Dyes 489

with 3000 L of water, and dried by blowing. The ride, permanganates, hypochlorites, or dichro-
dried pigment is mixed with 6000 L of deionized mates. Because the small dye precursors pene-
water and 500 L of 30 % hydrochloric acid and trate deep into the hair and are oxidized there to
stirred overnight at 25  C. The press cake is larger colored compounds, the coloring is ex-
washed with 8000 L of distilled water, and the tremely durable to light and washing. The Ursol
pH of the mixture is raised to 5 with 5 kg of dyes, developed by Agfa, by Farbwerke Hoechst,
sodium carbonate. The isolated product is dried and later by IG Farbenindustrie, were produced
under vacuum at 90 – 95  C. Yield: 280 kg He- in the past, e.g., by BASF and are now produced
lio Fast Black TW. by Dohmen. They also contain, besides diamines,
An ash-poor Aniline Black is obtained by aminophenols and their nitro and chloro deriva-
oxidizing aniline with potassium dichromate in tives as well as their salts with hydrochloric and
the presence of copper(II) sulfate and sulfuric sulfuric acids.
acid; the dichromate and sulfuric acid are added
in three portions over 5 h at 50  C [107]. The Fur Dyes. The most important dye is Ursol
oxidation can also be effected with sodium hy- D or Benzofur D [106-50-3], 1,4-phenylenedia-
pochlorite instead of potassium dichromate mine. Other brand names were or are, e.g., Pe-
[108]. Finally, a chromium-free Aniline Black lagol D, Pelagol Grey D, Peltol D, Tertral D,
can also be obtained by oxidation, first with H2O2 Durafur Black R, Fouramine D, Furro D, Futra-
in the presence of copper sulfate, and subsequent- mine D, Nako D, Developer PF. On oxidation, it
ly with atmospheric oxygen [109]. is converted via the quinoneimine into
A black pigment having a similar constitution Bandrowski’s Base 48, X ¼ NH), which, on
is formed by oxidation of o-ethylaniline with further oxidation, forms phenazine dyes [117].
sodium chlorate in acidic medium in the presence
of copper sulfate [110].
Aniline Black is used in dry toners for elec-
trophotographic laser printers [111], in ! pig-
ment inks for ink jet printers [112], and bound to a
protein in the production of an antiserum for
cancer therapy in warm-blooded animals. Ani-
line Black is an electrical conductor with holes as
the main charge carriers [113]. It can act as the
cathode material of rechargeable lithium batter-
ies [114].

2.2.7. Oxidation Dyes

Oxidation dyes are organic compounds that are

converted into the dyeing substance on the sub-
strate being dyed. They are used for dyeing furs
because with these products the natural character
of fur pelts can be especially well imitated or
improved on. Today they are increasingly being
displaced by acid dyes, but especially the luster Ursol D is also present as a component in
and coverage of oxidation dyes are still superior. numerous other Ursol dyes, e.g., Ursol A, DF,
In their fundamental patents MONNET in 1883 DG, NZ, NZD, RH, RHG, SK, and SKG.
[115] and ERDMANN in 1888 [116] made known a p-Aminophenol is commercially available as
process for dyeing hair and feathers with aqueous Ursol P or Benzofur P [123-30-8]. On oxidation,
or alcoholic solutions of aromatic diamines in it forms first the quinonemonoimine, which,
which the dyeing substances, after being ab- following an analogous path as described above,
sorbed by the material, are oxidized with atmo- yields hydroxy compound 48 (X ¼ O), which
spheric oxygen, hydrogen peroxide, iron chlo- is analogous to Bandrowski’s Base. This is
490 Azine Dyes Vol. 4

converted into oxazine compounds on further mine, and 60 % consists of a mixture of the
oxidation [118]; cf. [4]. sodium salts of the sulfonic acids obtained by
Some Ursol dyes, such as Ursol EG (m-ami- sulfonation of coconut oil monoglyceric esters
nophenol) [591-27-5], Ursol EWG (chlororesor- and naphthalene with fuming sulfuric acid (10 %
cinol and resorcinol), Ursol ERN (1-naphthol) SO3). Important Ursatin dyes are Ursatin Brown
[90-15-3], and Ursol SLA (2,4-diaminoanisole B, Yellowish Brown G, Blue RN, Violet B, and
sulfate) [6219-67-6], have inherently only a Red BB.
small dyeing ability, but in combination with Other fur assortments were Nako (Hoechst),
other Ursol dyes effect a deepening as well as Durafur (ICI), Fourramine (Francolor), Euka-
a shifting of the color shade; e.g., Ursol EG shifts mine (Geigy).
gray to blue and black to olive brown. Only with
such or similar combinations are pure blue or red Cosmetic Hair Dyes. For cosmetic hair
shades available [119]. Substituents in the 4- dyes, the oxidation dyes are commercially avail-
position in such m-disubstituted benzenes stop able in the form of solutions or pastes. Ursol dyes
further condensation on the level of indamines or used for this purpose include Ursol D, Ursol 4G
indophenols 49. Fur dyeing with simultaneous (1-nitro-3,4- diaminobenzene hydrochloride),
silvering of hair ends is achieved by treatment Ursol 4R wet (picramic acid), Ursol 2G (2,4-
with metal salts, 4-amino-2-methoxydiphenyla- toluylenediamine), Ursol P-Base, Ursol Brown
mine, and a condensation product of formalde- RR (2-nitro-1,4-phenylenediamine) [5307-14-2],
hyde with resorcinol and cresolsulfonic acid Ursol EG, and Ursol EWG. For a historical
[120]. review, see [121].
Azine and oxazine dyes are obtained on oxi-
dation of equivalent amounts of diaminoben-
zenes or aminophenols and dihydroxybenzenes
with hydrogen peroxide, the skin-irritating
Bandrowski’s Bases being avoided. (Example:
2-methyl-1,4-phenylenediamine and resorcinol
[122]). By preoxidation of a molar mixture of
a 1,4-diamine (e.g., 2,5-toluylenediamine) and
either a 1,3-diamine (e.g., 2,4-diaminoanisol), a
1,3-aminophenol, or a 1,3-dihydroxybenzene
with 1 – 2 mol of O2, a colored preparation is
obtained [123] that produces permanent hair
colors [124].
Commercial products of this series were Ursol
NZS and Ursol RHS (BASF).
Aminophenols [125] and diaminophenol
ethers [126] that bear a methyl group on the
aromatic ring can be used as coupling compo-
nents in hair coloring agents. 1-Methyl-4-isopro-
pyl-2-hydroxybenzene is also recommended as a
coupling substance [127]. The tolerance of skin
toward the couplers based on phenylenediamine
is improved by the introduction of alkyl ester
groups into the benzene ring [128] or into the
The Ursatin dyes, introduced commercially in amino group [129] or by alkylation of the amino
1935 by IG Wolfen, can also be used to effect group [130]. The introduction of sulfo groups
combinations of shades. These are the salts of serves the same purpose. N,N-bis(2-hydro-
dihydroxynaphthalenes with aromatic or hetero- xyethyl)-p-phenylenediamine is used as a partial
cyclic amines. Ursatin Brown B has, e.g., the replacement for p-phenylenediamine [131].
following composition: 40 % of the salt consists Aminonaphtholmonosulfonic and -disulfonic
of 1,5-dihydroxynaphthalene and toluylenedia- acids are used as couplers [132].
Vol. 4 Azine Dyes 491

4-Amino-3-methylpyrazolone hydrochloride 2.3. Aminohydroxy- and

and its N-substituted derivatives [133] as well Monohydroxyphenazine Dyes
as 3-aminopyrazoline [134] are physiologically
compatible heterocyclic amines for dyeing hair. Phenazine dyes with an amino and a hydroxy
An example of a heterocyclic hydroxy compound group as auxochromes are virtually completely
is 6-hydroxyquinoline [135]. 2,4,5,6-Tetramino- present in the phenazone structure (1c, where D2
pyrimidine as developer and 2,6-diaminopyri- is ¼O). They are obtained by reaction of nitro-
dine as coupler yield shades with high vividness sophenols with m-toluylenediamines that are
and excellent fastness [136]. The same is true alkylated in the position para to the methyl group
of hydroxyaminopyrimidines, e.g., 2-hydroxy- to give indophenols, followed by oxidation to
4,5,6-triaminopyrimidine [137], and diamino- give the azine dye. Dyes of this kind having a
pyrazoles [138], which additionally have excel- naphthalene ring system are obtained if the iso-
lent physiological tolerance properties. 6-Ami- rosinduline dyes, prepared from alkyl- or aryl-2-
no-2,2-difluoro-1,3-benzodioxole is a coupler naphthylamines and nitrosodialkylanilines, are
with improved fastness to washing and light and treated with alkali under the action of oxygen.
good substantivity [139]. None of these dyes has industrial importance any
Also suitable for hair dyeing are indamines, more. However, phenazone compounds have
indoanilines, and indophenols, the initial reac- been suggested for the delignification of ligno-
tion products of the hair dyes described above. cellulose materials [153]. Their use in recording
Indamine salts are formed by the joint oxidation materials has also been described [154].
of aromatic diamines and aminohydroxy com-
pounds [140]. Indamines with ring-cyclized
amino groups are obtained by the use of 6- 3. Oxazine Dyes
hydroxytetrahydrobenzoxazine [141]. The joint
oxidation of phenylenediamine and phenols by The cationic mono- and diaminophenoxazine
ammonium persulfate affords the indaniline dyes dyes are widely used to dye acid-modified syn-
[142]. Their leuco compounds, the aminohydrox- thetic fibers, especially polyacrylonitrile fibers
ydiphenylamines, are also suitable as hair dyes containing acid groups [155]. Aminophenoxa-
[143]. Indophenols are formed by the joint oxi- zine dyes are also suggested for dyeing polyolefin
dation of aminophenols and phenols [144]. materials [156]. The earlier areas of application,
In the 1980s several compounds for cosmetic the dyeing of tannin-mordanted cotton, silk,
hair dyes have been banned in Europe for toxi- leather, and lacquers, are now only of minor
cological reasons, including 2,4-diaminotoluene importance.
and 2,4- and 2,5-diaminoanisole. Substitutes The aminohydroxyphenoxazine dyes include
have been found, e.g., 2,4-diaminophenoxyetha- the gallocyanines, which form light-stable metal
nol [145], 2-amino-4-b-hydroxyethylaminoani- complexes with chromium. They were mainly
sole [146], 1,3-bis(2,4-diaminophenoxy)propane used for the dyeing and printing of wool, but also
[147], 2-b-hydroxyethyl-p-phenylenediamine for the dyeing and printing of cotton; however,
[148], and 3,4-diaminophenols bearing ami- they have been replaced by acid anthraquinone
noalkyl or mono-, di-, or trihydroxyalkyl sub- dyes and by reactive dyes.
stituents on the N and O atoms [149]. Diaminophenoxazine dyes have recently
A new study shows a significant increase of found application in laser technology. They com-
bladder cancer caused by the repeated use of plement the emission spectrum of rhodamine on
permanent (oxidation) hair dyes over several the long-wavelength side [157].
years [150]. Phenoxazine dyes function as desensitizers
Because the use of hydrogen peroxide at high [158] and are used in optical recording media
pH damages the hair and irritates the scalp, with recording light having wavelengths shorter
procedures using oxidative enzymes instead of than 700 nm [42]. Leuco phenoxazine dyes
peroxides have been developed which work at are used in acylated form as chromogenic
neutral pH values [151]. Oxidoreductase en- substances in pressure-sensitive copying
zymes are recommended for the same reasons paper. In a photochemical oxidation step, an
[152]. acyl group is split off and blue dyes are formed.
492 Azine Dyes Vol. 4

