AZOMETHINE DIRECT DYES OR REDUCED PRECURSORS OF THESE
DYES OBTAINED FROM 2-AMINO-3-HYDROXYPYRIDINE, AND HAIR
DYEING PROCESS USING THESE DYES AND PRECURSORS
The invention relates to the dyeing of keratin fibres
using azomethine direct dyes or reduced precursors of
azomethine direct dyes obtained from 2-amino-
3-hydroxypyridine.
It is known practice to dye keratin fibres, and in
particular the hair, with dye compositions containing
direct dyes, according to a "direct dyeing" process.
The process conventionally used in direct dyeing
consists in applying to keratin fibres direct dyes, or
colouring molecules, which have affinity for the said
fibres, leaving them to stand on the fibres, and then
rinsing the fibres. The direct dyes used hitherto are
nitrobenzene dyes, anthraquinones, nitropyridines, dyes
of azo, xanthene, acridine or azine type or
triarylmethanebenzene-based dyes.
Other dyes are obtained from oxidation bases and
oxidation couplers, which, once condensed, are applied
onto the hair. For example, in documents FR 233 036, FR
2 262 022, FR 2 262 024, US 4 221 729 and FR 2 261 750,
diphenylamines such as leuco derivatives of
indophencls, of indoamine and of indoaniline are used
either alone or in combination with other dyes in dye
compositions. Other compounds corresponding to oxidized
derivatives of leuco derivatives such as those
described in documents FR 2 254 557 and FR 2 234 277
are also known for dyeing keratin fibres-.
The colorations that result from direct dyeing are
temporary or semi-permanent colorations, since the
nature of the interactions that bind the direct dyes to
the keratin fibre, and their desorption from the
surface and/or the core of the fibre, are responsible

for their poor dyeing power and their poor fastness
with respect to washing or to perspiration. These
direct dyes are also generally sensitive to the action
of oxidizing agents such as hydrogen peroxide, which
makes them generally unusable in lightening direct dye
compositions based on hydrogen peroxide and on a
basifying agent, which would be similar to oxidation
dyeing.
Direct dyes also have a certain lack of light
stability, associated with the poor resistance of the
chromophore to photochemical attack. In addition, their
sensitivity to light is dependent on the distribution
of their molecules, uniformly or in aggregates, in the
substrate.
Consequently, there is a real need to find direct dyes
for dyeing keratin fibres, which are light-stable, and
which are also resistant to bad weather, washing and
perspiration and sufficiently stable in the presence of
oxidizing agents such as hydrogen peroxide to be able
to obtain simultaneous lightening of the fibre with the
advantages outlined above, while at the same time
having a toxicological profile that is compatible with
cosmetic use on keratin fibres.
These aims are achieved with the present invention, one
subject of which is a process for dyeing keratin fibres
using direct dyes of formula (I):


salts thereof with an organic or mineral acid,
geometrical isomers thereof, tautomers thereof, and
solvates thereof such as the hydrates;
in which formula (I):
• R1, which may be identical or different,
represent:
- a chlorine atom;
a (C1-C3)alkyl radical optionally substituted
with one or more hydroxyl groups;
- a (C1-C3) alkoxy radical optionally substituted
with one or more hydroxyl groups;
• X, which may be identical or different, represent:
a hydroxyl radical;
a radical -NR2R3 with R2 and R3 representing,
independently of each other:
i) a hydrogen atom;
ii) a C1-C5 alkyl radical optionally
substituted with one or more groups chosen
from hydroxyl, (C1-C3) alkoxy, amino, (C1-
C3)alkylamino, di (C1-C3)alkylamino,
aminocarbonyl, carboxylic -COOH, sulfonic
-SO3H, tri (C1-C3) alkylammonium and (C1-
C3)alkylimidazolium;
a pyrrolidinyl radical optionally substituted
with a group chosen from hydroxyl, (C1-
C3)alkoxy, amino, (C1-C3)alkylamino, di(C1-
C3)alkylamino, tri(C1-C3)alkylammonium and (C1-
C3)alkylimidazolium;
• n represents an integer between 0 and 3 inclusive;
it being understood that when X and/or R2 and/or R3
comprise a cationic group, the electrical neutrality of
the compounds of formula (I) is achieved with an
anionic counterion or a mixture of anionic counterions
that are cosmetically acceptable, for instance
chlorides, bromides and sulfates.
Another subject of the invention relates to a dyeing

process using reduced precursors of colourless
azomethine dyes, which, once oxidized, generate the
compounds of formula (I) as defined above. These
precursors correspond to the compounds of formula (II):

the salts thereof with an organic or mineral acid, the
geometrical isomers thereof, the tautomers thereof, and
the solvates thereof such as the hydrates;
in which formula (II) R1, X and n are as defined
previously;
it being understood that:
when X and/or R2 and/or R3 comprise a cationic group,
the electrical neutrality of the compounds of
formula (II) is achieved with an anionic counterion
or a mixture of anionic counterions that are
cosmetically acceptable, for instance chlorides,
bromides and sulfates.
Another subject of the invention is a compound of
formula (I) or (II) as defined previously, it being
understood that the compounds of formula (I) cannot
represent compounds (1b) and (1'b):


