(DIS)SYMMETRIC AZOMETHINE-TYPE DIRECT DYE COMPRISING AT LEAST ONE PYRAZOLOPYRIDINE UNIT, PROCESS FOR DYEING KERATIN FIBERS USING THIS DYE

Abstract

The subject of the present invention is symmetric or dissymetric azomethine direct dyes comprising at least one pyrazolopyridine unit of formula (I), a composition comprising said dyes, a process for treating keratin fibers using said dyes, a process for preparing these compounds, synthesis intermediates and a kit. In which formula (I) X, Y.sub.1, Y.sub.2, Z.sub.1, and R.sub.1 to R.sub.5 are as defined in the description.

##STR00001##

Claims

1-19. (canceled)

20. A compound chosen from azomethine dyes comprising at least one pyrazolopyridine unit of formula (I), a leuco form, an optical isomer, a geometrical isomer, a tautomers thereof, an organic or mineral acid or base addition salt thereof, a solvate thereof, or a hydrate thereof: ##STR00037## in which formula (I): Y.sub.1 and Y.sub.2, which may be identical or different, represent a nitrogen atom or a group C(R) with R representing a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group; Z.sub.1 represents an oxygen atom or a group N(R.sub.6); when Z.sub.1 represents N(R.sub.6), then R.sub.1 and R.sub.6 optionally form, together with the nitrogen atom to which they are attached, an optionally substituted, optionally cationic, 5- to 8-membered, saturated, unsaturated or aromatic heterocycle; R.sub.1 and R.sub.6, which may be identical or different, represent: a hydrogen atom; a C.sub.1-C.sub.10 alkyl radical optionally interrupted with one or more non-adjacent heteroatoms, and/or optionally substituted; an optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cyclic radical; in particular R.sub.1 represents a (poly)hydroxy(C.sub.1-C.sub.6 alkyl) group; R.sub.2, R.sub.3, R.sub.4, and R.sub.5, which may be identical or different, each independently represent: a hydrogen atom; an optionally substituted C.sub.1-C.sub.6 alkyl radical; a group chosen from NH.sub.2, N(H)R.sub.10, N(R.sub.11)R.sub.12, OH and/or OR.sub.9, with R.sub.9 and R.sub.10 representing an optionally substituted, linear or branched C.sub.1-C.sub.6 alkyl, R.sub.11 and R.sub.12, which may be identical or different, representing an optionally substituted, linear or branched C.sub.1-C.sub.6 alkyl, it being possible for R.sub.11 and R.sub.12 to form, together with the nitrogen atom to which they are attached, a saturated, unsaturated or aromatic 5- to 8-membered heterocycle optionally containing one or more other heteroatoms or groups chosen from N, O, S, S(O).sub.2 and C(O), the heterocycle being optionally substituted; a halide and/or R.sub.2, R.sub.3, R.sub.4, and R.sub.5 form, in pairs, with adjacent radicals, an optionally substituted, saturated or unsaturated (hetero)cycle; X represents an optionally substituted aryl or optionally substituted heteroaryl radical; wherein when the compounds of formula (I) are cationic, then their electro-neutrality is provided by one or more cosmetically acceptable anions which may be identical or different; and when Y.sub.1 represents NH and Y.sub.2 represents a CH group, then X represents a group other than a pyrazolo[1,5-a]pyridin-3-yl group which is optionally substituted.

21. The compound of claim 20, wherein Y.sub.1 represents N and Y.sub.2 represents C(R)

22. The compound of claim 20, wherein Y.sub.1 and Y.sub.2 represent a group C(R).

23. The compound of claim 20, wherein X represents a group chosen from those of formula (II) or of formula (III): ##STR00038## in which formulae (II) and (III): corresponds to the point of anchorage of the group (II) or (III) to the rest of the molecule; Ar represents an aryl group optionally substituted with one or more radicals R.sub.8, which may be identical or different, R.sub.8 representing an atom or group chosen from: -halogen; OR.sub.14; NR.sub.14R.sub.15; C.sub.1-C.sub.6 alkyl optionally substituted with one or more atoms or groups, which may be identical or different, chosen from i) hydroxyls, ii) amino, iii) (C.sub.1-C.sub.6)alkylamino, iv) di(C.sub.1-C.sub.6)alkylamino, v) halogen, vi) (C.sub.1-C.sub.6)alkylimidazolyl, v) tri(C.sub.1-C.sub.6)alkylammonium An.sup., vi) (C.sub.1-C.sub.6)alkylimidazolium An.sup., vii) (C.sub.1-C.sub.6)alkylpyridinium An.sup., viii) (C.sub.1-C.sub.6)alkylpiperidinium An.sup.; carboxyl (C(O)OH); carboxamide (C(O)NR.sup.aR.sup.b) with R.sup.a and R.sup.b, which may be identical or different, representing a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group; and R.sub.9 represents: a radical OR.sub.6; or a radical NR.sub.6R.sub.7; when R.sub.9 represents NR.sub.6R.sub.7 then R.sub.6 and R.sub.7 can form, together with the nitrogen atom to which they are attached, an optionally substituted, optionally cationic, 5- to 8-membered, saturated, unsaturated or aromatic heterocycle; R.sub.6 and R.sub.7, which may be identical or different, represent: a hydrogen atom; a C.sub.1-C.sub.10 alkyl radical optionally interrupted with one or more non-adjacent heteroatoms, and/or optionally substituted with one or more groups chosen from i) hydroxyl, ii) optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cycle, iii) N(R)R, iv) N.sup.+RRR with R, R and R each independently representing a C.sub.1-C.sub.6 alkyl group; an optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cyclic radical; R.sub.10, R.sub.11, R.sub.12 and R.sub.13, which may be identical or different, represent: a hydrogen atom; an optionally substituted C.sub.1-C.sub.4 alkyl radical; a group chosen from NH.sub.2, N(H)R.sub.16, N(R.sub.17)R.sub.18, OH and OR.sub.19, with R.sub.16 and R.sub.19 independently representing an optionally substituted, linear or branched C.sub.1-C.sub.6 alkyl, R.sub.17 and R.sub.18, which may be identical or different, representing an optionally substituted, linear or branched C.sub.1-C.sub.6 alkyl, optionally R.sub.17 and R.sub.18 form, together with the nitrogen atom to which they are attached, a saturated, unsaturated or aromatic 5- to 8-membered heterocycle optionally containing one or more other heteroatoms or groups chosen from N, O, S, S(O).sub.2 and/or C(O), the heterocycle being optionally substituted; and/or R.sub.10, R.sub.11, R.sub.12, and R.sub.13 form, in pairs, with adjacent radicals, an optionally substituted, saturated or unsaturated (hetero)cycle; R.sub.14 and R.sub.15, which may be identical or different, represent an atom or group chosen from: a hydrogen atom; a linear or branched C.sub.1-C.sub.6 alkyl radical optionally substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino, (C.sub.1-C.sub.6)alkylimidazole, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup., (C.sub.1-C.sub.6)alkylimidazolium An.sup., (C.sub.1-C.sub.6)alkylpyridinium An.sup.; (C.sub.1-C.sub.6)alkylpiperidinium, An.sup.; or R.sub.14 and R.sub.15 form, together with the nitrogen to which they are attached, a cationic or non-cationic 4- to 7-membered heterocycle which may also contain one or more heteroatoms such as nitrogen, oxygen and/or sulfur, said heterocycle possibly being substituted with one or more radicals, which may be identical or different, chosen from hydroxyl, amino, (di)(C.sub.1-C.sub.6)alkylamino, C.sub.1-C.sub.6 alkoxy, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup.; (C.sub.1-C.sub.6)alkylimidazolium, An.sup.; (C.sub.1-C.sub.6)alkylpyridinium, An.sup.; or C.sub.1-C.sub.6 alkyl; R.sub.14 represents an atom or group chosen from: hydrogen; linear or branched C.sub.1-C.sub.6 alkyl which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyl, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino, (C.sub.1-C.sub.6)alkylimidazole, mono/di/tri(C.sub.1-C.sub.6)alkylammonium An.sup., (C.sub.1-C.sub.6)alkylimidazolium An.sup., (C.sub.1-C.sub.6)alkylpyridinium An.sup., (C.sub.1-C.sub.6)alkylpiperidinium An.sup.; wherein when the compounds of formula (I) are cationic, then their electro-neutrality is provided by one or more anionic counterions An.sup.; and when Y.sub.1 represents NH and Y.sub.2 represents a CH group, then X represents a radical (II).