The benzoyl derivatives are preferably used

[159]. However, the acyl moieties of aliphatic
carboxylic acids are also applied [160]. Suitable
acylating agents include heterocyclic carboxyl-
ic acids derived from pyridine, furan, or thio-
phene [161]. These leuco derivatives can be
used in electrically developable recording ma-
terials [162] and in dye transfer printing pro- Preparation. 100 kg of dimethylaniline,
cesses [163]. dissolved in 260 kg of 30 % hydrochloric acid,
Aminophenoxazine dyes [164] and hydroxy- is nitrosated with 58.4 kg of sodium nitrite in the
phenoxazine dyes [165] are also suitable in form of a 40 % solution at 3 – 5  C over 8 –
the form of their leuco compounds as highly 10 h. The reaction mixture is stirred for 1 h and
sensitive oxygen detectors. The dyes are allowed to stand overnight. It is then suction
also used for the analytical determination of filtered and the product is washed with a dilute
ascorbic acid [166] and as anodic electrochro- solution of common salt and finally with 200 L of
mic materials in electrochromic devices such as ethanol. The nitroso compound, wet with etha-
rearview mirrors, sun roofs, or windows nol, is made into a paste with 77 kg of zinc
[167]. chloride and 250 – 300 L of ethanol and during
Furthermore, diaminophenoxazine dyes are 90 – 95 min added in 35 – 40 portions to a
used for the staining of preparations in micros- boiling solution containing 90 kg of 2-hydroxy-
copy. They have recently also become of interest naphthalene in 400 L of ethanol. The product is
in chemotherapy. Compounds such as 51 are filtered hot through a closed suction filter under
thought to inhibit tumor growth and to be effec- pressure, washed with a dilute solution of com-
tive against tubercular bacilli. The activity of mon salt containing zinc chloride, dried by suc-
several dyes exceeds even that of streptomycin tion, and made into a paste in a mixer with
[168]. 13.2 kg of dextrin (to bring to commercial stan-
dard) and 5.4 kg of machine oil (to free from
dust), and dried for 90 h at 55 – 60  C.
Yield: 185 – 192 kg of commercial product.
Moreover, the intermediate isolation of the ni-
troso compound can be eliminated [169].
The dye was offered as Leather Dark Blue
H3R (Hoechst) and, for the dyeing of polyacry-
lonitrile, in dye mixtures. Furthermore, it is
reported to be an intermediate hydrogen carrier
for the determination of glucose-6-phosphate
dehydrogenase [170] and a colored charge-con-
trol agent in toners for electrophotography [171].
The dye synthesized in a similar way from ni-
3.1. Monoaminophenoxazine Dyes trosodiethylaniline is used in a solid laser com-
position [172].
Monoaminophenoxazine dyes are synthesized by Blue to black dyes suitable for dyeing cellu-
reaction of nitrosodialkylanilines with aromatic lose acetate are obtained by condensation of
hydroxy compounds, in particular compounds of nitrosodimethyl- or diethylaniline hydrochloride
the naphthalene series. with 1,5-dihydroxynaphthalene in aqueous alco-
Fast New Blue 3R 52, C.I. 51 175, first de- holic solution containing at least 30 % water,
scribed in 1879, is the reaction product of 2- preferably with the addition of manganese diox-
naphthol with excess 4-nitrosodimethylaniline, ide as catalyst [173]. The presence of water is
which functions simultaneously as oxidizing necessary; otherwise, gray dyes are formed.
agent. It is used for dyeing polyacrylonitrile and, The position para to the nitrogen atom in the
mixed with brown or yellow basic dyes, for the naphthalene ring is activated. By reaction with
production of black tints on leather. amines, entry is achieved into the series of
Vol. 4 Azine Dyes 493

diaminophenoxazine dyes (see Section 3.2). By solution containing 125 kg of N,N-diethyl-m-

reaction with Michler’s hydrol [bis(4-dimethy- aminophenetidine in 150 kg of ethanol and
laminophenyl) methanol] Fast New Blue R 168 kg of 30 % hydrochloric acid at 0 – 3  C.
(Bayer, 1892) is obtained. Sulfur-containing sub- After the solution has been stirred for 1 h, 7.5 kg
stituents can also be introduced into this position; of soda is added to raise the pH to 2 – 4. The
e.g., Fast New Blue 3R can be treated with suspension obtained is added in small portions to
arylsulfinic acids, thiophenol, thiosalicylic acids, a boiling solution containing 100 kg of m-diethy-
thioacetic acid, or thiourea. The initially formed laminophenol in 300 kg of ethanol. When the
leuco compounds are oxidized with iron chloride reaction is complete, the mixture is cooled to
or nitric acid [174]. 50  C, 50 kg of zinc chloride is added with
stirring, the mixture is allowed to cool to 20  C,
and the dye is filtered off under suction in the
3.2. Diaminophenoxazine Dyes form of the zinc chloride double salt and washed
with ethanol. The wet suction-filter cake is sus-
Diaminophenoxazine dyes are synthesized by pended in 4000 L of water, and ammonium
reaction of nitrosodialkylanilines or nitroso- carbonate (ca. 90 kg) is added at 60  C until the
dialkylaminophenols with aromatic amines or filtered solution gives no more zinc carbonate
aminophenols in alcoholic solutions or mineral precipitate after further addition of ammonium
acids. They are characterized by very clear carbonate. The solution is filtered at 60  C and
hues. the readily soluble dye is isolated by spray
Rhodulin Pure Blue 3G 53 (Bayer, 1916), C. drying.
I. 51 004 [444-00-2], is obtained by the action of Addition of acetic anhydride during the con-
4-nitroso-1-diethylamino-3-ethoxybenzene on densation step is advantageous [176]. The nitro-
3-diethylaminophenol in alcoholic hydrochloric sation and further condensation to give the ox-
acid, whereby the ethoxy group is cleaved off. azine dye can also be carried out in a cyclic ether
(dioxane), in sulfolane, or in an alkyl-substituted
amide (dimethylformamide) [177]. If the con-
densation is carried out in the presence of zinc
chloride and zinc oxide in methyl glycol, the dye
precipitates directly as the chlorozincate in very
pure form [178]. Oxazine dyes like 53 can ad-
Rhodulin Pure Blue 3G, also called Oxazine
vantageously be isolated as bromide salts be-
725, is at present the most important cationic
cause of their low solubility. These low-salt
oxazine dye and is represented in all large assort-
products can be used directly for dyeing or for
ments of polyacrylonitrile dyes. Examples are
the preparation of liquid dye formulations, e.g.,
Aizen Cathilon Blue 5G (Hodogaya), Astrazon
by reaction with potassium acetate [179]. If the
Blue BG (Bayer/DyStar), Diacryl Brilliant Blue
condensation is done in a mixture of a water-
5G-E (Mitsubishi), Sumiacryl Blue E-6G (Sumi-
miscible solvent (dimethylformamide) with wa-
tomo), Maxilon Blue 5G (Ciba/Huntsman), Sev-
ter or an alcohol in the presence of nitric acid,
ron Blue 5G (Crompton & Knowles), and Yor-
pure dyes of high color strength are obtained as
acryl Blue 5G (Yorkshire).
nitrate salts [180]. Tetrachloroferrate salts can be
A similar product was Basacryl Blue MX-8GF
isolated in pure form and are recommended to
(BASF).
avoid contamination of wastewater with zinc
According to a newer preparation procedure
salts [181]. Liquid preparations can be obtained
for Rhodulin Pure Blue 3G, the intermediate
starting from chlorozincate salts by extraction of
isolation of the nitroso compound can be dis-
the salts of oxazine dyes with monocarboxylic
pensed with, and the dye is converted into the
acids into glycol ethers, while the metal is kept
hydrochloride by precipitation of the zinc as its
in the water phase by use of a complexing
carbonate.
agent [182].
Instead of 3-ethoxydiethylaniline, hydro-
Preparation [175]. 114 kg of a 40 % aque- xyalkyl ethers, prepared by reaction of 3-hydro-
ous solution of sodium nitrite is introduced into a xydiethylaniline with alkylene oxides, can be
494 Azine Dyes Vol. 4

used. This reaction can be carried out as the first Commercial products of this series were Re-
step of a one-pot procedure leading to the finished macryl Blue GGL (Hoechst) and Sevron Pure
dye [183]. The zinc-free dye is obtained by Blue 4G (Du Pont).
precipitation with urea or thiourea [184]. Diaminophenoxazine dyes with primary and
Rhoduline Pure Blue 3G tints are character- secondary amino groups are of particular indus-
ized by a frequently desired green shade in trial importance. Because of their low molecular
artificial light. The dye is therefore often used mass, they migrate on polyacrylonitrile fibers
in mixtures for dyeing polyacrylonitrile fibers in and therefore result in especially level dyeing.
blue [185] and black [186] tints. As the salt of the The dye 55 is prepared, e.g., by nitrosation of
dialkyl ester of sulfosuccinic acid, Rhodulin Pure 3-hydroxydimethylaniline and condensation
Blue 3G is used for dyeing acid-modified poly- with 2,4-diaminoanisole [201] or with 2-meth-
ester fibers in chlorinated hydrocarbons [187]. oxy-5-acetoxyaniline [202] in a polar, water-
The dye can also be used, especially in combi- miscible solvent.
nation with yellow and red dyes, for dyeing
human hair [188] or bones and tusks of verte-
brates [189]. It may be useful for the preparation
of infrared-fluorescent inks [190], as sensitizer
[191], or as charge-controlling agent [192] or
photoreceptor [193] in electrophotography. It
can also be used as laser dye, e.g., in solid-state Another preparation procedure consists of the
dye lasers [194] or as dye in a mono- or multi- condensation in acetic acid of 3-hydroxydi-
layer optical recording media using fluorescent methylaniline with the azo dye obtained by cou-
light for reading [195]. As a salt with surface pling diazotized p-sulfanilic acid to 2,5-di-
active anions, e.g., dodecylbenzenesulfonate, methoxyaniline [203]. The indamine dye ob-
the dye is used in thermal transfer printing on tained by condensation of 3-methoxy-4-nitroso-
acceptor sheets containing ion exchangers dimethylaniline with 2-amino-4-hydroxytoluene
[196]. and precipitation as the chlorozincate complex
Capri Blue GON 54, C.I. 51 015 [7199-02-2] can be isolated and subsequently converted into
[197], is obtained by the action of nitrosodi- the oxazine dye 55 [204].
methylaniline hydrochloride on 3-diethylami- By mixing the dye with yellow and red low
no-1-hydroxy-4-methylbenzene. The dye is molecular mass cationic dyes, a wide palette of
commercially available as Sevron Blue NF tints having high evenness is obtained [205].
(Crompton & Knowles) for dyeing polyacrylo- Dyes have also been described that, instead of
nitrile. methoxy groups, contain methyl groups in both
nuclei [206]. The dye prepared from 4-nitroso-N,
N-diethyl-m-phenetidine and 2-amino-4-hydro-
xytoluene is obtained by condensation in alco-
holic solution in the presence of zinc powder
[207]. 2-Methyl-4-nitrosomonoethylaniline, ob-
tained by rearrangement of the corresponding
Diaminophenoxazine dyes whose amino nitrosamine in hydrochloric acid solution, af-
groups bear a cyanoethyl group have proved to fords, upon condensation with m-diethylamino-
be especially valuable for dyeing polyacryloni- phenol, a dye that colors polyacrylonitrile bright
trile. For example, the dye prepared by conden- blue [208]. By joint oxidation of p-phenylene-
sation of 3-ethylmethylamino-4-methylphenol diamine and 2-amino-4-hydroxytoluene with
and 4-nitroso-N-ethyl-N-b-cyanoethylaniline K3[Fe(CN)6] in ammonia solution, an oxazine
hydrochloride in acetic acid and hydrochloric dye is obtained that bears primary amino groups
acid dyes polyacrylonitrile a clear blue [198]. in the 3- and 6-positions [209].
Also worth mentioning are dyes prepared from N, Today the only commercially relevant prod-
N-bis(cyanoethyl)aniline [199] and from N-b-cy- uct of this series is Maxilon Blue M-G (Ciba/
anoethyl-N-benzylaniline [200] according to the Huntsman). Similar products were Remacryl
same procedure. Blue B [51716-95-1], G (Hoechst), Remacryl
Vol. 4 Azine Dyes 495