Another subject of the invention is a dye composition
for dyeing keratin fibres, comprising, in a cosmetic
medium, at least one compound of formula (I) or (II) as
defined previously, it being understood that the
compounds of formula (I) cannot represent compounds
(lb) and (1'b) as defined previously.
The direct dyes of formula (I) make it possible to
overcome the drawbacks of the direct dyes
conventionally used previously, and lead to dyeing
results by direct dyeing that show very good resistance
to light, bad weather, perspiration and rubbing. Their
good stability with respect to oxidizing agents such as
hydrogen peroxide also allows them to be used in a
process of lightening direct dyeing.
Furthermore, it has been discovered that the reduced
form of the azomethine derivatives obtained from
2-amino-3-hydroxypyridine derivatives of formula (II) ,
used under oxidizing conditions, may also lead to
colorations that show very good resistance to light,
bad weather, washing, perspiration and rubbing.
For the purposes of the present invention, and unless
otherwise indicated:
a "salt of an organic or mineral acid" is chosen,
for example, from a solvent derived from i)
hydrochloric acid HC1, ii) hydrobromic acid HBr,
iii) sulfuric acid H2SO4, iv) alkylsulfonic acids:
Alk-S(O)2OH such as methanesulf onic acid and

ethanesulfonic acid; v) arylsulfonic acids: Ar-S(O)2OH
such as benzenesulfonic acid and toluenesulfonic
acid; vi) citric acid; vii) succinic acid; viii)
tartaric acid; ix) lactic acid; x) alkoxysulfinic
acids: Alk-O-S(O)OH such as methoxysulfinic acid
and ethoxysulfinic acid; xi) aryloxysulfinic acids
such as tolueneoxysulfinic acid and
phenoxysulfinic acid; xii) phosphoric acid H3PO4;
xiii) acetic acid CH3C(O)OH; xiv) triflic acid
CF3SO3H; and xv) tetrafluoroboric acid HBF4;
an "anionic counterion" is an anion or an anionic
group associated with the cationic charge of the
dye; more particularly, the anionic counterion is
chosen from: i) halides such as chloride or
bromide; ii) nitrates; iii) sulfonates, including
C1-C6 alkylsulfonates: Alk-S(O)2O- such as
methanesulfonate or mesylate and ethanesulfonate;
iv) arylsulfonates: Ar-S(O)2O- such as
benzenesulfonate and toluenesulfonate or tosylate;
v) citrate; vi) succinate; vii) tartrate; viii)
lactate; ix) alkyl sulfates: Alk-O-S(O)O- such as
methyl sulfate and ethyl sulfate; x) aryl
sulfates: Ar-O-S(O)O- such as benzene sulfate and
toluene sulfate; xi) alkoxy sulfates: Alk-O-S (O)2O-
such as methoxy sulfate and ethoxy sulfate; xii)
aryloxy sulfates: Ar-O-S(O)2O-; xiii) phosphate;
xiv) acetate; xv) triflate; and xvi) borates such
as a tetrafluoroborate;
an "alkyl" radical is a saturated, linear or
branched hydrocarbon-based radical, containing
from 1 to 6 carbon atoms and particularly from 1
to 3 carbon atoms, such as the methyl or ethyl
radical;
an "alkoxy" radical is an "alkyl-oxy" alkyl-O-
radical in which the alkyl part . is as defined
previously;
the alkyl, alkoxy or heterocycloalkyl radicals
followed by "optionally substituted with..." means
that the said radicals may have one or more

hydrogen atoms replaced with one or more
substituents in question, particularly one or two
substituents in question.
One subject of the invention relates to direct dyes of
formula (I) or dye precursors of formula (II).
According to a particular embodiment of the invention,
the direct dyes are of formula (II).
According to another particular embodiment of the
invention, the direct dyes are of formula (I).
One particular embodiment of the invention concerns
compounds of formula (I) or (II) for which n is zero.
According to another particular embodiment of the
invention, the compound(s) of formula (I) or (II)
contained in the composition according to the invention
is (are) such that n is 1 and R1 represents a
(C1-C3) alkyl group such as methyl.
One variant concerns compounds of formula (I) or (II)
for which X represents a hydroxyl radical.
Another variant of the invention involves compounds of
formula (I) or (II) for which X represents a radical
-NR2R3 with R2 and R3 representing, independently of
each other, i) a hydrogen atom or ii) a C1-C5 alkyl
radical optionally substituted with one or more groups
chosen from hydroxyl, (C1-C3) alkoxy, amino, (C1-
C3)alkylamino, di(C1-C3)alkylamino, aminocarbonyl,
carboxylic -COOH, sulfonic -SO3H, tri (C1-C3)alkyl-
ammonium and (C1-C3) alkylimidazolium. More particularly,
X represents a group chosen from': i) (di) (C1-
C3) (alkyl)amino; ii) (di) [hydroxy (C1-C3) alkyl]amino;
iii) (C1-C3) akylimidazolium(C1-C3) alkylamino; iv) [iV-(C1-
C3) alkyl, N- (C1-C3) akylimidazolium(C1-C3) alkyl] amino; v)
tri (C1-C3) alkylammonium(C1-C5)alkylamino and vi)