24. The compound of claim 20, wherein X represents an aryl group of formula (II) with: Ar represents a substituted aryl group, of which at least one of the substituents R.sub.5 represents a radical OR.sub.14 and/or NR.sub.14R.sub.15, and NR.sub.14R.sub.15 are in position 4 of said aryl; R.sub.14 and R.sub.15, which may be identical or different, represent an atom or group chosen from: a hydrogen atom; a linear or branched C.sub.1-C.sub.6 alkyl radical which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino, (C.sub.1-C.sub.6)alkylimidazole, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup., (C.sub.1-C.sub.6)alkylimidazolium An.sup., (C.sub.1-C.sub.6)alkylpyridinium An.sup.; (C.sub.1-C.sub.6)alkylpiperidinium, An.sup.; or else R.sub.14 and R.sub.15 form, together with the nitrogen to which they are attached, a cationic or non-cationic 4- to 7-membered heterocycle which may also contain one or more heteroatoms such as nitrogen, oxygen and/or sulfur, said heterocycle optionally being substituted with one or more radicals, which may be identical or different, chosen from hydroxyl, amino, (di)(C.sub.1-C.sub.6)alkylamino, C.sub.1-C.sub.6 alkoxy, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup.; (C.sub.1-C.sub.6)alkylimidazolium, An.sup.; (C.sub.1-C.sub.6)alkylpyridinium, An.sup.; or C.sub.1-C.sub.6 alkyl; R.sub.14 represents an atom or group chosen from: hydrogen; linear or branched C.sub.1-C.sub.6 alkyl which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyl, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino, (C.sub.1-C.sub.6)alkylimidazole, mono/di/tri(C.sub.1-C.sub.6)alkylammonium An.sup., (C.sub.1-C.sub.6)alkylimidazolium An.sup., (C.sub.1-C.sub.6)alkylpyridinium An.sup., (C.sub.1-C.sub.6)alkylpiperidinium An.sup..

25. The compound of claim 20, wherein X represents a pyrazolopyridine group of formula (III) with R.sub.9 representing: a radical NR.sub.6R.sub.7 with R.sub.6 and R.sub.7, which form, together with the nitrogen atom to which they are attached, a saturated, optionally substituted, optionally cationic, preferably catonic, 5- to 8-membered heterocycle, or else R.sub.6 and R.sub.7, which may be identical or different, represent: a hydrogen atom; a C.sub.1-C.sub.10 alkyl radical optionally substituted with one or more groups chosen from i) hydroxyl, ii) optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cycle, iii) N(R)R, iv) N.sup.+RRR with R, R and R each independently representing a C.sub.1-C.sub.6 alkyl group; or a radical OR.sub.6 with R.sub.6 representing a C.sub.1-C.sub.10 alkyl radical optionally interrupted with one or more non-adjacent heteroatoms, and/or optionally substituted with one or more groups chosen from i) hydroxyl, ii) optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cycle, iii) N(R)R, iv) N.sup.+RRR with R, R and R each independently representing a C.sub.1-C.sub.6 alkyl group; in particular, R.sub.9 represents OR.sub.6 with R.sub.6 representing a (poly)hydroxy(C.sub.1-C.sub.6 alkyl), preferably hydroxy(C.sub.1-C.sub.6 alkyl), group; R.sub.10, R.sub.11, R.sub.12 and R.sub.13, which may be identical or different, represent an atom or group chosen from: hydrogen; halogen; linear or branched C.sub.1-C.sub.6 alkyl which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino; linear or branched C.sub.1-C.sub.6 alkoxy which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino; preferably, R.sub.10, R.sub.11, R.sub.12, and R.sub.13 represent a hydrogen atom.