Dark Blue E-GRL [64071-90-5] (Hoechst), and A commercial product of this series is Kaya-
Maxilon Blue M-2G (Ciba/Huntsman). cryl Light Blue 4GSL [12221-43-1] (Nippon
Oxazine dyes with cyclically bonded amino Kayaku).
groups are suitable for dyeing polyacrylonitrile Nile Blue A 58, C.I. 51 180 [2381-85-3]
[210]. The dye 56 imparts a bright blue color to (BASF, 1888), is prepared by reaction of 4-
these fibers. It can also be used to dye hair [211]. nitroso-3-hydroxydiethylaniline with a-naph-
thylamine [224]. The dye is used in microscopy,
immunoassays [225], and in laser technology
[226]. It is also suitable for the prevention of
deposits during the polymerization of vinyl
chloride homo-, co-, and graft polymers
[227].
Oxazine dyes with both amino groups incor-
porated in rings are used as laser dyes because of
their rigid molecular skeleton [212]. Derivatives
with sulfoalkyl groups on the ring nitrogen atom
are also known [213].
Furthermore, triaminooxazine dyes are
known that bear amino groups in the 2-, 3-, and
6-positions [214]. Their leuco products can be Nile Blue BX is the ethyl homologue of this
acylated to a ring-closed derivative suitable for dye.
electrochromic recording materials [215]. Diaminophenoxazine dyes, above all of those
Diaminophenoxazine dyes 57 in which one with a naphthalene ring system, are also obtained
amino group is substituted by a phenyl group, and by reaction of monoamino dyes, in particular
which are prepared from the correspondingly Fast New Blue 3R, with aliphatic or aromatic
substituted diphenylamino derivatives, impart to amines.
polyacrylonitrile tints having low brightness but Thus, New Methylene Blue GG 59, C.
increased lightfastness [216]. I. 51 195 [62770-30-3] (Casella, 1890), is
formed by oxidation of the product obtained by
condensation of Fast New Blue 3R 52 and di-
methylamine:

The dyes are suitable for transfer printing on

polyacrylonitrile [217]. Their tetrafluoroborates
can be used for the spin dyeing of the same
fibrous material [218]. The action of alkalis on
57 produces a color base that can be used for spin
dyeing [42] or transfer printing on textile mate- By condensation of 4-nitrosodimethylaniline
rial dyeable with cationic dyes, e.g., polyacrylo- hydrochloride with 3-hydroxydiphenylamine in
nitrile [219], and on paper coated with an acidic a molar ratio of 2:1, a basic dye is obtained that
layer [220]; the protonated dye is restored on the contains both structural features of an oxazine
material. The color base can also be alkylated on and a phenazine dye, but not of a bisazine dye
the nitrogen atom by the action of dimethyl (see Chap. 5) [228]. It dyes tannin-mordanted
sulfate or ethylene oxide [221]. The same dye cotton black.
is obtained by starting from N-alkylated diphe-
nylamino compounds [222]. Substituents in the
ortho positions of the phenyl group, in particular
methyl groups, improve the clearness of the
phenylaminooxazine dyes, because the sadden-
ing effect of the phenyl group is reduced by steric
hindrance [223].
496 Azine Dyes Vol. 4

3.3. Aminohydroxyphenoxazine Dyes under suction until the product is well dried, and
the product is further dried at 70  C. Yield: 95 %.
Aminohydroxyphenoxazine dyes largely have The ethanol is recovered by distillation.
the phenoxazone structure (1c, where D2 is ¼O). The tetraphenylborates of dyes like 61 are
Hydroxy- and aminophenoxazones exhibit char- recommended for use in electrophotographic
acteristic key bands between 6.0 and 6.5 mm in toners [235].
the IR spectrum [229]. In nature, they are present Gallo Blue E, Prune Pure, C.I. 51 040 [6416-
as orceine dyes in lichens [230]. Aminophenox- 51-9] (Sandoz, 1887), is obtained by condensa-
azone dyes are suitable for dyeing textile material tion of methyl gallate with the hydrochloride of
made from polypropylene [231]. nitrosodimethylaniline. The leuco compounds of
By the introduction of another hydroxy group these dyes were commercially available for some
in the position neighboring the OH group that time as Mordant Violets; to improve their solu-
functions as an auxochrome, the dyes acquire the bility, the dyes were also prepared as hydrogen
ability to form color lakes with chromium salts. sulfite compounds.
They can be made from derivatives of gallic acid Delphin Blue 62, C.I. 51 120 [1323-96-2],
and nitrosodialkylaniline salts and are therefore Ultracyanol B (Sandoz) is synthesized by blow-
known as gallocyanines. Gallocyanine dyes are ing air through a hot mixture of gallocyanine
used as chrome dyes on wool and cotton. Their hydrochloride and aniline, whereby the carboxyl
industrial importance has decreased; however, group is exchanged by aniline, followed by sul-
they have been recommended for the dyeing fonation and conversion to the ammonium salt.
of polyolefins in the presence of heavy-metal
salts [232].
Gallocyanine, Brilliant Chrome Blue P, C.
I. 51 030 [1562-85-2] (Sandoz, 1881), is pre-
pared by the action of 4-nitrosodimethylaniline
hydrochloride on gallic acid in methanol [233].
Coelestin Blue B 61, C.I. 51 050 [1562-90-9]
(Sandoz, Durand, Huguenin & Co., 1893), is
correspondingly obtained by action of 4-nitroso-
diethylaniline hydrochloride with gallamide Chromazurin 63, C.I. 51 125 [1323-97-3],
[234]. Chromazol Blue 5G (ICI) is synthesized analo-
gously but in the cold. Under these conditions the
aniline group bonds to the position neighboring
the carboxyl group, which is removed by subse-
quently heating to 100  C.

Preparation. In an enameled 6000 L kettle

equipped with a wooden gate stirrer, 110 kg of
gallamide and 2000 L of alcohol (denatured,
94 %) are brought to a rapid boil. Over 10 h,
240 kg of nitrosodiethylaniline hydrochloride,
dissolved in 1500 L of ethanol, is allowed to By heating Nile Blue A 58, the phenoxazone
flow in. After addition of 21 kg of potassium dye Nile Red 64, is obtained. It is used as a laser
carbonate, the reaction mixture is boiled for dye in the near-infrared (702 nm) [236]. Perfluor-
another 1 h and allowed to cool to 20  C; 40 L oalkyl groups can be introduced into dyes like 64
of 20 % hydrochloric acid is added, and the in ortho position to the oxo group by reaction
mixture is pressed into a suction filter with a with bis(perfluoroalkylcarbonyl) peroxides
filtering stone bottom. After stirring with 500 L [237]; e.g., with bis(trifluoroacetyl) peroxide a
of 20 % hydrochloric acid, the mixture is filtered trifluoromethyl-substituted dye is obtained.
Vol. 4 Azine Dyes 497

These dyes have increased stability and lightfast- reduced and converted to the sulfur dye Immedial
ness. Dyes of this type can also be used as red Blue 5R [1327-96-4] by polysulfide melt [241].
fluorescent dyes in inks, fluorescent labeling The dihydroxyphenoxazine dye resorufine
agents, fluorescent collectors, and sensors serves as a chromogenic group for the analytical
[238]. The dyes also find application in organic determination of a bacterial endotoxin [242].
light-emitting diodes (OLED’s), which are the Resorufin derivatives are used in diagnostics
basis of emissive devices showing advantageous [243] and immunoassays [244].
properties like higher brightness and lower ener-
gy consumption as compared with reflective
devices such as liquid-crystal displays [239]. 4. Thiazine Dyes
With Nile Blue as red dopant in combination
with green and blue ones, preferably in different The thiazine dyes are of minor importance today
layers, OLED’s emitting white light can be con- in the textile field because of their inferior
structed. fastness.
Silicon-containing diaminophenothiazine
dyes, which can be prepared from N,N-dimeth-
yl-p-phenylenediamine, N-(trimethylsilylpro-
pyl)aniline, and thiosulfate by oxidation with
alkali metal dichromate, are recommended for
the dyeing of glass fibers [245].
Aminohydroxyphenothiazine dyes are pres-
ent in the phenazone form (1c, where D2 is ¼S). If
3.4. Mono- and they contain a second hydroxy group in the
Dihydroxyphenoxazine Dyes position ortho to the auxochromic OH group,
they have mordant-dyeing properties.
Mono- and dihydroxyphenoxazine dyes occur in Sulfur dyes that are prepared by fusion of 4-
nature as orceine dyes [230]. Their use as food amino- and 4-nitrophenols with sulfur and sodi-
dyes is no longer allowed. The dyes are synthe- um sulfide contain a thiazine ring system, which
sized by reaction of nitrosophenols or nitroso- is, however, not in the form of the mesomeric
naphthols with phenols or naphthols. Another azine system.
route is the reaction of 1,2-naphthoquinone-4- The thiazine dyes are used for dyeing paper
sulfonic acid with 1-amino-2-naphthol-6-sulfon- and office supplies and also for the preparation of
ic acid. Alizarin Green G 65, C.I. 51 405 color lakes. The most important is Methylene
[6492-63-3], is thus obtained. It dyes chrome- Blue. In addition, the thiazine dyes have impor-
mordanted wool a bluish-tinged green. tant photochemical applications. They are used
as sensitizers in photopolymerization [246].
They are a component of a silver-free direct-
positive color bleaching-out system, because
they are reduced by the action of light and thereby
bleach out the indigoid dyes also present [247]. A
photochromic material consists of a polymer
matrix, e.g., poly(vinyl acetate), a leuco pheno-
thiazine dye, and a reducing agent. The dye is
reoxidized on irradiation [248]. If the thiazine
dye is bonded to a polymer chain, photo- and
thermochromic polymers are obtained. The dye
can be bonded to the polymer via acrylamide
[249], chloromethylstyrene [250], or vinylpyri-
dine [251]. Thiazine dyes inhibit the formation of
polymer deposits in the preparation of vinyl
1,3,4-Trichloro-7-nitrophenoxazone-2 (66) chloride homo-, co-, and graft polymers [252].
[240] is a starting material for sulfur dyes. It is Methylene Blue and other phenothiazine dyes are
498 Azine Dyes Vol. 4