(di) [tri (C1-C3) alkylammonium (C1-C5) alkyl] amino.
According to another particular embodiment of the
invention, the compounds of formula (I) or (II) are
such that X represents a pyrrolidinyl group optionally
substituted with a tri (C1-C3) alkylammonium or (C5-
C3)alkylimidazolium group. More particularly, X
represents a pyrrolidino radical optionally substituted
with a tri (C1-C3) alkylammonium or (C1-C3) alkyl-
imidazolium group.
As examples of compounds of formula (I) or (II)
contained in the composition according to the
invention, mention may be made of the dyes (1a) to (1j)
and precursors (2a) to (2j) below, and also the salts
thereof with an organic or mineral acid, geometrical
isomers thereof, tautomers thereof and solvates thereof
such as the hydrates:

with An-, which may be identical or different,
representing an anionic counterion such as halide, An"
particularly representing a chloride.
More particularly, the dyes that are contained in the
composition are chosen from the preceding dyes (1a),
(1b), (1c), (1d), (1f), (1g) and (1i), and the dye
precursors are chosen from the preceding precursors
(2a), (2b), (2c) and (2d) and the salts thereof with an
organic or mineral acid, geometrical isomers thereof,
tautomers thereof, and solvates thereof such as
hydrates.
The compounds of formula (I) or (II) of the invention
are prepared according to the following general
synthetic routes:
1- Access to the compounds corresponding to formula
(I):
The compounds corresponding to formula (I) are
generally obtained by reacting 2-amino-
3-hydroxypyridine with a para-aminophenol derivative
(X=OH) or a para-phenylenediamine derivative (X=
NR2R3) , preferably in basic medium in the presence of an
oxidizing agent. The base used is preferentially an
aqueous solution of ammonia or of sodium hydroxide and
the oxidizing agent is preferentially chosen from
hydrogen peroxide, potassium ferricyanide, air,
ammonium persulfate and manganese oxide.

Similar synthetic approaches are described in patents
FR 2 234 277, FR 2 047 932, FR 2 106 661 and FR 2 121 101.

2- Access to the compounds corresponding to formula
(II):
The compounds corresponding to formula (II) are
generally obtained by reacting the compounds of formula
(I) with a reducing agent. This reducing agent
preferentially is sodium hydrosulfite.

Similar synthetic approaches are described in patents
FR 2 056 799, FR 2 047 932, FR 2 165 965 and FR 2 262 023.
Another subject of the invention is a dye composition
for dyeing keratin fibres, comprising, in a cosmetic
medium, at least one compound of formula (I) or (II) as
defined previously.
One subject of the invention relates to a cosmetically
acceptable composition for dyeing keratin fibres,
especially human keratin fibres such as the hair,
comprising at least one direct dye of formula (I) or a
dye precursor of formula (II).
The dye composition that is useful in the invention
generally contains an amount of dye of formula (I) or
of precursor of formula (II) of between 0.001% and 30%
relative to the total weight of the composition.
Preferably, this amount is between 0.005% and 10% by
weight and even more preferentially between 0.01% and
6% by weight relative to the total weight of the
composition.
The dye composition containing the dye of formula (I)