26. The compound of claim 20, wherein: Z.sub.1 represents an oxygen atom or a group N(R.sub.6), preferably Z.sub.1 represents an oxygen atom; R.sub.2, R.sub.3, R.sub.4 and R.sub.5, which may be identical or different, represent an atom or group chosen from: hydrogen; halogen such as fluorine or chlorine; linear or branched C.sub.1-C.sub.6 alkyl which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, mono(C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino; or linear or branched C.sub.1-C.sub.6 alkoxy which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, mono(C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino; R.sub.1 and R.sub.6, and/or R.sub.6 and R.sub.7, which may be identical or different, represent an atom or group chosen from: a hydrogen atom; a linear or branched C.sub.1-C.sub.6 alkyl radical which may be substituted with one or more radicals, which may be identical or different, chosen from a) hydroxyls; b) amino; c) (C.sub.1-C.sub.6)alkylamino; d) di(C.sub.1-C.sub.6)alkylamino; e) (C.sub.1-C.sub.6)alkylimidazolyl; f) mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup.; g) (C.sub.1-C.sub.6)alkylimidazolium, An.sup.; (C.sub.1-C.sub.6)alkylpyridinium, An.sup.; i) (C.sub.1-C.sub.6)alkylpiperidinium, An.sup.; j) (di)(C.sub.1-C.sub.6)alkylpiperazinium, An.sup.; k) morpholino and l) (C.sub.1-C.sub.6)alkylmorpholinium; X represents a radical of formula (II) or of formula (III): ##STR00039## in which formulae (II) and (III): corresponds to the point of anchorage of the group (II) or (III) to the rest of the molecule; n represents an integer between 0 and 4; when n is greater than or equal to 2, then the radicals R.sub.8 may be identical or different; R.sub.8 represents an atom or group chosen from: 1) halogen such as fluorine or chlorine; 2) C.sub.1-C.sub.6, preferably C.sub.1-C.sub.4, alkyl, optionally substituted with one or more radicals chosen from the radicals i) hydroxyl, ii) C.sub.1-C.sub.2 alkoxy, iii) (poly)hydroxy(C.sub.2-C.sub.4)alkoxy, iv) acylamino, v) amino substituted with one or two identical or different C.sub.1-C.sub.4 alkyl radicals, optionally bearing at least one hydroxyl group, or the two radicals being able to form, with the nitrogen atom to which they are attached, a saturated or unsaturated heterocycle comprising from 5 to 7 members, preferably 5 or 6 members, optionally comprising another heteroatom identical to or different than nitrogen, vi) halogen; vii) cationic or non-cationic heterocycle, such as C.sub.1-C.sub.6 alkylimidazolium An.sup., C.sub.1-C.sub.6 alkylpyridinium An.sup., C.sub.1-C.sub.6 alkylpiperidinium An.sup.; viii) C.sub.1-C.sub.6 mono/di/trialkylammonium; 3) hydroxyl; 4) C.sub.1-C.sub.6 alkoxy optionally substituted with one or more identical or different radicals chosen from i) hydroxyl; ii) amino, iii) C.sub.1-C.sub.6 mono- or dialkylamino; iv) (C.sub.1-C.sub.6)alkylimidazole; v) mono/di/tri(C.sub.1-C.sub.6)alkylammonium; vi) (C.sub.1-C.sub.6)alkylimidazolium An.sup.; vii) (C.sub.1-C.sub.6)alkylpyridinium An.sup.; viii) (C.sub.1-C.sub.6)alkylpiperidinium An.sup.; 5) C.sub.1-C.sub.6 alkoxycarbonyl; 6) C.sub.1-C.sub.6 alkylcarbonyloxy; 7) (poly)hydroxy(C.sub.2-C.sub.4)alkoxy; 8) amino; 9) 5- or 6-membered heterocycloalkyl; 10) optionally cationic 5- or 6-membered heteroaryl, preferentially imidazolium, optionally substituted with a C.sub.1-C.sub.4 alkyl radical, preferentially methyl; 11) amino substituted with one or two identical or different C.sub.1-C.sub.6 alkyl radicals optionally bearing at least i) hydroxyl, ii) amino optionally substituted with one or two C.sub.1-C.sub.3 alkyl radicals, said alkyl radicals possibly forming, with the nitrogen atom to which they are attached, a saturated or unsaturated heterocycle comprising from 5 to 7 members, optionally comprising at least one other heteroatom different than or identical to nitrogen, iii) quaternary ammonium N.sup.+RRR, M.sup. for which R, R and R, which may be identical or different, represent a hydrogen atom or a C.sub.1-C.sub.4 alkyl group; and M.sup. represents an anionic counterion, in particular a halide, iv) optionally cationic 5- or 6-membered heteroaryl, preferentially imidazolium, optionally substituted with a C.sub.1-C.sub.4 alkyl radical, preferentially methyl; 12) quaternary ammonium N.sup.+RRR, M.sup. for which R, R, R and M.sup. are as defined previously; 13) acylamino (N(R)C(O)R) in which the radical R is a hydrogen atom or a C.sub.1-C.sub.4 alkyl radical optionally bearing at least one hydroxyl group and the radical R is a C.sub.1-C.sub.2 alkyl radical; 14) carbamoyl ((R).sub.2NC(O)) in which the radicals R, which may be identical or different, represent a hydrogen atom or a C.sub.1-C.sub.4 alkyl radical optionally bearing at least one hydroxyl group; 15) alkylsulfonylamino (RS(O).sub.2N(R)) in which the radical R represents a hydrogen atom or a C.sub.1-C.sub.4 alkyl radical optionally bearing at least one hydroxyl group and the radical R represents a C.sub.1-C.sub.4 alkyl radical or a phenyl radical; 16) aminosulfonyl ((R).sub.2NS(O).sub.2) in which the radicals R, which may be identical or different, represent a hydrogen atom or a C.sub.1-C.sub.4 alkyl radical optionally bearing at least one hydroxyl group; 17) carboxyl in acid or salified form (preferably salified with an alkali metal or a substituted or unsubstituted ammonium); 18) cyano; 19) nitro; 20) polyhaloalkyl, preferentially trifluoromethyl; 21) carboxyl; 22) phenylcarbonyloxy optionally substituted with one or more hydroxyl groups; 23) phenyloxycarbonyl optionally substituted with one or more hydroxyl groups; 24) phenyl optionally substituted with one or more hydroxyl or alkoxy groups; and 25) phenoxy; or else, when n is greater than or equal to 2, two contiguous radicals R.sub.8 form, together with the carbon atoms which bear them, an optionally substituted (hetero)cycle; R.sub.8 represents an atom or group chosen from: hydrogen; halogen; OR.sub.14; NR.sub.14R.sub.15; C.sub.1-C.sub.6 alkyl optionally substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, C.sub.1-C.sub.6 monoalkylamino or dialkylamino, halogen, C.sub.1-C.sub.6 alkylimidazole, C.sub.1-C.sub.6 trialkylammonium An.sup., C.sub.1-C.sub.6 alkylimidazolium An.sup., C.sub.1-C.sub.6 alkylpyridinium alkylpiperidinium An.sup.; carboxyl (CO.sub.2H); carboxamide (CO.sub.2NH.sub.2); R.sub.9 represents a radical OR.sub.6; or a radical NR.sub.6R.sub.7; R.sub.10, R.sub.11, R.sub.12 and R.sub.13, which may be identical or different, represent an atom or group chosen from: hydrogen; halogen; linear or branched C.sub.1-C.sub.6 alkyl which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino; or linear or branched C.sub.1-C.sub.6 alkoxy which may be substituted with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino; R.sub.14 and R.sub.15, which may be identical or different, represent an atom or group chosen from: a hydrogen atom; a linear or branched C.sub.1-C.sub.6 alkyl radical optionally substituted in particular with one or more radicals, which may be identical or different, chosen from hydroxyls, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino, (C.sub.1-C.sub.6)alkylimidazole, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup.; (C.sub.1-C.sub.6)alkylimidazolium An.sup.; (C.sub.1-C.sub.6)alkylpyridinium An.sup.; (C.sub.1-C.sub.6)alkylpiperidinium, An.sup.; or else R.sub.14 and R.sub.15 form, together with the nitrogen to which they are attached, a cationic or non-cationic 4- to 7-membered heterocycle which may also contain one or more heteroatoms such as nitrogen, oxygen and/or sulfur, said heterocycle possibly being substituted with one or more radicals, which may be identical or different, chosen from hydroxyl, amino, (di)(C.sub.1-C.sub.6)alkylamino, C.sub.1-C.sub.6 alkoxy, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup.; (C.sub.1-C.sub.6)alkylimidazolium, An.sup.; (C.sub.1-C.sub.6)alkylpyridinium, An.sup.; or C.sub.1-C.sub.6alkyl; R.sub.14 represents an atom or group chosen from: hydrogen; linear or branched C.sub.1-C.sub.6 alkyl optionally substituted in particular with one or more radicals, which may be identical or different, chosen from hydroxyl, amino, (C.sub.1-C.sub.6)alkylamino or di(C.sub.1-C.sub.6)alkylamino, (C.sub.1-C.sub.6)alkylimidazole, mono/di/tri(C.sub.1-C.sub.6)alkylammonium, An.sup., (C.sub.1-C.sub.6)alkylimidazolium An.sup., (C.sub.1-C.sub.6)alkylpyridinium An.sup., (C.sub.1-C.sub.6)alkylpiperidinium An.sup.; it being understood that: when the compounds of formula (I) are cationic, then their electro-neutrality is provided by one or more cosmetically acceptable anionic counterion anions, which may be identical or different; and when Y.sub.1 represents NH and Y.sub.2 represents a CH group, then X represents a radical (II) or (II).