used as photoreducible dyes in galvanic cells and 183 kg of sulfuric acid (78 %) are placed in a
[253]. They are also used in the leuco form as 4000 L brick-lined kettle equipped with a wood-
oxygen detectors for the detection of the unde- en stirrer, and the mixture is diluted with ice
sired admission of air, e.g., in vacuum-packed water to a volume of 1600 L. Then, 215 kg of
foodstuffs [254]. Dissolved oxygen can be re- 40 % sodium nitrite solution, together with
moved from alkaline water by treatment with 260 L of 25 % common salt solution, is allowed
leuco methylene blue [255]. Leuco dyes can also to flow in over 6 h at a temperature no higher than
be used as anodic electrochromic materials in 0  C. The mixture is subsequently stirred for 1 h
electrochromic devices such as rearview mirrors, and an additional 131 L of 78 % sulfuric acid is
sun roofs, or windows [167]. added. For the reduction, the charge is placed in a
The thiazine dyes have long been used for 2000 L kettle equipped with a heating jacket and
staining in medicine, bacteriology, and micros- treated at 25 – 40  C with 1300 kg of iron filings
copy [256]. Besides Methylene Blue and its added in 4 – 5 portions. After filtration, the
oxidation products Azur I and II, mixtures con- solution is placed in a wooden vat having a
taining these dyes can be considered for micro- capacity of 16 000 L.
scopic investigations of cells, e.g., the mixture For the oxidation to the quinonediiminothio-
Methylene Blue – Eosin [257] or the mixture of sulfonic acid, the solution is first cooled to
1  C
Azur I or Azur II with Malachite Green and and then 122 kg of 78 % sulfuric acid, diluted to
Fuchsin [258]. 600 L with water, is added in four portions over
Thiazine dyes with a naphthalene ring system 50 min as well as 120 kg of sodium dichromate
[259] are suitable for the differentiation of tissues dissolved in water (800 L solution) and 660 kg of
in surgery and pathology, since they stain malig- 45 % sodium thiosulfate solution. The final tem-
nant tissue more strongly than normal tissue. For perature should be þ1  C. Then the mixture is
the diagnosis of cell samples by staining, radio- stirred for 1 h and the temperature allowed to rise
active tritium-labeled Methylene Blue can be to 3  C. For the conversion to the indamine,
used [260]. Thiazine dyes whose amino groups 700 L of an aqueous solution containing 255 kg
are replaced by haloalkyl groups have antimitotic of sodium dichromate is added at 3 – 4  C,
activity [261]. followed by 130 kg of dimethylaniline dissolved
in 125 kg of 78 % sulfuric acid and 200 L of
water. After 30 min, 68 kg of sodium dichro-
4.1. Diaminophenothiazine Dyes mate, dissolved in 200 L of water and ice, is
added again. Finally, the mixture is stirred for
The reaction sequence that leads to the diamino- 45 min.
phenothiazine dyes is described in Chapter 1. The For the thiazine-ring cyclization, the reaction
most important dye, Methylene Blue 67, C. mixture is placed in a wooden vat having a
I. 52 015 [61-73-4], is obtained by oxidation of capacity of 26 m3. Then, 36 kg of sodium di-
4-aminodimethylaniline in the presence of sodi- chromate, dissolved in 24 L of water, and 18 kg
um thiosulfate to give the quinonediiminothio- of copper sulfate, dissolved in 100 L of water,
sulfonic acid, reaction with dimethylaniline, ox- are added, and the mixture is heated over 30 min
idation to the indamine, and cyclization to give to 90 – 92  C by blowing in steam. Dye forma-
the thiazine. The dye is commercially available tion starts between 65 and 70  C. Finally, the
as the hydrochloride and as the zinc chloride mixture is stirred for another 30 min at 90 –
double salt. 92  C, and the chromium sediment is then
filtered off.
To prepare the zinc chloride double salt, the
solution is treated at 45  C with 40 L of 30 %
hydrochloric acid, 300 L of 40 % zinc chloride
solution, and 1000 kg of common salt solution,
saturated at 45  C. The mixture is allowed to cool
to 20  C and the product is filtered off and dried
Preparation. To prepare the nitroso com- at 60 – 65  C in a circulating-air dryer. Yield:
pound, 150 kg of dimethylaniline, 750 kg of ice, 375 kg.
Vol. 4 Azine Dyes 499

To isolate Methylene Blue hydrochloride, the crude product with toluene [269].
40 L of 30 % hydrochloric acid and 2000 kg of
saturated common salt solution are added to the
dye solution after it has cooled to 45  C, and the
mixture is allowed to cool further to 25  C. After
filtration, the product is washed with a 2 %
common salt solution.
Instead of sodium dichromate, manganese
dioxide and catalytic amounts of copper sulfate
can be used for the oxidation [262]. Finally
another procedure for the preparation of pheno- In place of the benzoyl group, the residues of
thiazine dyes has been reported in which the halobenzoic acids [270], nitrobenzoic acids
reaction is carried out with sodium thiosulfate [271], aminobenzoic acids [272], sulfobenzoic
in the presence of zinc chloride and aluminum acids [273], benzenedicarboxylic acids [274],
sulfate, and the oxidation is carried out with naphthalenecarboxylic acids [275], isobutyric
sodium dichromate in the presence of copper acid [276], as well as alkyl- and arylsulfonic
sulfate in sulfuric acid [263]. acids [277] have been suggested. Reaction pro-
Highly pure Methylene Blue can be obtained ducts with esters of chloroformic acid and iso-
by extraction of impurities with chloroform from cyanates [278] can also be used. The lightfastness
solutions of raw dye in borate puffer at pH 9.5 – of the printing is improved by heteropolyacids of
10 followed by acidification of the aqueous hexavalent molybdenum, such as phosphomo-
solution and isolation of the dye [264]. lybdic acid [279].
Methylene Blue is mainly used to dye paper Benzoylleucomethylene blue was used as a
and office supplies, but also to tone up silk colors. color-forming agent in colorless copying paper
In addition, it is of some importance as a che- [280]. It is also recommended for documents to
motherapeutic agent in human and animal medi- make them safe against forgery [281].
cine, as a stain in microscopy, as a hydrogen On contact with acid substances, such as
acceptor in enzymatic dehydrogenations, as a attapulgite, montmorillonite, kaolinite, or ben-
redox indicator in iodometry and titanometry, tonite, the color of Methylene Blue is slowly
and as a cosmetic dye. In combination with developed. The compound is also used as color-
illumination the dye or its homologues can be forming agent in thermoreactive paper in com-
used to promote wound healing of chronic ulcers bination with aromatic hydroxy compounds serv-
[265]. ing as acidic substances in this case. The color
Methylene Blue was offered as Leather Pure reaction is effected by the action of heat, which
Blue HB [61-73-4] (Hoechst) for dyeing leather causes the melting of the covering poly(vinyl
and is a mixture component in Basic Leather alcohol) [282].
Black brands. It can be adsorbed by active char- The mechanism of color-forming decomposi-
coal and then be used to remove BF4
anions tion of N-benzoylleucomethylene blue during the
from wastewater [266]. copying process has been studied; the reaction is
Methylene Blue has also been investigated as induced by photons and proceeds via free radi-
a dye in laser technology [41] and as an IR cals [283].
sensitizer generating 1O2 useful in holographic Benzoylleucomethylene blue was also used in
registration material using the polymerization of combination with other chromogenic com-
acrylic monomers [267]. It sensibilizes the pho- pounds, e.g., with Crystal Violet lactone [284],
tochemical degradation of azo dyes with 1O2 rhodamineanilinolactam [285], spiro compounds
[268]. It is used as antidote against methemoglo- [286], and fluoranes [287]. Its slow development
bin-forming poisons and as disinfectant in animal compensates the bleaching of color formers with
medicine. low lightfastness, e.g., Crystal Violet lactone. N-
10-Benzoylleucomethylene Blue [1249-97-4] Alkyl- or arylsulfonylleucomethylene blue can
68 is obtained by reduction of Methylene Blue be used in a dye sublimation sheet which uses
with hydrosulfite in aqueous alkaline medium, nickel salicylates as developing agent on the
followed by benzoylation and then extraction of receiver sheet [288].
500 Azine Dyes Vol. 4