or the precursor of formula (II) , in particular the
precursor of formula (II), may also contain an
oxidizing agent such as hydrogen peroxide, urea
peroxide, alkali metal bromates, persalts, peracids and
oxidase enzymes.
The dye composition may also contain additional direct
dyes. These direct dyes are chosen, for example, from
neutral, acidic or cationic nitrobenzene direct dyes,
neutral, acidic or cationic azo direct dyes,
tetraazapentamethine dyes, neutral, acidic or cationic
quinone and in particular anthraquinone dyes, azine
direct dyes, triarylmethane direct dyes, indoamine
direct dyes and natural direct dyes.
Among the nitrobenzene direct dyes that may be
mentioned, in a non-limiting manner, are the following
compounds:
1,4-diamino-2-nitrobenzene, 1-amino-2-nitro-4-β-
hydroxyethylaminobenzene, 1-amino-2-nitro-4-bis (β-
hydroxyethyl)aminobenzene, 1, 4-bis(β-hydroxyethy1-
amino)-2-nitrobenzene, 1-β-hydroxyethylamino-2-nitro-4-
bis (β-hydroxyethylamino)benzene, 1-(β-hydroxyethylamino-
2-nitro-4-aminobenzene, 1-β-hydroxyethylamino-2-nitro-
4-(ethyl) (β-hydroxyethyl) aminobenzene, 1-amino-3-
methy1-4-β-hydroxyethylamino-6-nitrobenzene, 1-amino-2-
nitro-4-β-hydroxyethylamino-5-chlorobenzene, 1/2-
diamino-4-nitrobenzene, 1-amino-2-β-hydroxyethylamino-
5-nitrobenzene, 1, 2-bis (β-hydroxyethylamino) -4-nitro-
benzene, 1-amino-2-tris(hydroxymethyl)methylamino-5-
nitrobenzene, 1-hydroxy-2-amino-5-nitrobenzene, 1-
hydroxy-2-amino-4-nitrobenzene, 1-hydroxy-3-nitro-4-
aminobenzene, 1-hydroxy-2-amino-4,6-dinitrobenzene, 1-
3-hydroxyethyloxy-2-β-hydroxyethylamino-5-nitrobenzene,
1-methoxy-2-β-hydroxyethylamino-5-nitrobenzene, 1-β-
hydroxyethyloxy-3-methyl amino-4-nitrobenzene, 1-β,γ-
dihydroxypropyloxy-3-methyl amino-4-nitrobenzene, 1-β-
hydroxyethylamino-4-(3, y-dihydroxypropyloxy-2-nitro-
benzene, 1-p,Y~dihydroxypropylamino-4-trifluoromethy1-

2-nitrobenzene, 1-β-hydroxyethylamino-4-trifluoro-
methy1-2-nitrobenzene, 1-β-hydroxyethylamino-3-methy1-
2-nitrobenzene, 1 -β -aminoethylamino-5-methoxy-2 -nitro-
benzene, 1-hydroxy-2-chloro-6-ethylamino-4-nitro-
benzene, 1-hydroxy-2-chloro-6-amino-4-nitrobenzene, 1-
hydroxy-6-bis (β-hydroxyethyl) amino-3-nitrobenzene, 1-β-
hydroxyethylamino-2-nitrobenzene, 1-hydroxy-4-β-
hydroxyethylamino-3-nitrobenzene.
Among the azo direct dyes, mention may be made of the
cationic azo dyes described in patent applications
WO-95/15144, WO-95/01772 and EP-714 954 the content of
which forms an integral part of the invention.
Among these compounds, mention may be made most
particularly of the following dyes: 1,3-dimethy1-2-[[4-
(dimethylamino)phenyl]azo]-1H-imidazolium chloride,
1, 3-dimethy1-2-[(4-aminophenyl)azo]-1H-imidazolium
chloride, 1-methy1-4-[(methylphenylhydrazono)methyl]-
pyridinium methyl sulfonate.
Among the azo direct dyes, mention may also be made of
the following dyes, described in the COLOUR INDEX
INTERNATIONAL 3rd edition:
Disperse Red 17, Acid Yellow 9, Acid Black 1, Basic Red
22, Basic Red 76, Basic Yellow 57, Basic Brown 16, Acid
Yellow 36, Acid Orange 7, Acid Red 33, Acid Red 35,
Basic Brown 17, Acid Yellow 23, Acid Orange 24,
Disperse Black 9.
Mention may also be made of 1-(4'-aminodiphenylazo)-2-
methy1-4-bis (P-hydroxyethyl)aminobenzene and 4-hydroxy-
3-(2-methoxyphenylazo)-1-naphthalenesulfonic acid.
Among the quinone direct dyes, mention may be made of
the following dyes:
Disperse Red 15, Solvent Violet 13, Acid Violet 43,
Disperse Violet 1, Disperse Violet 4, Disperse Blue 1,
Disperse Violet 8, Disperse Blue 3, Disperse Red 11,

Acid Blue 62, Disperse Blue 7, Basic Blue 22, Disperse
Violet 15, Basic Blue 99, and also the following
compounds: 1-N-methylmorpholiniumpropylamino-4-hydroxy-
anthraquinone, 1-aminopropylamino-4-methylaminoanthra-
quinone, 1-aminopropylaminoanthraquinone, 5-β-hydroxy-
ethy1-1, 4-diaminoanthraquinone, 2-aminoethylamino-
anthraquinone, 1, 4-bis(β,γ-dihydroxypropylamino)-
anthraquinone.
Among the azine dyes, mention may be made of the
following compounds:
- Basic Blue 17 and Basic Red 2.
Among the triarylmethane dyes, mention may be made of
the following compounds: Basic Green 1, Acid Blue 9,
Basic Violet 3, Basic Violet 14, Basic Blue 7, Acid
Violet 49, Basic Blue 26, Acid Blue 7.
Among the indoamine dyes, mention may be made of the
following compounds:
2-p-hydroxyethlyamino-5-[bis(3-4'-hydroxyethyl)amino]-
anilino-1,4-benzoquinone;
- 2-β-hydroxyethylamino-5-(2'-methoxy-4' -amino)anilino-
1,4-benzoquinone;
3-N-(2'-chloro-4'-hydroxy)phenylacetylamino-6-methoxy-
1,4-benzoquinoneimine;
3-N- (3'-chloro-4'-methylamino)phenylureido-6-methy1-
1,4-benzoquinoneimine;
3-[4'-N-(ethyl,carbamylmethyl)amino]phenylureido-6-
methy1-1,4-benzoquinoneimine.
Among the natural direct dyes, mention may be made of
lawsone, juglone, alizarin, purpurin, carminic acid,
kermesic acid, purpurogallin, protocatechaldehyde,
indigo, isatin, curcumin, spinulosin and apigenidin.
Extracts or decoctions containing these natural dyes,
and especially henna-based poultices or extracts, may
also be used.