27. The compound of claim 20, wherein X represents an aryl group of formula (II) or (II) with R.sub.8 representing a radical NR.sub.14R.sub.15; wherein R.sub.14 represents an atom or group chosen from i) hydrogen, and ii) (C.sub.1-C.sub.4)alkyl optionally substituted with one or more hydroxyl groups, and R.sub.15 represents an atom or group chosen from i) hydrogen, and ii) (C.sub.1-C.sub.6)alkyl optionally substituted with one or more hydroxyl groups, or a heterocycle, which is preferably cationic, such as (C.sub.1-C.sub.4)alkylimidazolium, An.sup..

28. The compound of claim 20, wherein Z.sub.1 represents a radical N(R.sub.6) and X represents a radical (III) with R.sub.9 representing a group N(R.sub.6)R.sub.7 in which R.sub.1 and R.sub.6 and/or R.sub.6 and R.sub.7 form, together with the nitrogen atom which bears them, a cationic or non-cationic heterocycle chosen from piperazinyl, piperazinium, imidazolyl, pyrrolidinyl, pyridinyl, morpholinyl, morpholinium, piperidinyl, piperidinium.

29. The compound of claim 20, wherein Z.sub.1 represents a radical N(R.sub.6) and X represents a radical (II) or (II) with R.sub.1 and R.sub.6 representing a cationic or non-cationic heterocycle.

30. The compound of claim 20, wherein the radicals R.sub.1, R.sub.6 and/or R.sub.6 is (are) chosen from a hydrogen atom, a C.sub.1-C.sub.6 alkyl radical or a C.sub.1-C.sub.6 alkyl radical substituted with one or more hydroxyl groups.

31. The compound of claim 20, wherein the azomethine dyes comprise two symmetrical pyrazolopyridine units of formulae (I) below, and also the leuco forms, optical isomers, geometrical isomers and tautomers thereof, the acid or base addition salts thereof and the solvates thereof such as hydrates: ##STR00040## in which formula (I): Z.sub.1 is chosen from an oxygen atom or a group N(R.sub.6); when Z.sub.1 represents N(R.sub.6) then R.sub.1 and R.sub.6 may form, together with the nitrogen atom to which they are attached, a cationic or non-cationic, saturated, optionally unsaturated, heterocycle comprising 5 or 6 members, optionally substituted preferably with one or more (C.sub.1-C.sub.4)alkyl groups such as piperazinium, piperidinium or morpholinium optionally substituted with a (C.sub.1-C.sub.4)alkyl group; R.sub.1 represents a C.sub.1-C.sub.6 alkyl radical, optionally interrupted with one or more non-adjacent oxygen atoms, and/or optionally substituted with: a hydroxyl radical, a di(C.sub.1-C.sub.4)alkylamino radical, a heterocycle optionally substituted with one or more C.sub.1-C.sub.4 alkyl and/or hydroxyl radicals and chosen from pyrrolidine, piperidine, morpholine, piperazine and imidazole; R.sub.6 represents: a hydrogen atom, a C.sub.1-C.sub.10 alkyl radical optionally substituted with a hydroxyl radical; R.sub.2, R.sub.3, R.sub.4 and R.sub.5 each independently represent: a hydrogen atom, a C.sub.1-C.sub.4 alkyl radical.

32. The compound of claim 20, wherein said compound is chosen from: ##STR00041## ##STR00042## ##STR00043## and also the organic or mineral acid or base addition salts thereof, the leuco forms thereof, the geometrical isomers thereof, the tautomers thereof, the solvates thereof, and the hydrates thereof, with An.sup., which may be identical or different, representing an anionic counterion.