A commercial product of this series was React Methylene Green 70, C.I. 52 020 [6722-15-2]
Blue G (BASF). (MLB, 1886), is obtained by action of nitric acid
Recording materials for electron beams con- on Methylene Blue.
tain benzoyl- or naphthoylleucomethylene blue
in order to increase the sensitivity [289]. Elec-
trochromic printing media contain N-benzoyl-
leucomethylene blue and a bromide, which cat-
alyzes the electrochemical oxidation of the leuco
compound [273, 290]. Benzoyl leuco derivatives Several dyes that are important in microscopy
of Azur I bearing an additional benzoyl group on are obtained by partial oxidative degradation of
the methylamino group can also be used in the Methylene Blue, which removes some of the
same manner [291]. N-Acylated leucophenothia- methyl groups. Cleavage of one methyl group
zine compounds also serve to stabilize polymeric gives Azur I (Azur B), of two methyl groups Azur
hydrocarbons [292] and polychloroprenes [293]. A, and of three methyl groups Azur C. The
Leucomethylene blue is used in oxygen de- oxidation is favorably carried out in an aqueous
tectors checking, e.g., nitrogen-blanketed or vac- solution of potassium or sodium dichromate at
uum-packed perishable foodstuffs [294]. It is 70  C [303]. Highly purified rhodanides of these
also recommended as oxygen-sensitive reactive dyes can be made starting from the zinc chloride
material in optical data storage media such as salts via the perchlorates [304]. Another dye for
CDs and DVDs which are intended to be usable this purpose is Thionine or Lauth’s Violet, C.
(readable) only for a limited period of time [295]. I. 52 000 [581-64-6], with completely unsubsti-
The halogenation of Methylene Blue im- tuted amino groups. A rapid method for separa-
proves the lightfastness of the color on polyac- tion and identification of these dyes is high-
rylonitrile [296]. The selenium analogue of performance thin-layer chromatography [305].
Methylene Blue, prepared with 75Se, is used for Thiocarmin R [6379-04-0] (71; Cassella,
the imaging of epithelial corpuscle adomenas 1890), is an acid wool dye from the series of
[297]. Inclusion complexation of Methylene diaminophenothiazine dyes [306]. It has been
Blue in b-cyclodextrin enhances the lightfastness prepared, analogously to Lauth’s Violet, by oxi-
even on textile fibers [298] and the fluorescence dation of 4-amino-N-ethyl-N-benzylaniline-30 -
intensity by a factor of 3 – 5 [299]. sulfonic acid in the presence of hydrogen sulfide
Derivatives of Methylene Blue bearing, in- and zinc chloride. In this case, too, better yields
stead of one methyl group, a substituent which are obtained by using the thiosulfate method (see
can react with amino, thiol, or carboxyl groups the discussion under Methylene Blue). According
are applicable to photodynamic therapy of cancer to the same preparation route, the thioninedisul-
or immunoassays utilizing chemoluminescence fonic acid is obtained from 2,5-diaminobenzene-
[300]. sulfonic acid and 2-aminobenzenesulfonic acid.
Methylene Blue NNX, New Methylene Blue, C.
I. 52 030 [6586-05-6] (Cassella, 1881), is redder
and somewhat faster to light than Methylene
Blue [301]. It can be prepared analogously to
Methylene Blue, starting from N-ethyl-2,5-dia-
minotoluene and N-ethyl-o-toluidine, and is suit-
able as a stain for microscopy. This dye [307] as well as cationic phenothia-
Toluidine Blue O 69, C.I. 52 040 [6586-04-5] zine dyes can be used in photogalvanic cells
(MLB, BASF, 1888), is prepared from N,N-di- [308].
methyl-p-phenylenediamine and o-toluidine and
is used as a stain for microscopy [302].
4.2. Aminohydroxyphenothiazine
Dyes

These dyes are essentially completely present in

the phenazone form (1c, where D2 is ¼O). They
Vol. 4 Azine Dyes 501

are suitable for dyeing polypropylene textile 4.3. Hydroxyphenothiazine Dyes

materials [309]. By the introduction of a second
hydroxy group in the position neighboring the Hydroxyphenothiazine dyes serve as starting
auxochromic OH group, the dyes acquire the material for sulfur dyes. 1,3,4-Trichloro-7-
ability to form color lakes. methylphenothiazine-2-one, obtained from
Brilliant Alizarin Blue G 72 and R 73, C. chloranil and 1-methyl-4-amino-3-thiophenol, is
I. 52 055 [6379-01-7] and C.I. 52 060 [6379- the precursor for the former Immedial Reddish
02-8], dye chrome-mordanted wool green-tinged Brown CL3R.
and red-tinged blue, respectively. The dyes are
obtained by reaction of the corresponding phe-
nylenediaminothiosulfonic acids with 1,2- 5. Bisazine Dyes
naphthoquinone-4-sulfonic acid and -4,6-disul-
fonic acid, respectively (Bayer, 1892) [310]. By doubling of the general formula 1 of the azine
dyes, one arrives at the general formula 76 of the
bisazine dyes.

Whereas an uneven number of carbon atoms

and heteroatoms is found between the two aux-
ochrome groups D1 and D2 in the simple azine
dyes, so that resonance formulas 1a – 1c are
possible, the D groups in the bisazine dyes are
separated by an even number of atoms, and
therefore resonance in the sense of formula 1 is
impossible.
By reaction of 1,4-naphthoquinone with thio- The color of the bisazine dyes results from
urea, cyclic thiocarbonate 74 is obtained, which coupling of two trimethine chromophores ac-
can be treated with nitrosodiethylaniline to give cording to 77, which is a kind of a 1,4-didonor
thiophenoxazone dye 75. The dye is also formed 2,5-diacceptor substituted benzene 78. The mix-
in a chromogenic developing process on image- ing of their highest occupied and lowest unoccu-
forming irradiation of dialkyl-p-phenylenedia- pied molecular orbitals, respectively, yields a
mine in a silver-halide-containing gelatin significant bathochromic shift of the absorption
layer [311]. band [313]. This shift and the color strength are
increased by the condensed rings. Therefore, the
groups D are not necessarily required and are
lacking in a large number of important dyes.

As a laser dye, it is tunable in the 660 – 700 The bisazine dyes include the fluorindine
nm range [312]. dyes, the dioxazine dyes, and the dithiazine dyes.
502 Azine Dyes Vol. 4

Of these, the dioxazine dyes have the greatest by reaction of benzoquinone derivatives, in
industrial importance. particular tetrachlorobenzoquinone (chloranil),
with aromatic amines. The components are
first condensed in the presence of acid-binding
5.1. Fluorindine Dyes agents to give 2,5-diarylamino-3,6-dichloro-
1,4-benzoquinone. The cyclization is then
Fluorindine dyes are obtained by reaction of carried out under oxidative conditions in
benzoquinone derivatives with phenylenedia- high-boiling solvents in the presence of aromat-
mine. 5,12-Dialkylfluorindines can be prepared ic acid chlorides or in concentrated sulfuric
by first adding two equivalents of N-alkyl-o- acid [321]:
phenylenediamine to benzoquinone in the cold
and then heating in acidic medium to form
the azine ring [314]. The compounds are also
obtained by condensing 2,5-dihydroxybenzo-
quinone with N-alkyl-o-phenylenediamines in
pyridine at reflux temperature. The dyes are
suitable for polyacrylonitrile [315]. They are
quaternized by the action of alkylating agents to
dyes like 79, thereby becoming more soluble
and electronically more similar to monoamino-
phenazine dyes. Polyacrylonitrile is dyed in
blue tints [316].

The alkylated diphenylfluorindines are also

suitable for dyeing polyacrylonitrile [317]. In- Instead of the widely used o-dichlorobenzene
teresting derivatives of diphenylfluorindine are aryl alkyl ethers are recommended as halogen-
described in [318]. They are formed when 3- free solvents [322].
aminopyrenes are incorporated into azophenine Several modifications of the cyclization
compounds, and these are converted into fluor- step allow the reaction to be run under milder
indines and made water-soluble by sulfonation. conditions, even at room temperature: oleum
The products of high color strength dye cotton [323], manganese dioxide in sulfuric acid
from a neutral bath in lightfast green tints. [324], chlorine in oleum [325], iodine or an
Fluorindine dyes that contain sulfo groups are inorganic [326] or organic [327] iodine compound
obtained by reaction of o-phenylenediamine- in oleum, bis(acetoxyiodo)benzene [328], per-
mono- or o-phenylenediaminedisulfonic acids borate or percarbonate in sulfuric acid or oleum
with 2,5-dimethoxy-1,4-benzoquinone [319]. A [329], electrochemical oxidation [330].
violet pigment can be prepared by treating If the aromatic rings A and B do not contain,
monobenzoyl-o-phenylenediamine with chlor- e.g., a sulfo group compounds 80 are water-
anil, followed by condensation to give the fluor- insoluble and have pigment character. Of special
indine [320]. importance is Pigment Violet 23 81, C.I. 51 319
[6358-30-1], formed by condensation of chlor-
anil with 3-amino-N-ethylcarbazole. Linear
5.2. Dioxazine Dyes structure 81a was believed for long time to be
the right one. But three-dimensional X-ray dif-
This class of dyes, which is especially important fraction analysis revealed the angled structure
in dyeing cotton and as pigments, is prepared 81 [331].
Vol. 4 Azine Dyes 503

mended for use in electrophotography [335], in

organic electroluminescence devices [336], for
optical data storage [337], or as shading agent
together with copper phthalocyanine as light
filter in liquid crystal displays [338]. To convert
the crude dye to a clear, color-strength pigment,
the aqueous suspension is heated in the presence
of an aliphatic or alicyclic alcohol [339], an
aromatic hydrocarbon [340], a ketone, or an
acetic ester [341]. The pigment can be dispersed
by dissolving it in a haloacetic acid and diluting it
with water or a water-miscible solvent [342].
Dispersion can also be achieved by grinding in
a vibrator mill [343]. The dispersibility of the
pigment can be improved by mixing it with a
derivative of this pigment bearing amino or
heterocyclic groups bound to the chromophore
Linear structure 81a is said to exhibit a blue
by spacer groups such as methylene or sulfonyl
shade and very poor application properties com-
[344]. Mixtures with derivatives obtained
pared with the angled structure 81.
by reaction of Pigment Violet 23 with chloro-
Starting from 3-amino-2-methoxycarbazoles
sulfonic acid followed by reaction with dimethy-
dioxazines having a linear 81a or angular 82
laminopropyleneamine result in paint or ink
structure seem to be obtainable depending from
dispersions with low viscosity and high
the conditions used for the ring closing step,
gloss [345].
whereby the methoxy groups are split off
Pigment Violet 23 as tailor-made preparations
(!81a) or retained in the molecule (!82)
for different applications is commercially avail-
[332]. With such carbazoles bearing a long-chain
able in a great variety of assortments, e.g., Hos-
alkyl group on the nitrogen atom, soluble carba-
taperm Violet BL, Hostatint Violet RL, Colanyl
zoledioxazine dyes have been synthesized by
Violet RL 200 (Clariant), Paliogen Violet L 5890,
condensation with chloranil and ring closure in
Xfast Violet ED 7575 (BASF), Pigment Violet 23
1-chloronaphthaline at 220  C. The linear struc-
(Sun-Chemicals).
ture (analogous to 81a) of the molecule has been
The halogen-free pigment is also known. It is
confirmed by 1H NMR spectroscopy and X-ray
synthesized from p-benzoquinone and 3-amino-
crystallography [333]. Such long-chain substi-
N-alkylcarbazoles under oxidative conditions
tuted dyes are recommended as colorants in
[346] or from 2,5-dihalo- [347] or 2,5-dihy-
resins, inks, and for photoelectric materials
droxy-1,4-benzoquinone [348]. The monochloro
[334].
pigment is analogously obtained from 2,3,5-tri-
chloro-1,4-benzoquinone [349].
Water-soluble dyes are formed by sulfona-
tion. They dye cotton directly in vivid violet and
blue tints and are characterized by high lightfast-
ness and high color strength. Because animal
fibers are also deeply colored, the sulfonated
dioxazine dyes are suitable in mixture with acid
wool dyes for the dyeing of half-wool. These
industrially important dyes are derived from 4-
aminodiphenylamine or from multinuclear aro-
The preparation of Pigment Violet 23 is de- matic amines.
scribed below. The pigment serves for the dyeing Sirius Light Blue FFRL, or Remastral Blue
of plastics, such as PVC, polyolefins, polysty- FFRRL, C.I. 51 320 [1324-58-9], is prepared by
rene, and rubber, as well for the preparation of condensation of chloranil and 3-amino-N-ethyl-
printing colors and paints. It is also recom- carbazole followed by sulfonation [321].
504 Azine Dyes Vol. 4