The dye composition may contain one or more oxidation
bases and/or one or more couplers conventionally used
for the dyeing of keratin fibres.
Among the oxidation bases, mention may be made of para-
phenylenediamines, bis(phenyl)alkylenediamines, para-
aminophenols, bis-para-aminophenols, ortho-aminophenols
and heterocyclic bases, and the addition salts thereof.
Among the couplers, mention may be made especially of
meta-phenylenediamines, meta-aminophenols, meta-
diphenols, naphthalene-based couplers and heterocyclic
couplers, and the addition salts thereof.
The coupler (s) is (are) each generally present in an
amount of between 0.001% and 10% by weight and
preferably between 0.005% and 6% by weight relative to
the total weight of the dye composition.
The oxidation base(s) present in the dye composition is
(are) each generally present in an amount of between
0.001% and 10% by weight and preferably between 0.005%
and 6% by weight relative to the total weight of the
dye composition.
In general, the addition salts of the 'oxidation bases
and couplers used in the context of the invention are
especially chosen from the salts of addition with an
acid, such as the hydrochlorides, hydrobromides,
sulfates, citrates, succinates, tartrates, lactates,
tosylates, benzenesulfonates, phosphates and acetates,
and the salts of addition with a base, such as alkali
metal hydroxides, for instance sodium hydroxide,
potassium hydroxide, ammonia, amines or alkanolamines.
The medium that is suitable for dyeing, also known as
the dye support, is a cosmetic medium generally
comprising water or a mixture of water and of at least
one organic solvent. Examples of organic solvents that

may be mentioned include lower C1-C4 alkanols, such as
ethanol and isopropanol; polyols and polyol ethers, for
instance 2-butoxyethanol, propylene glycol, propylene
glycol monomethyl ether and diethylene glycol
monomethyl ether and monomethyl ether, and also
aromatic alcohols, for instance benzyl alcohol or
phenoxyethanol, and mixtures thereof.
When they are present, the solvents are preferably
present in proportions preferably of between 1% and 40%
by weight approximately, and even more preferentially
between 5% and 30% by weight approximately, relative to
the total weight of the dye composition.'
The dye composition may also contain various adjuvants
conventionally used in hair dye compositions, such as
anionic, cationic, nonionic, amphoteric or zwitterionic
surfactants or mixtures thereof, anionic, cationic,
nonionic, amphoteric or zwitterionic polymers or
mixtures thereof, mineral or organic thickeners, and in
particular anionic, cationic, nonionic and amphoteric
polymeric associative thickeners, antioxidants,
penetrants, sequestrants, fragrances, buffers,
dispersants, conditioning agents, for instance volatile
or non-volatile, modified or unmodified silicones such
as amino silicones, film-forming agents, ceramides,
preserving agents, opacifiers and conductive polymers.
The above adjuvants are generally present in an amount
for each of them of between 0.01% and 20% by weight
relative to the weight of the composition.
Needless to say, a person skilled in the art will take
care to select this or these optional additional
compounds such that the advantageous properties
intrinsically associated with the dye composition in
accordance with the invention are not, or are not
substantially, adversely affected by the envisaged
addition (s).

The pH of the dye composition is generally between 3
and 14 approximately, and preferably between 5 and 12
approximately. It may be adjusted to the desired value
by means of acidifying or basifying agents usually used
in the dyeing of keratin fibres, or alternatively using
standard buffer systems.
According to one particular mode of the invention, when
the dye composition comprises at least one dye of
formula (I), the composition has a pH of between 6 and
11. According to another particular mode of the
invention, when the composition comprises at least one
dye precursor of formula (II), the composition has pH
of between 6 and 11.
Among the acidifying agents, examples that may be
mentioned include mineral or organic acids, for
instance hydrochloric acid, orthophosphoric acid,
sulfuric acid, carboxylic acids, for instance acetic
acid, tartaric acid, citric acid or lactic acid, and
sulfonic acids.
Among the basifying agents, examples that may be
mentioned include aqueous ammonia, alkali metal
carbonates, alkanolamines such as monoethanolamine,
diethanolamine and triethanolamine, and also
derivatives thereof, sodium hydroxide, potassium
hydroxide and the compounds of formula (γ) below:

in which Wa is a propylene residue optionally
substituted with a hydroxyl group or a C1-C4 alkyl
radical; Ra:, Ra2, Ra3 and Ra4, which may be identical or
different, represent a hydrogen atom or a C1-C4 alkyl or
C1-C4 hydroxyalkyl radical.