33. A cosmetic composition comprising at least one compound of claim 20.

34. A method for dying keratin fibers, comprising applying to keratin fibers a compound chosen from azomethine dyes comprising at least one pyrazolopyridine unit of formulae (I), a leuco form, an optical isomer, a geometrical isomer, a tautomers thereof, an organic or mineral acid or base addition salt thereof, a solvate thereof, or a hydrate thereof: ##STR00044## in which formula (I): Y.sub.1 and Y.sub.2, which may be identical or different, represent a nitrogen atom or a group C(R) with R representing a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group; Z.sub.1 represents an oxygen atom or a group N(R.sub.6); when Z.sub.1 represents N(R.sub.6), then R.sub.1 and R.sub.6 optionally form, together with the nitrogen atom to which they are attached, an optionally substituted, optionally cationic, 5- to 8-membered, saturated, unsaturated or aromatic heterocycle; R.sub.1 and R.sub.6, which may be identical or different, represent: a hydrogen atom; a C.sub.1-C.sub.10 alkyl radical optionally interrupted with one or more non-adjacent heteroatoms, and/or optionally substituted; an optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cyclic radical; in particular R.sub.1 represents a (poly)hydroxy(C.sub.1-C.sub.6 alkyl) group; R.sub.2, R.sub.3, R.sub.4, and R.sub.5, which may be identical or different, each independently represent: a hydrogen atom; an optionally substituted C.sub.1-C.sub.6 alkyl radical; a group chosen from NH.sub.2, N(H)R.sub.10, N(R.sub.11)R.sub.12, OH and/or OR.sub.9, with R.sub.9 and R.sub.10 representing an optionally substituted, linear or branched C.sub.1-C.sub.6 alkyl, R.sub.11 and R.sub.12, which may be identical or different, representing an optionally substituted, linear or branched C.sub.1-C.sub.6 alkyl, it being possible for R.sub.11 and R.sub.12 to form, together with the nitrogen atom to which they are attached, a saturated, unsaturated or aromatic 5- to 8-membered heterocycle optionally containing one or more other heteroatoms or groups chosen from N, O, S, S(O).sub.2 and C(O), the heterocycle being optionally substituted; a halide and/or R.sub.2, R.sub.3, R.sub.4, and R.sub.5 form, in pairs, with adjacent radicals, an optionally substituted, saturated or unsaturated (hetero)cycle; X represents an optionally substituted aryl or optionally substituted heteroaryl radical; wherein when the compounds of formula (I) are cationic, then their electro-neutrality is provided by one or more cosmetically acceptable anions which may be identical or different; and when Y.sub.1 represents NH and Y.sub.2 represents a CH group, then X represents a group other than a pyrazolo[1,5-a]pyridin-3-yl group which is optionally substituted.

35. A process for preparing the compounds of claim 20, wherein formulae (I) is symmetrical, comprising: starting from reagent A.sub.2 of 3,4-diamino type: ##STR00045## reacting at least two molar equivalents of pyrazolo[1,5-a]pyridine compound A.sub.1 comprising an amino group in position 3 with a reagent A.sub.2 which is free in position 6 of the aromatic ring and comprising in position 2 a radical Y which is either a hydrogen atom or an electrofugal group, then maintaining the reaction medium under stirring for a time of between 5 minutes and 48 hours; and then optionally purifying reaction products (I-A); wherein in formulae A.sub.1, A.sub.2 and (I-A), the radicals R.sub.1, Z.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, Y.sub.1 and Y.sub.2 are as defined previously and that, when Y.sub.1 represents NH then Y.sub.2 cannot represent a CH group and Y represents a hydrogen atom or an electrofugal atom or group, preferably an electrofugal atom or group, such as halogen, (poly)halo(C.sub.1-C.sub.6 alkoxy), or (poly)(halo)(C.sub.1-C.sub.6 alkyl)-SO.sub.3.

36. A process for preparing the compounds of claim 20, wherein formulae (I) is symmetrical, comprising: starting from reagent A.sub.4 of 3,4-dinitro type: ##STR00046## reacting at least two molar equivalents of pyrazolo[1,5-a]pyridine compound A.sub.1 comprising an amino group in position 3 with a reagent A.sub.4 comprising in position 2 and 6 of the aromatic ring an electrofugal atom or group; then maintaining the reaction medium under stirring for a time of between 5 minutes and 48 hours; then optionally purifying the reaction product A.sub.6; reducing A.sub.5 optionally purifying compound 1; wherein R.sub.1, Z.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, X, Y, Y.sub.1 and Y.sub.2 are as defined previously, and Y and Y, which may be identical or different, represent an electrofugal atom or group, such as halogen, (poly)halo(C.sub.1-C.sub.6 alkoxy) or (poly)(halo)(C.sub.1-C.sub.6 alkyl)-SO.sub.3; and that, when Y.sub.1 represents NH then Y.sub.2 does not represent a CH group; preferably, Y.sub.1 and Y.sub.2 represent a group C(R) with R representing a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group.

37. A process for preparing compounds of claim 20, wherein formulae (I) is symmetrical or dissymmetrical, comprising: starting from reagent A.sub.2 of 3,4-diamino type: ##STR00047## reacting one molar equivalent of pyrazolo[1,5-a]pyridine compound A.sub.1 comprising an amino group in position 3 with a reagent A.sub.2 as defined previously; then maintaining the reaction medium under stirring for a time of between 5 minutes and 48 hours, and then optionally purifying the reaction product A.sub.3; reacting compound A.sub.3 with one molar equivalent of a reagent bearing a (hetero)aryl group comprising a primary amine XNH.sub.2 under the same conditions as steps 1) and 2), optionally purifying a compound of formula (I); wherein R.sub.1, Z.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, X, Y, Y.sub.1 and Y.sub.2 are as defined previously, Y and Y represent an atom or group and that, when Y.sub.1 represents NH and Y.sub.2 represents a CH group, then X represents a group other than a pyrazolo[1,5-a]pyridin-3-yl group which is optionally substituted;

38. A process for preparing compounds of claim 20, wherein formulae (I) is symmetrical or dissymmetrical, comprising: starting from reagent A.sub.4 of 3,4-dinitro type: ##STR00048## reacting one molar equivalent of pyrazolo[1,5-a]pyridine compound A.sub.1 comprising an amino group in position 3 with a reagent A.sub.4 comprising in position 2 and 6 of the aromatic ring an electrofugal atom or group; then maintaining the reaction medium under stirring for a time of between 5 minutes and 48 hours, and then optionally purifying the reaction product A.sub.5; then reacting compound A.sub.5 with one molar equivalent of a reagent bearing a (hetero)aryl group comprising a primary amine XNH.sub.2 in a polar aprotic heteroaromatic solvent such as N-methylpyrrolidine; then optionally reducing A.sub.6 to give a compound of formula (I); wherein R.sub.1, Z.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, X, Y, Y.sub.1 and Y.sub.2 are as defined previously, and Y and Y, which may be identical or different, represent an electrofugal atom or group, such as halogen, (poly)halo(C.sub.1-C.sub.6 alkoxy) or (poly)(halo)(C.sub.1-C.sub.6 alkyl)-SO.sub.3; and wherein Y.sub.1 represents NH and Y.sub.2 represents a CH group, then X represents a group other than a pyrazolo[1,5-a]pyridin-3-yl group which is optionally substituted.