Preparation. N-oxide are advantageous because they produce

less wastewater than arenesulfonyl chlorides, but
1. Condensation and oxazine-ring cyclization. high yields of pigments [353].
In a 2000 L enameled kettle equipped with The unsulfonated color bases can be treated
heater, stirrer, and condenser, 100 kg of 3- with N-hydroxymethylchloroacetamide to add
amino-N-ethylcarbazole, 42.5 kg of water- one to four amidomethyl groups to the dye
free sodium acetate, and 87.5 kg of chloranil molecule. With pyridine, the chlorine substituent
are mixed by stirring in 1940 kg of o-dichlo- is exchanged for the pyridinium group to give
robenzene at 50 – 55  C. The mixture is stir- cationic dyes that are suitable for spin dyeing of
red for 2 h at 60 – 68  C, and the acetic acid is polyacrylonitrile [354]. By the action of oleum
then distilled under vacuum at 115  C. Sub- on these dyes, compounds are formed that bear
sequently, 45 kg of benzenesulfonyl chloride cationic charges as well as sulfo groups and are
is added at 150  C, and the solution is heated suitable for dyeing natural and synthetic fibers as
to 175 – 180  C, stirred for 4 h at this tem- well as paper and leather [355]. The chloroacetyl
perature, allowed to cool, diluted with o-di- group can also be cleaved off with hydrochloric
chlorobenzene, and filtered at 100  C through acid and the aminomethylated dye can be treated
a pressure filter. The filter residue is washed with the reaction product formed from cyanuric
with o-dichlorobenzene at 100  C until a fluoride and o-sulfanilic acid. The dye thus ob-
sample amount, boiled in o-dichlorobenzene, tained reacts with natural and regenerated cellu-
fluoresces red rather than blue. The o-dichlo- lose with formation of a covalent bond [356].
robenzene is then removed by steam distilla- Sirius Light Blue FF2GL, or Remastral Blue
tion and the product is washed with hot water FF2GL 83, C.I. 51 300 [6527-70-4], is prepared
and dried at 100  C. from chloranil and 4-aminodiphenylamine-2-
2. Sulfonation. 85 kg of ground dioxazine inter- sulfonic acid [357].
mediate is added through a sieve over 2 h at
room temperature to a mixture containing
1050 kg of 95.5 % sulfuric acid and 1050 kg
of fuming sulfuric acid (29 % SO3). The
mixture is heated to 90 – 95  C over 1 h and
stirred for 8 h at this temperature. It is then
allowed to cool to 25 – 30  C. 1000 kg of
water and 2000 kg of ice are added, the
mixture is stirred for 24 h and filtered, and
the product is washed with a 17 % solution of
NaCl. The sulfonated product is mixed with Other trade names were Solophenyl Brilliant
1000 kg of a 23 % solution of NaCl and made Blue BL, Chlorantin Fast Brilliant Blue 2 GL
weakly alkaline with a solution of soda. After (Ciba-Geigy), Tertro Direct Light Blue 2GLN
2 h of stirring, the sodium salt is salted out (Crompton & Knowles).
with 100 kg of NaCl, filtered, and washed The corresponding dye obtained from 4-
with 1500 L of a 23 % NaCl solution until amino-40 -chlorodiphenylamine-2-sulfonic acid
the filtrate flows out with a weak blue color. is Sirius Light Blue FFB. These dyes are also
The salt is dried at 60 – 70  C. suitable for the batch dyeing of polyamides
[358].
The reaction of chloranil with 3-amino-N- The reaction of chloranil with 1,4-phenylene-
ethylcarbazole is favorably carried out in the diamine-2-sulfonic acid gives, after cyclization,
presence of a phase-transfer catalyst, e.g., tetra- a dioxazine dye with primary amino groups
butylammonium chloride [350]. Organic bases which dyes polyamide a clear blue [359]. By
such as triethylamine, piperazine, and pyridine reaction with cyanuric chloride, it is converted to
have also been suggested as acid-binding agents a reactive dye [360]. Introduction of substituted
[351]. Benzenesulfonic acid and toluenesulfonic amino groups into the triazine rings gives
acid are also suitable as condensation agents dyes useful as direct dyes for textile fibers,
[352]. Heterocyclic N-oxides such as 4-picoline leather, paper, and in ink-jet inks [361]. Two
Vol. 4 Azine Dyes 505

chromophores of this dioxazine dye can be com- excellent durability especially to heat and under
bined by a bridging group formed by reaction moist, hot conditions [368].
with, e.g., phosgene or dicarboxylic acid dichlor- Asymmetrical dioxazine dyes can be synthe-
ides [362] or cyanuric chloride [363]. These dyes sized by subsequent condensation of chloranil
give a brilliant lightfast blue tint on cellulosic with p-phenylenesulfonic acid and p-phenylene-
material such as cotton and paper. They are also 2,6-disulfonic acid followed by ring closure.
recommended as dichroitic dyes in light-polariz- Reaction with cyanuric chloride and substitution
ing films [364]. of the remaining two chlorine atoms by metanilic
A sulfone residue can be introduced into these acid and 2-(20 -hydroxyethylsulfonyl)ethylamine
dyes in ortho position to one of the amino groups yields a reddish blue dye, which after esterifica-
by reaction with sulfinic acids, e.g., acetamido- tion of the free hydroxy group by 100 % sulfuric
benzenesulfinic acid, in the presence of an oxi- acid becomes a reactive dye, especially for cel-
dizing agent, e.g., potassium peroxodisulfate lulose fiber materials [369].
[365]. These dyes provide brilliant reddish blue
shades on polyamide and wool.
Another starting material for the preparation
of dioxazine reactive dyes is the product obtained
from the reaction of 4,40 -diaminodiphenylamine
disulfonic acid with chloranil. The primary ami-
no groups react with cyanuric chloride to form 84
[366].

Another reactive group can be introduced into Dioxazine dyes that bear an aminoalkylamino
this dye by allowing the second chlorine atom of group are starting materials for the preparation of
cyanuric chloride to react with the sulfate ester of reactive dyes such as 86. The aliphatic amino
3-aminophenylhydroxyethylsulfone [367]. group is reacted with cyanuric chloride [370] or
Commercial products of this series were Procion with cyanuric fluoride [371], a second halogen
Blue MX-G [72847-56-4] (ICI), Intracron Blue atom on the triazine ring usually being ex-
C-G (Crompton & Knowles). changed for an anilinesulfonic acid. Higher bril-
Dyes of this type in which rodlike substituents liance, a less reddish blue shade, and a higher
are fixed to the amino groups can be used as stability to alkali are said to be the advantages of
dichroitic dyes in polarizing films. They show these chromophores.
506 Azine Dyes Vol. 4

Substitution of the third halogen atom by an phenol, and 4-ethoxyaniline-3-sulfonic acid

amine [372] or by nicotinic acid [373] results in [382].
paper dyes and reactive dyes for cotton, respec- Sirius Light Blue F3GL, or Remastral Blue
tively, which can be used under neutral to acidic F3GL 88, C.I. 51 310 [30282-46-3], is obtained
dyeing conditions [374]. Procion Blue H-EG, C. by condensation of chloranil with aminopyrene
I. 51 307 [77093-21-1] (ICI, DyStar), Kayacelon and cyclization in the presence of p-toluenesul-
React Brilliant Blue CN-FL (Nippon Kayaku) is fonyl chloride and 1-chloronaphthalene at
a commercial dye of the latter type. 260  C. Sulfonation is carried out with a 15-fold
Oligomeric dyes can be synthesized by reac- excess of sulfuric acid monohydrate at 20  C for
tion of these aminoalkylamino groups with bi- 36 – 40 h [383].
functional acid chlorides, e.g., terephthalic acid
dichloride [375]. These dyes can be used for
dyeing and printing of cellulose material.
The precursors of these dyes can be desulfo-
nated by heating in the presence of a mineral acid
and subsequently alkylated. The cationic dyes
thus obtained are suitable for dyeing paper [376].
Starting from g-[2-(b-hydroxyethylsulfonyl)-4-
aminoanilino]propyltrialkylammonium iodide, Sirius Light Violet FRL, or Remastral Violet
e.g., reaction with chloranil, ring closure, and FRL, C.I. 51 325 [1324-43-2], is obtained cor-
esterification of the hydroxy groups yields a respondingly from 2-aminofluorene [384].
cationic reactive dioxazine dye of high color If aromatic amines that bear an alkoxy group
strength which dyes cellulose, wool, or polyam- in the position neighboring the amino group are
ide in fast reddish blue hues [377]. used for the condensation, the oxazine-ring cy-
Red dioxazine dyes are obtained by conden- clization takes place with elimination of alcohol.
sation of 4-aminodiphenyl ether with chloranil, Pigment dyes are obtained by condensation of
followed by either sulfonation of the dioxazine to chloranil with 1,4-dialkoxy-2-amino-5-aroyla-
give a polyamide dye [378] or by reaction of the minobenzenes followed by ring cyclization in
dioxazine with N-hydroxymethylchloroaceta- concentrated sulfuric acid [385] with reacylation
mide and pyridine to give a cationic paper dye of saponified acylamino groups [386] or by ring
such as 87 [379]. cyclization in a solvent in the presence of sodium

Condensation of chloranil with 3-sulfo-4- sulfate [387].

(w-acylaminoalkoxy)anilines followed by hy- Commercial products of this class of dyes
drolysis of the amide and reaction with a fiber- were Irgazin Violet BLT [55177-94-1] and 6RLT
reactive group, e.g., with cyanuric fluoride and [12612-32-7] (Ciba-Geigy/Ciba Specialty
then with anilinesulfonic acid [380], or conden- Products).
sation of chloranil with 3-sulfo-4-(w-sulfa- Pigment dyes that bear acylamino groups
toethylsulfonylalkoxy)anilines [381] yields blu- instead of chlorine in the 3- and 6-positions are
ish red dyes for reactive dyeing of cellulose obtained by reaction of 2,5-dihalo-3,6-bis(acy-
material. Chlorine-free magenta dyes useful for lamino)-1,4-benzoquinone with aromatic amines
ink-jet printing are synthesized from tetraphe- bearing an alkoxy group in the position neigh-
noxybenzoquinone, obtained from chloranil and boring the amino group. Suitable acyl groups are
Vol. 4 Azine Dyes 507

the benzoyl group [388], the acetyl group [389],

and the thiophenoyl group [390]. By exchange of
the halogen atoms in the 3- and 6-positions for the
cyano group, other valuable pigment dyes can be
prepared [391]. Phenoxy groups [392], carbox-
ylic esters, or carbonamide groups [393] also The reaction of phenothiazones with o-ami-
come into consideration as substituents in the nothiophenols proceeds according to the follow-
3- and 6-positions. ing equation:
A commercial product of this series is Cro-
mophtal Violet B [57971-98-9] (Ciba Specialty
Products).
6-Sulfonyl-substituted dioxazine dyes with
alkyl or aryl groups in the 3-position are recom-
mended for dyeing paper or cotton as substantive
[394] or reactive dyes [395].
Dioxazine dyes that bear alkoxy groups
[396], polyether groups [397], or phenoxy
groups [398] as substituents are suitable for the
spin dyeing of polyesters. A color-strong, red-
dish violet vat dye is reported to be formed by
treatment of triphendioxazine with AlCl32
S2Cl2 complex [399].
Dioxazine dyes, e.g., Pigment Violet 23, are
suitable for information storage using the gallium
arsenide semiconductor laser due to their absorp-
tion between 600 and 800 nm [400].
MUSSO et al. have investigated the formation
of triphendioxazine from 2-hydroxy-p-benzo-
quinone and 2-aminophenol [401].