The dye composition may be in various forms, such as in
the form of a liquid, a cream or gel, or in any other
form that is suitable for dyeing keratin fibres, and
especially the hair.
Another subject of the invention is a process for
dyeing keratin fibres, in particular the hair, which
consists in applying to keratin materials, in the
presence or absence of an oxidizing agent, a dye
composition comprising, in a cosmetic medium, at least
one azomethine dye of formula (I) or a dye precursor of
formula (II) as defined previously.
After a leave-in time, the keratin fibres are rinsed to
reveal dyed fibres. The leave-in time is generally
between 3 and 50 minutes approximately and preferably 5
to 40 minutes approximately.
The application of the dye composition according to the
invention is generally performed at room temperature.
However, it may be performed at temperatures ranging
from 20 to 80°C.
The examples that follow serve to illustrate the
invention without, however, being limiting in nature.
The dyes of the examples below were fully characterized
via the standard spectroscopic and spectrometric
methods.
EXAMPLES
EXAMPLES OF SYNTHESIS
Example 1: synthesis of 2-amino-5-(4-hydroxypheny1-
amino) -6- (4-hydroxyphenylimino) -6-H-pyridin-
3-one (compound (1a))


5.5 g (0.05 mol) of 2-amino-3-hydroxypyridine, 5.5 g
(0.05 mol) of 4-aminophenol, 50 ml of ethanol, 25 ml of
water, 50 g of aqueous 20% NH4OH solution and 50 g of a
30% aqueous hydrogen peroxide solution (110 volumes)
are respectively added to a round-bottomed flask, with
stirring. The reaction medium is stirred for 4 hours at
room temperature and then for 25 hours at 60°C.
After cooling to room temperature, the solid formed is
filtered off, washed with petroleum ether and then
dried under vacuum over P2Ob. 4.8 g of 2-amino-5-
(4-hydroxyphenylamino)-6-(4-hydroxyphenylimino)-6H-
pyridin-3-one of formula (1a) are obtained, in the form
of a red solid.
Example 2: synthesis of 2-amino-5-(4-aminopheny1-
amino)-6-(4-aminophenylimino)-6H-pyridin-
3-one 2 (compound (1b))

5.5 g (0.05 mol) of 2-amino-3-hydroxypyridine, 10.8 g
(0.1 mol) of para-phenylenediamine, 50 ml of ethanol,
25 ml of water, 50 g of aqueous 20% NH4OH solution and
50 g of a 30% aqueous hydrogen peroxide solution
(110 volumes) are respectively added to a round-
bottomed flask, with stirring. The reaction medium is
stirred for 7 hours at room temperature and then for

15 hours at 38°C.
After cooling to room temperature, the solid formed is
filtered off, washed with petroleum ether and then
dried under vacuum over P2O5. 11 g of 2-amino-5-
(4-aminophenylamino)-6-(4-aminophenylimino)-6H-pyridin-
3-one of formula (1b) are obtained.
Example 3: synthesis of 2-amino-5-(4-aminomethy1-
phenylamino)-6-(4-aminomethylphenylimino)-
6iJ-pyridin-3-one 3 (compound (1c) )

5.5 g (0.05 mol) of 2-amino-3-hydroxypyridine and
19.5 g (0.1 mol) of para-toluenediamine are introduced
into 50 ml of ethanol and 25 ml of water. 50 g of
aqueous 20% NH4OH solution and 50 g of a 30% aqueous
hydrogen peroxide solution (110 volumes) are then
added. The reaction medium is heated at 37 °C for
6 hours 30 minutes with stirring.
After cooling to room temperature, the solid formed is
filtered off and washed with petroleum ether. The crude
product obtained is then purified by chromatography on
a column of silica (eluent: gradient ranging from CH2Cl2
to a CH2Cl2/MeOH mixture) to give 100 mg of 2-amino-5-
(4-aminomethylphenylamino)-6-(4-aminomethylphenyl-
imino) -6H-pyridin-3-one of formula (1c) .
Example 4: synthesis of 2-amino-5-(4-[bis(2-hydroxy-
ethyl)amino]phenylamino}-6-{4-[bis-
(2-hydroxyethyl)amino]phenylimino}-6H-
pyridin-3-one 4 (compound (1d))