39. A multi-compartment device or kit, comprising, in at least one of the compartments, the compound of claim 20.

Description

EXAMPLES

I) Examples of Synthesis

Compound (1): Synthesis of 3-[3-(4-{4-amino-3-[2-(2-hydroxyethoxy)pyrazolo[1,5-a]pyridin-3-ylimino]-6-iminocyclohexa-1,4-dienylamino}phenylamino)propyl]-1-methyl-3H-imidazol-1-ium chloride (1)

[0317] ##STR00016##

a) Synthesis of 2-[3-(5-chloro-2,4-dinitrophenylamino)pyrazolo[1,5-a]pyridin-2-yloxy]ethanol (1a)

[0318] ##STR00017##

[0319] In a 100 ml three-necked flask with magnetic stirring and equipped with a thermometer, 2--aminopyrazolo[1,5-a]pyridin-2-yloxy)ethanol (synthesis described in FR2892924) (2.13 g, 9.3 mmol, 1.1 eq) is dissolved in ethanol (20 ml). The medium is placed under argon and then N,N-diisopropylethylamine (3.1 ml, 17.7 mmol; 2.1 eq) is added, followed by 1,5-dichloro-2,4-dinitrobenzene (2 g, 8.4 mmol, 1 eq).

A precipitate forms and 40 ml of ethanol are added. After stirring for 3 h at ambient temperature, the medium is filtered on sintered glass and the precipitate is then dried in a desiccator (P.sub.2O.sub.5, vacuum, 45 C.). The compound (1a) is obtained in the form of an orange powder. The NMR and mass analyses are in accordance with the expected structure (1a).

b) Synthesis of 3-[3-(4-{5-[2-(2-hydroxyethoxy)pyrazolo[1,5-a]pyridin-3-ylamino]-2,4-dinitrophenylamino}phenylamino)propyl]-1-methyl-3H-imidazol-1-ium chloride (1b)

[0320] ##STR00018##

[0321] 170 l of N,N-diisopropylethylamine (3.2 eq) and then 500 mg (1 eq) of compound (1 a) are added, under an argon atmosphere, to a solution of 390 mg of [3-(4-aminophenylamino)propyl]-1-methyl-3H-imidazol-1-ium dihydrochloride chloride (1.2 eq) in 3 ml of N-methylpyrrolidinone. The medium is heated to 100 C. and the reaction is monitored by TLC (CH.sub.2Cl.sub.2/MeOH 98/2). After 1 h 30 at 100 C., the medium is cooled to ambient temperature and then poured onto 50 ml of isopropanol. The precipitate formed is filtered off on sintered glass so as to give, after trituration from diisopropyl ether and drying (P.sub.2O.sub.5, vacuum, 45 C.), the compound (1b) obtained in the form of a black powder. The NMR and mass analyses are in accordance with the expected structure (1b).

c) Synthesis of 3-[3-(4-{4-amino-3-[2-(2-hydroxyethoxy)pyrazolo[1,5-a]pyridin-3-ylimino]-6-iminocyclohexa-1,4-dienylamino}phenylamino)propyl]-1-methyl-3H-imidazol-1-ium chloride (1)

[0322] ##STR00019##

[0323] In a 100 ml three-necked flask equipped with a thermometer and with an argon inlet, 512 mg of nitro compound (1b) (1 eq) and 512 mg of palladium-on-carbon at 5% are added to 10 ml of methanol. The medium is heated to 60 C. and then 414 mg of ammonium formate (8 eq) are added fractionwise with a spatula.

[0324] The reaction is verified by HPLC and by TLC. When there is no more nitro compound, the reaction medium is filtered on sintered glass with a bed of celite and then the filtrate is evaporated to dryness.

[0325] The solid obtained is then purified on a neutral alumina column, eluted with a mixture of dichloromethane and methanol (100/0 to 60/40 in 45 min). The expected product (1) is obtained in the form of a black powder. The NMR and mass analyses are in accordance with the expected structure (1).

Compound (2): Synthesis of 2-{3-[2-amino-5-(4-aminophenylamino)-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (2)

[0326] ##STR00020##

a) Synthesis of 2-{3-[5-(4-aminophenylamino)-2,4-dinitrophenylamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (2b)

[0327] ##STR00021##

[0328] 2.8 ml of N,N-diisopropylethylamine (2.2 eq) and then 3 g (1 eq) of compound (1a) obtained according to the procedure described in example 1 are added, under an argon atmosphere, to a solution of 2.8 g of para-phenylenediamine dihydrochloride (1.2 eq) in 35 ml of N-methylpyrrolidinone. The medium is heated to 75 C. and the reaction is monitored by TLC (CH.sub.2Cl.sub.2/MeOH 98/2).

[0329] After 3 h at 75 C., the reaction medium is cooled to ambient temperature and then poured onto ice. The precipitate obtained is filtered off on sintered glass so as to give, after trituration from diisopropyl ether and then drying (P.sub.2O.sub.5, vacuum, 45 C.), the compound (2b) obtained in the form of a red powder. The NMR and mass analyses are in accordance with the expected structure (2b).

b) Synthesis of 2-{3-[2-amino-5-(4-aminophenylamino)-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (2)

[0330] ##STR00022##

[0331] In a 100 ml three-necked flask equipped with a thermometer and with an argon inlet, 700 mg of nitro compound (2b) (1 eq) and 700 mg of palladium-on-carbon at 5% are added to 12 ml of methanol. The medium is heated to 60 C. and then 759 mg of ammonium formate (8 eq) are added fractionwise with a spatula.

[0332] The reaction is verified by HPLC and by TLC. At the end of the reaction, the reaction medium is filtered on sintered glass with a bed of celite and then the filtrate is evaporated to dryness.

[0333] The solid obtained is then purified on a neutral alumina column, eluted with a mixture of dichloromethane and methanol (100/0 to 60/40 in 45 min).

[0334] The expected product (2) is obtained in the form of a black powder. The NMR and mass analyses are in accordance with the expected structure (2).