The diazine dyes thus obtained are sulfonated

5.3. Dithiazine Dyes at 60  C with sulfuric acid or oleum, depending
on their constitution. The sulfonic acids dye
Dithiazine dyes are suitable in their sulfonated cotton with reddish-violet to green tints.
form for the substantive dyeing of cotton [402].
To prepare the parent substances (89 or 90), two
methods can be considered: the sulfurization of
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72 W. E. Solodar, A. R. Monahan, Can. J. Chem. 54 (1976) 102 D. M. Molihner, R. N. Adams, W. J. Argersinger, Jr.,
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77 Fuji, JP 62 032 449, 1985. va, G. A. Tolkaceva).
78 Seiko Epson, EP 453 578, 1989 (H. Hayashi). 108 AS Azerb. Chloro-Org., SU 712 425, 1978 (B. A.
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80 Bayer, EP 32 240, 1980 (W. Maurer, J. Zimmer). ki, H. Maslowski, D. Jagodzinska, B. Czuprynski).
81 Taoka Dyestuff, JP 50 130 817, 1974. 110 VEB Bitterfeld, DD 93 211, 1971 (F. Kleine, W. Simon).
82 Amer. Cyanamid, DE-OS 3 018 842, 1980 111 Fuji Xerox Co., JP 61 117 566, 1984 (Y. Matsumura).
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83 Taoka Dyestuff, JP 50 148 427, 1974. H. Niimura).
84 Aziende Colori Nazionali Affini, DE-OS 2 846 803, 113 J. J. Langer, Mater. Sci. 10 (1984) 173.
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89 H. M. S. Ziena, M. M. Youssef, M. E. Aman, Food 120 Hoechst, DE-OS 2 909 034, 1979 (K. Rosenbusch).
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92 Amer. Cyanamid, US 4 321 178, 1980, (E. L. Miller). 125 Henkel, DE-OS 2 935 429, 1979 (G. Konrad, E. Lieske);
93 Whittaker, DE-OS 2 935 861, (1978) I. R. Mansukhani). DE-OS 3 016 882, 1980 (G. Konrad, D. Rose, N. Maak).
94 Perm. Chem. Works, SU 740 804, 1978 (S. N. Gusij, 126 Henkel, DE-OS 2 628 999, 1976 (D. Rose, E. Weinrich,
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98 Pentel, JP 07 118 590, 1993. 132 Henkel, DE-OS 2 706 029, 1977 (D. Rose, P. Busch, E.
99 BASF, EP 325 999, 1988 (G. Riedel, D. Hoffmann, Lieske).
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100 BASF, DE-OS 1 954 549, 1969 (A. Tartier). Boosen). Wella, DE-OS 19 619 112, 1996 (W. R.
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134 Therachemie, DE-OS 1 792 526, 1968 (R. Maul, Verlag 1973, p. 172 ff. R. Raue, H. Harnisch, K. H.
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137 Henkel, DE-OS 4 330 711, 1993 (H. Hoeffkes, E. Lieske, Sumitomo, JP 76 29 045, 1972. Fuji, JP 55 67 096, 1978.
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140 L’Or
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141 L’Or
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143 L’Or
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144 L’Or
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145 L’Or
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148 Wella, GB 2 239 265, 1991, (H. Mager, R. Rau). G. Sch€afer); JP 77 96 94, 1969.
149 Schwarzkopf, DE-OS 19 826 456, 1998 (M. Akram, 170 Miles Lab., US 3 732 147, 1970 (A. P. Fosker, P. J. Mill).
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150 M. Gago-Dominquez, J. E. Castelao, J.-M. Yuan, 172 L. K. Denisov, SU 1 141 958, 1983.
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186 Sumitomo, JP 52 37 885, 1975. 217 Nippon Kayaku, JP 51 53 086, 1974.

187 Du Pont, US 4 063 889, 1975 (E. Kissa). 218 Ciba-Geigy, EP 55 223, 1980 (P. Loew).
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DE-OS 29 912 327, 1999. P. Moser).
189 Ciba-Geigy, DE-OS 4 326 460, 1992 (U. Lehmann). 220 BASF, EP 273 307, 1986 (J. P. Dix, K.-H. Etzbach,
190 IBM, EP 85 157, 1982 (M. A. Acitelli, R. F. Tynan, U. Mayer, R. Sens).
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193 Canon, JP 63 74 068, 1986. 223 BASF, DE-OS 2 158 121, 1971 (H. Baumann,
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200 ICI, DE-OS 2 259 341, 1972 (R. Baker, J. L. Leng). 232 Ube Nitto Kasei, JP 13 596/66, 1962.
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201 Ciba-Geigy, DE-OS 25 18 587, 1974 (P. Moser, 234 Friedl€ ander, vol. 4, p. 485.
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54 70 887, 1977; DE-OS 2 812 870, 1977 (Y. Yoshi- (W. E. Bernier). Mitsubishi Electric, JP 58 38 782, 1981.
kawa, M. Goto, T. Nawata, Y. Kondo); DE-OS 3 025 291 Hilton-Davis, EP 170 188, 1984 (M. B. Gunn, W. Mo-
264, 1979 (Y. Yoshikawa, T. Nawata, M. Goto, Y. Fujii). Wei Hung).
255 Nalco Chem., US 4 311 599, 1980 (M. Slovinsky). 292 Dainichi Nippon Cables, JP 50 158 638, 1974.
256 Merck, DE-OS 3 112 442, 1981 (W. Fischer, R. Link). 293 Dainichi Nippon Cables, JP 51 47 942, 1974; JP 51 112
257 A. Dousset, FR 2 027 498, 1969. Miles Lab., US 4 392 857, 1975; JP 51 121 053, 1975.
864, 1982 (E. A. Helfrich, K. F. Yip). 294 Teijin, JP 86 043 661, 1986.
258 Spitalul de Boli Infect. Col., DE-OS 1 914 675, 1969 295 General Electric Comp., WO 03/090220, 2002
(I. C. Marinescu). (K. A. Ezbiansky, D. R. Olson, P. Schottland, V. Thomas,
259 Amer. Cyanamid, US 2 607 774, 1951 (R. C. Clapp). M. B. Wisnudel).
260 Bio-Digital Sc., DE-OS 2 341 061, 1972 (J. H. Nodine, 296 Mitsubishi, DE-OS 2 354 084, 1972 (S. Inoue, H. Honda,
H. Waite, J. H. Waite, M. J. Fletcher). F. Kitakyushu).
261 Egyes€ ult Gyógyszer
es T
apszergy
ar, BE 728 439, 1968. 297 Hoechst, EP 68 425, 1981 (G. Waschulzik,
262 Amer. Cyanamid, US 4 212 971, 1979 (F. V. Randvere, H. Oehlschl€ager, H. Schuldes).
L. M. Konzelman). 298 Mitsubishi Electr., JP 62 100 557, 1985. K. Enmanji,
263 Interpr. Chimica Dudesti, RU 63 231, 1974 (I. G. T. Andoh, Nippon Kagaku Kaishi 1987 1078.
Lukavchenko). 299 C. Lee, Y. W. Sung, J. W. Park, J. Phys. Chem. B 103
264 V. Kuban, I. Jancarova, Chem. Listy 79 (1985) 1200. (1999) 893.
265 Photopharmica Ltd., WO2006032847, 2004 (S. B. 300 Takeda Chem. Ind., EP 510 668, 1991 (H. Masuya,
Brown, C. C. Ogrady). H. Shimadzu, T. Miyawaki, M. A. Motsenbocker).
266 Hitachi, JP 55 94 680, 1979; JP 55 94 681, 1979; JP 55 301 Friedl€ander, vol. 3, p. 360.
94 682, 1979. 302 Friedl€ander, vol. 2, p. 153.
267 Etat Français, FR 2 570 517, 1984 (P. Gravey, 303 Intreprind. Chim. Dudesti, RU 63 783, 1973
J.-Y. Moisan, J.-P. Fouassier, D. Lognot). (K. A. Lobashov, E. M. Spektor).
268 Zollinger, Color Chemistry, 2nd ed., Weinheim, VCH 304 Heyl Chemisch-pharmazeutische Fabrik, DE-OS 3 305
Verlagsgesellschaft, 1991. 304, 1983 (S. Heydolph, W. Parr, E. Heyl).
269 Mita Ind., JP 52 89 131, 1976. 305 B. M. van Liedekerke, A. P. De Leenheer, B. M. De
270 National Cash Reg., DE-AS 1 065 114, 1956. Spiegeleer, J. Chromatogr. Sci., 29 (1991) 49.
271 National Cash Reg., DE-AS 1 065 546, 1956. 306 Friedl€ander, vol. 2, p. 156.
272 Yamada Kagaku, JP 56 104 094, 1980. 307 W. J. Albery, P. N. Bartlett, A. W. Foulds, F. A. Souto-
273 IBM, US 4 309 255, 1980 (P. L. Gendler, B. D. Grant, Bachiller, R. Whiteside, J. Chem. Soc. Perkin Trans. 2
C. D. Snyder). 1981, 794.
274 Sumitomo, JP 50 20 809, 1973. 308 Shell, GB 2 083 488, 1980 (J. C. Brokken-Zijp, M. J. van
275 National Cash Reg., DE-AS 1 065 115, 1956. den Brink, P. A. J. M. Hendriks, J. H. H. Meurs).
276 Sumitomo, JP 70 24 676, 1966; JP 73 29 729, 309 Hodogaya, JP 9 076/65, 1961.
1966. 310 Friedl€ander, vol. 3, p. 1011, 1016; vol. 4, p. 456.
277 Hodogaya, JP 72 04 638, 1968; JP 74 24 315, 1969. Mita 311 G. Mann, S. Hauptmann, H. Wilde, J. Lehmann, M.
Ind., JP 52 105 931, 1976. Naumann., DD 139 268, 1978; DD 139 269, 1978.
278 ICI, DE-OS 2 154 659, 1970 (N. Hughes, A. H. M. 312 R. Raue, H. Harnisch, K. H. Drexhage, Heterocycles 21
Renfrew). (1984) 167.
279 Toppan Printing, JP 57 103 895, 1980. 313 S. D€ahne, D. Leupold, Angew. Chem. 78 (1966) 1029.
280 National Cash Reg., GB 725 275, 1953. Wiggins Teape, K. Elbl, C. Krieger, H. A. Staab, Angew. Chem. 98
GB 1 429 640, 1972 (J. F. McKellar, G. G. Warburton, (1986) 1024. R. Gompper, H.-U. Wagner, Angew.
D. M. Wood); DE-OS 2 402 384, 1973 (C. Srawley). Chem. 100 (1988) 1492.
281 Aizen, JP 59 76 999, 1982. 314 Eastman Kodak, DE-OS 1 569 711, 1965 (C. E. Osborne,
282 Mita Ind., JP 79 09 062, 1971. E. R. Shelton).
Vol. 4 Azine Dyes 513