0.55 g (0.005 mol) of 2-amino-3-hydroxypyridine and
1.96 g (0.005 mol) of 2-[(4-aminophenyl)-(2-hydroxy-
ethyl)amino]ethanol are introduced into 5 ml of ethanol
and 2.5 ml of water. 5 g of aqueous 20% NH4OH solution
and 5 g of a 30% aqueous hydrogen peroxide solution
(110 volumes) are then added. The reaction medium is
stirred at room temperature for 18 hours'.
40 ml of water are added and the solid formed is then
filtered off and washed with water.
After drying under vacuum over P2O5, 0.42 g of 2-amino-
5-{4-[bis(2-hydroxyethyl)amino]phenylamino}-6—{4-
[bis(2-hydroxyethyl)amino]phenylimino}-6H-pyridin-3-one
of formula (1d) is obtained.
Example 5: synthesis of 3-amino-5,6-bis[(4-amino-
phenyl) amino]pyridin-2-ol (compound (2b)):

10 mg (0.03 mol) of 2-amino-5-[(4-aminophenyl)amino]-6-
[(4-aminophenyl)imino]pyridin-3(6H)one are added to a
solution containing 13.5 mg of sodium hydrosulfite in
250 µl of methanol and 5 µl of an aqueous sodium

hydroxide solution. The reaction medium is stirred and
the solution is then worked up according to the usual
procedure and characterized. 3-Amino-5,6-
bis[(4-aminophenyl)amino]pyridin-2-ol (2b) is obtained.
Example 6: synthesis of 3-ammo-5, 6-bis [ (4-hydroxy-
phenyl)amino]pyridin-2-ol (compound (2a)):

10 mg (0.04 mol) of 2-amino-5-[(4-hydroxyphenyl)amino]-
6-[(4-hydroxyphenyl)imino]pyridin-3(6H)one are added to
a solution containing 13.5 mg of sodium hydrosulfite in
250 ul of methanol and 5 ul of an aqueous sodium
hydroxide solution. The reaction medium is stirred and
the solution is then worked up according to the usual
procedure and characterized. 3-Amino-5,6-bis-
[(4-hydroxyphenyl)amino]pyridin-2-ol (2a) is obtained.
Example 7 : synthesis of 3-amino-5, 6-bis ({4- [bis-
(2-hydroxyethyl)amino]phenyl}amino)pyridin-
2-ol (compound 2d)):

15 mg (0.04 mol) of (6Z)-2-amino-5-({4-[bis(2-hydroxy-
ethyl)amino]phenyl}amino)-6-({4-[bis(2-hydroxyethyl)-
amino]phenyl}imino)pyridin-3(6H)one are added to a
solution containing 13.5 mg of sodium hydrosulfite in
250 µl of methanol and 5 µl of an aqueous sodium

hydroxide solution. The reaction medium is stirred and
the solution is then worked up according to the usual
procedure and characterized. 3-Amino-5, 6-bis((4-
[bis (2-hydroxyethyl) amino] phenyl} amino) pyridin-2-ol
(2d) is obtained.
EXAMPLE OF DYEING
Dyeing in neutral medium
The dye composition (A) below is prepared using
compound (1a) synthesized previously.

(*): dye support (1) pH=7 with the dye support
constituted of:

Composition (A) is applied to locks of grey hair
containing 90% white hairs. After a leave-on time of 30
minutes, the locks are rinsed, washed with a standard
shampoo, rinsed again and then dried.

The shade obtained is given in the table below:


WE CLAIM :
1. Compound of formula (I) or (II):

salts thereof with an organic or mineral acid,
geometrical isomers thereof, tautomers thereof, and
solvates thereof such as the hydrates;
in which formulae (I) and (II):
• R1, which may be identical or different,
represent:
- a chlorine atom;
a (C1-C3) alkyl radical optionally substituted
with one or more hydroxyl groups;
- a (C1-C3)alkoxy radical optionally substituted
with one or more hydroxyl groups;
• X, which may be identical or different, represent:
a hydroxyl radical;
a radical -NR2R3 with R2 and R3 representing,
independently of each other:
i) a hydrogen atom;
ii) a C1-C5 alkyl radical optionally
substituted with one or more groups chosen
from hydroxyl, (C1-C3) alkoxy, amino, (C1-
C3)alkylamino, di (C1-C3) alkylamino,
aminocarbonyl, carboxylic -COOH, sulfonic
-SO3H, tri (C1-C3) alkylammonium and (C1-
C3) alkylimidazolium;
a pyrrolidinyl radical optionally substituted
with a group chosen from hydroxyl, (C1-
C3)alkoxy, amino, (C1-C3)alkylamino, di(C1-

C3) alkylamino, tri (C1-C3) alkylammonium and (C1-
C3)alkylimidazolium;
• n represents an integer between 0 and 3 inclusive;
it being understood that
- when X and/or R2 and/or R3 comprise a cationic group,
the electrical neutrality of the compound of formula
(I) or (II) is achieved with an anionic counterion or a
mixture of anionic counterions that are cosmetically
acceptable, and
the compounds of formula (I) cannot represent
compounds (1b) and (1'b):