Compound (3): Synthesis of 2-{3-[2-amino-5-[4-(ethylisopropylamino)phenylamino]-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (3)

[0335] ##STR00023##

a) Synthesis of 2-(3-{5-[4-(isopropylmethylamino)phenylamino]-2,4-dinitrophenylamino}pyrazolo[1,5-a]pyridin-2-yloxy)ethanol (3b)

[0336] ##STR00024##

[0337] 1.8 ml of N,N-diisopropylethylamine (4.1 eq) and then 2.8 g (1 eq) of compound (1 a) as described in example 1 are added, under an argon atmosphere, to a solution of 1.83 g of N-ethyl-N-isopropyl para-phenylenediamine hydrochloride (1.2 eq) in 50 ml of N-methylpyrrolidinone. The medium is heated to 100 C. and the reaction is monitored by TLC (CH.sub.2Cl.sub.2/MeOH 98/2).

[0338] After 2 h 30 at 100 C. and cooling to ambient temperature, the reaction medium is poured onto ice. The precipitate obtained is filtered off on sintered glass so as to give, after trituration from diisopropyl ether and drying (P.sub.2O.sub.5, vacuum, 45 C.), the compound (3b) isolated in the form of a brown powder. The NMR and mass analyses are in accordance with the expected structure (3b).

b) Synthesis of 2-{3-[2-amino-5-[4-(ethylisopropylamino)phenylamino]-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (3)

[0339] ##STR00025##

[0340] In a 100 ml three-necked flask equipped with a thermometer and with an argon inlet, 1 g of nitro compound (3b) (1 eq) and 1 g of palladium-on-carbon at 5% are added to 12 ml of methanol. The medium is heated to 60 C. and then 941 mg of ammonium formate (8 eq) are added fractionwise with a spatula.

[0341] The reaction is verified by HPLC and by TLC. When there is no more nitro compound, the reaction medium is filtered on sintered glass with a bed of celite and then the filtrate is evaporated to dryness.

[0342] The solid obtained is then purified on a neutral alumina column, eluted with a mixture of dichloromethane and methanol (100/0 to 60/40 in 45 min).

[0343] The expected product (3) is thus obtained in the form of a black powder. The NMR and mass analyses are in accordance with the expected structure (3).

Compound (4): Synthesis of 2-{3-[2-amino-5-{4-[bis(2-hydroxyethyl)amino]phenylamino}-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (4)

[0344] ##STR00026##

a) Synthesis of 2-[3-(5-{4-[bis(2-hydroxyethyl)amino]phenylamino}-2,4-dinitrophenylamino)pyrazolo[1,5-a]pyridin-2-yloxy]ethanol (4b)

[0345] ##STR00027##

[0346] 4.2 ml of N,N-diisopropylethylamine (3.2 eq) are added, under an argon atmosphere, to a solution of 2.9 g of N,N-2-hydroxyethyl para-phenylenediamine sulfate (1.2 eq) in 40 ml of N-methylpyrrolidinone, and then 3 g (1 eq) of compound (1 a) previously described in example 1 are added. The medium is heated to 100 C. and the reaction is monitored by TLC (CH.sub.2Cl.sub.2/MeOH 98/2).

[0347] After 2 h at 100 C., the reaction medium is poured onto ice and the precipitate obtained is filtered off on sintered glass so as to give, after trituration from diisopropyl ether and then drying (P.sub.2O.sub.5, vacuum, 45 C.), the compound (4b) isolated in the form of an orange powder.

[0348] The NMR and mass analyses are in accordance with the expected structure (4b).

b) Synthesis of 2-{3-[2-amino-5-{4-[bis(2-hydroxyethyl)amino]phenylamino}-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (4)

[0349] ##STR00028##

[0350] In a 100 ml three-necked flask equipped with a thermometer and with an argon inlet, 1 g of nitro compound (4b) (1 eq) and 1 g of palladium-on-carbon at 5% are added to 12 ml of methanol. The medium is heated to 60 C. and then 941 mg of ammonium formate (8 eq) are added fractionwise with a spatula. The reaction is verified by HPLC and by TLC. When there is no more nitro compound, the reaction medium is filtered on sintered glass with a bed of celite and then the filtrate is evaporated to dryness. The solid obtained is then purified on a neutral alumina column, eluted with a mixture of dichloromethane and methanol (100/0 to 60/40 in 45 min).

[0351] The expected product (4) is obtained in the form of a black powder. The NMR and mass analyses are in accordance with the expected structure (4).

Compound (5): Synthesis of 2-{3-[2-amino-5-[4-(2-hydroxyethylamino)phenylamino]-4-iminocyclohexa-2,5-dien-(Z)-ylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (5)

[0352] ##STR00029##

a) Synthesis of 2-(3-{5-[4-(2-hydroxyethylamino)phenylamino]-2,4-dinitrophenylamino}pyrazolo[1,5-a]pyridin-2-yloxy)ethanol (5b)

[0353] ##STR00030##

[0354] 4.6 ml of N,N-diisopropylethylamine (3.5 eq) and then 3 g (1 eq) of compound (1 a) previously described in example 1 are added, under an argon atmosphere, to a solution of 2.28 g of N,2-hydroxyethyl para-phenylenediamine sulfate (1.2 eq) in 40 ml of N-methylpyrrolidinone. The medium is heated to 100 C. and the reaction is monitored by TLC (CH.sub.2Cl.sub.2/MeOH 98/2).

[0355] After 2 h 30 at 100 C., the reaction medium is poured onto ice. The precipitate obtained is filtered off on sintered glass so as to give, after trituration from diisopropyl ether and then drying (P.sub.2O.sub.5, vacuum, 45 C.), the compound (5b) isolated in the form of an orange powder.

[0356] The NMR and mass analyses are in accordance with the expected structure (5b).

b) Synthesis of 2-{3-[2-amino-5-[4-(2-hydroxyethylamino)phenylamino]-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (5)

[0357] ##STR00031##

[0358] In a 100 ml three-necked flask equipped with a thermometer and with an argon inlet, 1 g of nitro compound (5b) (1 eq) and 1 g of palladium-on-carbon at 5% are added to 12 ml of methanol. The medium is heated to 60 C. and then 1.24 g of ammonium formate (10 eq) are added fractionwise with a spatula.

[0359] The reaction is verified by HPLC and by TLC. When there is no more nitro compound, the reaction medium is filtered on sintered glass with a bed of celite and then the filtrate is evaporated to dryness.

[0360] The solid obtained is then purified on a neutral alumina column, eluted with a mixture of dichloromethane and methanol (100/0 to 60/40 in 45 min). The expected product (5) is thus obtained in the form of a black powder. The NMR and mass analyses are in accordance with the expected structure (5).