315 Eastman Kodak, DE-OS 1 619 441, 1965 (J. M. Straley, 351 Nippon Kayaku, JP 58 118 855, 1982. Sumitomo, JP 62
R. C. Harris). 192 385, 1986.
316 Eastman Kodak, DE-OS 1 619 442, 1965 (J. M. Straley, 352 Sandoz, DE-OS 3 239 321, 1981 (M. Deur).
R. C. Harris). 353 Clariant, DE-OS 19 643 344, 1996 (G. Nagl, W. Bauer,
317 Cassella, DE-AS 1 250 783, 1963 (K. Mix, M. Urban, D. Schnaitmann).
H. Vollmann). 354 Ciba-Geigy, EP 83 309, 1981 (J.-M. Adam).
318 IG Farbenind., DE 659 592, 1933 (A. Wolfram, 355 Ciba-Geigy, EP 14 678, 1979 (J.-M. Adam,
K. Bonstedt); Friedl€ander, vol. 24, p. 567. P. Galafassi).
319 Centr. Med. Res. Inst., JP 49 109 399, 1973. 356 Bayer, EP 53 743, 1980 (W. Harms, K. Wunderlich).
320 BASF, DE-OS 2 145 029, 1971 (P. Dimroth, H. Trapp). 357 Hoechst, GB 448 182, 1934. GAF, US 2 134 505, 1934
321 Hoechst, DE 517 194, 1928 (G. Kr€anzlein, H. Greune, (A. Brunner, H. Greune, M. Thiele, K. Thiess).
M. Thiele); Friedl€
ander, vol. 17, p. 942. 358 E. Schulz et al., DD 101 174, 1972.
322 Clariant, EP 1 038 923, 1999 (G. Nagl, W. Bauer, 359 ICI, DE-OS 2 122 262, 1970 (B. Parton).
P. Kempter). 360 ICI, DE-OS 2 124 080, 1970 (B. Parton).
323 Ciba-Geigy, EP 298 916, 1987 (H. Hahn, R. Blattner). 361 Clariant, WO 00/71545, 1999 (L. Hasemann).
324 Bayer, DE-OS 3 510 613, 1985 (H. D€urscheid, 362 Bayer, DE-OS 3 832 531, 1988 (H. Henk, W. Harms,
W. Harms). P. Wild).
325 Bayer, EP 296 411, 1987 (J.-W Stawitz, W. Harms). 363 Sandoz, DE-OS 3 905 673, 1989; DE-OS 4 005 551,
326 Bayer, DE-OS 3 339 923, 1983 (H. J€ager). 1989 (R. Pedrazzi). Bayer, DE-OS 3 939 700, 1989
327 BASF, EP 311 969, 1987 (U. Nahr, M. Patsch). (H. Henk, W. Harms, P. Wild). Bayer, DE-OS 4 101 067,
328 M. Xia, C. Ye, J. Chem. Res., Synop. 1999, 618. 1991 (H. J€ager).
329 BASF, EP 400 429, 1989 (M. Patsch, C. Marschner). 364 Bayer, DE-OS 4 000 481, 1990 (P. Wild, U. Claussen,
330 Nippon Kayaku, JP 61 09 84, 1984. F. W. Kr€ock).
331 E. Dietz, Proc. 11th Int. Color Symp., Montreux, 1991; 365 Clariant, WO 99/51681, 1998 (G. Schofberger).
K. Hunger, Rev. Progr. Coloration 29 (1999) 71; see 366 ICI, DE-OS 2 302 382, 1972 (B. Parton).
also: Ciba Specialty Chemicals, EP 0 874 025, 1997 367 Sumitomo, JP 57 14 654, 1980.
(F. B€abler). 368 Sumitomo, JP 2000 327936, 1999.
332 H. Nishi, Y. Hirasawa, K. Katahara, Nippon Kagaku 369 Sumitomo, EP 593 016, 1992 (K. Akahori, T. Omura,
Kaishi 1987, 911. S. Kawabata, N. Harada).
333 M. Ikeda, K. Kitahara, H. Nishi, K. Kozawa, T. Uchida, 370 ICI, DE-OS 2 503 611, 1974 (J. L. Leng, B. Parton,
J. Heterocyclic Chem. 27 (1990) 1575; M. Ikeda, D. R. A. Ridyard, J. R. Lawson); DE-OS 2 823 828, 1977
K. Kitahara, H. Nishi, J. Heterocycl. Chem. 29 (1992) (A. Greenall, J. L. Leng).
289. 371 ICI, DE-OS 2 600 490, 1975 (J. L. Leng, D. W. Shaw).
334 Nippon Kayaku, JP 62 185 088, 1986. 372 ICI, EP 84 718, 1982 (A. H. M. Renfrew).
335 Fuji Xerox, JP 05142 862, 1991. 373 ICI, DE-OS 3 018 106, 1979 (H. G. Connor).
336 Pioneer Electronic Corp., JP 07 090 254, 1993 374 Sumitomo, JP 60 181 373, 1984.
(T. Murayama, S. Yamamura, M. Ikeda). 375 Ciba-Geigy, EP 486 423, 1990 (U. Lauk).
337 Ricoh, JP 58 132 231, 1982. 376 ICI, EP 95 255, 1982 (K. Anderton, N. Hall, B. Parton,
338 Toppan Printing Co. Ltd., JP 2001 124921, 1999. A. H. M. Renfrew, M. Shaw).
339 Sumitomo, JP 58 120 673, 1982. 377 Hoechst, EP 355 735, 1988 (H. M. B€uch, H. Springer).
340 Sumitomo, JP 57 05 761, 1980. 378 Ciba-Geigy, DE-OS 2 506 098, 1974 (H. Schwander,
341 Sumitomo, DE-OS 3 211 607, 1981 (I. Sawaguchi, A. Pugin, K. Burdeska).
Y. Hayashi, T. Yoshiaki). 379 Ciba-Geigy, EP 15 232, 1979 (J.-M. Adam,
342 Pentel, JP 52 00 935, 1975. P. Galafassi).
343 Hoechst, DE-AS 2 742 575, 1977 (E. Spietschka, 380 Bayer, DE-OS 3 635 312, 1986 (W. Harms). Sumitomo,
M. Urban, E. Paulus). JA 02 238 064, 1989.
344 Hoechst, EP 504 923, 1991 (E. Dietz, M. Urban). 381 Bayer, EP 355 492, 1988 (W. Harms).
Toyo Ink, JP 04 246 469, 1991; JP 06 049 386, 382 Canon, Mitsubishi, JA 62 190 276, 1986.
1992. 383 Hoechst, DE 606 672, 1932 (G. Kr€anzlein, H. Greune,
345 Sumitomo, EP 659 842, 1993 (H. Inoue, Y. Hayashi, W. Schultheiss); Friedl€ ander, vol. 21, p. 1187.
H. Senba, K. Ito, M. Akita). 384 Hoechst, DE 637 020, 1933 (G. Kr€anzlein, H. Greune,
346 Sumitomo, JP 62 149 757, 1985. W. Schultheiss); Friedl€ ander, vol. 23, p. 710.
347 Nippon Kayaku, JP 07 331 095, 1994 (M. Ikeda, 385 BASF, DE-AS 1 034 294, 1955 (H. Fischer).
M. Oonishi). 386 Geigy, DE-AS 1 088 636, 1958 (A. Pugin, E. Stocker).
348 Bayer, DE-OS 3 444 886, 1984 (G. Franke, W. Harms). 387 Geigy, DE-AS 1 243 303, 1963 (A. Pugin, J. v. d. Crone).
349 Nippon Kayaku, JP 07 331 096, 1994 (M. Ikeda, 388 Geigy, DE-AS 1 444 772, 1963 (A. Pugin, J. v. d. Crone,
M. Oonishi). E. K. Burdeska). Ciba-Geigy, DE-OS 2 156 685, 1970
350 Sumitomo, JP 56 141 355, 1980. (K. Burdeska, A. Pugin).
514 Azine Dyes Vol. 4

389 Ciba, DE-OS 2 047 332, 1969 (S. Hari, K. Ronco). Ciba- 398 Ciba-Geigy, DE-OS 2 157 519, 1970 (A. Pugin,
Geigy, DE-OS 2 061 702, 1969 (K. Ronco, H. Tschudin). K. Burdeska, J. v. d. Crone).
390 Ciba-Geigy, DE-OS 1 644 672, 1966 (K. Ronco, I. Hari). 399 Du Pont, US 2 504 153, 1948 (G. B. Robbins).
391 Ciba, DE-OS 1 929 507, 1968 (S. Hari, K. Ronco); FR 2 400 Ricoh, JP 58 132 231, 1982.
010 714, 1968. Mitsubishi, JP 52 30 823, 1975; JP 52 401 H. Musso, D. D€opp, J. Kuhls, Chem. Ber. 98 (1965) 3937.
134 634, 1976, JP 52 140 683. 402 ICI, GB 698 200, 1951 (J. M. Fielden, D. G. Wilkinson).
392 Ciba-Geigy, DE-OS 2 322 892, 1972 (K. Burdeska,
A. Pugin).
393 Geigy, DE-AS 1 231 370, 1962 (J. v. d. Crone, A. Pugin).
PCUK, FR 2 328 710, 1975 (A. Le Pape). Further Reading
394 Bayer, WO 99/12937, 1997 (K. Kunde).
395 Bayer, WO 99/23170, 1997 (K. Kunde). H. Atacag Erkurt (ed.): Biodegradation of azo dyes, 1st ed.,
396 Ciba-Geigy, DE-OS 2 355 694, 1972 (A. Pugin, Springer, Berlin 2010.
K. Burdeska, J. v. d. Crone). S.-H. Kim (ed.): Functional dyes, 1st ed., Elsevier, Amster-
397 Mitsubishi, DE-OS 2 733 539, 1976 (S. Imahori, dam 2006.
Y. Murata, S. Suzuki, K. Yokohama); JP 53 26 826, A. R. Lang (ed.): Dyes & pigments, Nova Science Publ.,
1976; JP 53 134 971, 1977; JP 54 68 478, 1977. New York, NY 2009.