2. Compound of formula (I) or (II) according to Claim
1, such that n is equal to zero.
3. Compound of formula (I) or (II) according to Claim
1, such that when n is 1, R1 represents a (C1-C3)alkyl
radical.
4. Compound of formula (I) or (II) according to any
one of the preceding claims, for which X represents a
hydroxyl radical.
5. Compound of formula (I) or (II) according to any
one of Claims 1 to 3, for which X represents a radical
-NR2R3 with R2 and R3 representing, independently of
each other, i) a hydrogen atom or ii) a C1-C5 alkyl
radical optionally substituted with one or more groups
chosen from hydroxyl, (C1-C3)alkoxy, amino, (C1-C3)alky1-

amino, di(C1-C3)alkylamino, aminocarbonyl, carboxylic
-COOH, sulfonic -SO3H, tri (C1-C3) alkylammonium and (C1-
C3)alkylimidazolium.
6. Compound of formula (I) or (II) according to any
one of Claims 1 to 3, for which X represents a
pyrrolidinyl group optionally substituted with a
tri(C1-C3) alkylammonium or (C1-C3) alkylimidazolium
group.
7. Compound of formula (I) or (II) according to any
one of the preceding claims, chosen from:

with An-, which may be identical or different,
representing an anionic counterion.
8. Dye composition for dyeing keratin fibres,
comprising, in a cosmetic medium, at least one compound
of formula (I) or (II) as defined in any one of
Claims 1 to 7.
9. Composition according to the preceding claim, in
which the compound of formula (I) or (II) is present in
an amount of between 0.001% and 30% by weight relative
to the total weight of the composition.
10. Composition according to either of Claims 8 and 9,
in which, when the composition comprises at least one
compound of formula (I) , the composition has a pH of
between 6 and 11.
11. Composition according to either of Claims 8 and 9,
in which, when the composition comprises at least one
compound of formula (II) , the composition has a pH of
between 6 and 11.

12. Composition according to any one of Claims 8 to
11, which also comprises at least one oxidizing agent.
13. Composition according to the preceding claim, in
which the oxidizing agent is chosen from hydrogen
peroxide, urea peroxide, alkali metal bromates,
persalts, peracids and oxidase enzymes.
14. Process for dyeing keratin fibres, in which a
suitable dye composition comprising at least one
compound of formula (I) or (II):

salts thereof with an organic or mineral acid,
geometrical isomers thereof, tautomers thereof, and
solvates thereof such as the hydrates;
in which formulae (I) and (II):
• R1, which may be identical or different,
represent:
- a chlorine atom;
a (C1-C3) alkyl radical optionally substituted
with one or more hydroxyl groups;
- a (C1-C3) alkoxy radical optionally substituted
with one or more hydroxyl groups;
• X, which may be identical or different, represent:
a hydroxyl radical;
a radical -NR2R3 with R2 and R3 representing,
independently of each other:

i) a hydrogen atom;
ii) a C1-C5 alkyl radical optionally
substituted with one or more groups chosen
from hydroxyl, (C1-C3) alkoxy, amino, (C1-
C3) alkylamino, di (C1-C3) alkylamino,
aminocarbonyl, carboxylic -COOH, sulfonic
-SO3H, tri (C1-C3) alkylammonium and (C1-
C3)alkylimidazolium;
a pyrrolidinyl radical optionally substituted
with a group chosen from hydroxyl, (C1-
C3)alkoxy, amino, (C1-C3)alkylamino, di(C1-
C3) alkylamino, tri (C1-C3) alkylammonium and (C1-
C3)alkylimidazolium;
• n represents an integer between 0 and 3 inclusive;
it being understood that when X and/or R2 and/or R3
comprise a cationic group, the electrical neutrality of
the compound of formula (I) or (II) is achieved with an
anionic counterion or a mixture of anionic counterions
that are cosmetically acceptable, is applied to keratin
materials.
15. Process for dyeing keratin fibres according to the
preceding claim, in which a suitable dye composition as
defined in any one of Claims 8 to 13 is applied to
keratin materials.
16. Use of a compound of formula (I) or (II) as
defined in any one of Claims 1 to 7, for dyeing keratin
fibres.

The invention relates to the dyeing of keratin fibres using azomethine direct dyes or reduced
precursors of azomethine direct dyes of formula (I) and (II) obtained from 2 -amino- 3-
hydroxypyridine. The invention relates to a dye composition comprising at least one
azomethine direct dye or a reduced precursor of an azomethine direct dye, to a process for
dyeing keratin fibres, using the said composition, and to their uses in the dyeing of keratin
fibres. This composition allows a particularly stable and fast coloration to be obtained.