Compound (6): Synthesis of 2-{3-[2-amino-5-[2-(2-hydroxyethoxy)pyrazolo[1,5-a]pyridin-3-ylamino]-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (6)

[0361] ##STR00032##

a) Synthesis of 2-(3-{5-[2-(2-hydroxyethoxy)pyrazolo[1,5-a]pyridin-3-ylamino]-2,4-dinitrophenylamino}pyrazolo[1,5-a]pyridin-2-yloxy)ethanol (6b)

[0362] ##STR00033##

[0363] In a 100 ml three-necked flask equipped with a thermometer, 2--aminopyrazolo[1,5-a]pyridin-2-yloxy)ethanol (4.9 g, 21.2 mmol, 2.6 eq) is dissolved in N-methylpyrrolidinone (20 ml) with stirring. The medium is placed under argon and then N,N-diisopropylethylamine (6.7 ml, 38.9 mmol; 4.1 eq) is added, followed by 1,5-dichloro-2,4-dinitrobenzene (2 g, 8.4 mmol, 1 eq) before being brought to 50 C. After 3 h of stirring at 50 C., the reaction medium is poured onto 400 ml of ice.

[0364] The precipitate obtained is filtered off on sintered glass and then rinsed with water before being dried (P.sub.2O.sub.5, vacuum, 45 C.) so as to give the compound (6b) (orange powder).

b) Synthesis of 2-{3-[2-amino-5-[2-(2-hydroxyethoxy)pyrazolo[1,5-a]pyridin-3-ylamino]-4-iminocyclohexa-2,5-dienylideneamino]pyrazolo[1,5-a]pyridin-2-yloxy}ethanol (6)

[0365] ##STR00034##

[0366] In a 100 ml three-necked flask with magnetic stirring, equipped with a thermometer, 1 g of powdered zinc is suspended in 20 ml of butanol. The medium is heated to 100 C. and 100 l of acetic acid are added, followed by 1 g of compound (6b).

[0367] The reaction is monitored by TLC and 100 l of acetic acid are added after 1 h of reaction, followed by 300 l 2 h later.

[0368] After cooling to ambient temperature, the precipitate formed is filtered off on sintered glass, and rinsed with ethanol and then ether. The gray powder obtained is placed in a three-necked flask containing 20 ml of HCl, iPrOH 5-6 N. The new precipitate obtained is then filtered off on sintered glass, before being taken up with methanol. The solution is concentrated to dryness under vacuum, taken up in ethyl ether, and then filtered on sintered glass and dried (P.sub.2O.sub.5, vacuum, 45 C.), giving the compound (6) (black powder). The NMR and mass analyses are in accordance with the expected structure (6).

II) Examples of Dyeing Keratin Fibers

[0369] The evaluation was carried out on locks of 1 g of natural Caucasian hair comprising 90% gray hair (NG). Each dye was tested at a concentration of 0.5% by weight in a formula containing 80% of water, 15% of ethanol and 5% of benzyl alcohol. The dye composition was applied to the keratin fibers, with a leave-on time of 30 min.

[0370] Rinsing with water was carried out, followed by shampooing and again rinsing with water.

Evaluation on a Spectrocolorimeter

[0371] The values L*a*b* were measured with a Minolta CM-3610d spectrophotometer and exploited with the Spectra Magix NX software.

[0372] In this L* a* b* system, the three parameters denote, respectively, L*: the color intensity, a*: the green/red color axis, and b*: the blue/yellow color axis. For the intensity, the lower the value, the darker and more intense the color.

[0373] The variation in coloring or gain in color build-up is the difference in color between the locks of natural gray hair (NG) treated with the composition according to the invention, and the untreated locks, and is measured by (4E) according to the following equation:

E={square root over ((L*L.sub.o*).sup.2+(a*a.sub.o*).sup.2+(b*b.sub.o*).sup.2)}

[0374] In this equation, L*, a* and b* represent the values measured on NG dyed hair according to the invention, and L.sub.0*, a.sub.0* and b.sub.0* represent the values measured on the untreated locks.

[0375] The higher the value of E, the greater the gain in color build-up.

TABLE-US-00001 compound L a b E (1) 26.69 4.22 2.72 37.61 (2) 29.55 4.56 4 34.55 (4) 30.46 5.08 1.86 34.41 (5) 25.21 4.1 2.86 35.00 (6) 34.4 3.24 4.35 29.70

[0376] It appears, according to the values above, that the color build-up is very satisfactory on the keratin fibers, this being whatever the type of dye of the invention.

III) Examples of Dyeing Keratin FibersComparative Tests

[0377] 1/Preparation of the Compositions

[0378] The following dyeing compositions B, C, D, E, F (according to invention) and A (comparative) were prepared from the ingredients listed in the table below. The contents are expressed as a percentage of active material relative to the total weight of the composition.

##STR00035## ##STR00036##

TABLE-US-00002 A B C D E F Compositions (comp) (inv) (inv) (inv) (inv) (inv) Compound 1 0.5 g Compound (6) 0.5 g Compound (2) 0.5 g Compound (5) 0.5 g Compound (1) 0.5 g Compound (4) 0.5 g Pure ethyl 15 g 15 g 15 g 15 g 15 g 15 g alcohol Benzylic 5 g 5 g 5 g 5 g 5 g 5 g alcohol Water 79.5 g 79.5 g 79.5 g 79.5 g 79.5 g 79.5 g

[0379] The evaluation was carried out on locks of 1 g of natural Caucasian hair comprising 90% gray hair (NG). Each composition A to F was tested. The dye composition was applied to the keratin fibers, with a leave-on time of 30 min. Rinsing with water was carried out, followed by shampooing and again rinsing with water. The values L*a*b* were measured with a Minolta CM-3610d spectrophotometer and exploited with the Spectra Magix NX software.

[0380] Results

TABLE-US-00003 Colour of hair a* b* after treatment Composition A - Comparative 9.36 2.37 Purple Composition B - Invention 3.24 4.35 Gray Composition C - Invention 4.56 4 Brown Composition D - Invention 4.1 2.86 Brown Composition E - Invention 4.22 2.72 Brown Composition F - Invention 5.08 1.86 Brown

[0381] The results obtained show that the invention makes it possible to obtain color data a* and b* between 0 and 5.5 contrary to the comparative example composition A. Invention makes it possible to obtain gray, and brown colorations with a single direct dye, without the use of a mixture of hair dyes of different colours. Colours obtained with dyes of the invention are very esthetic and natural looking.