Composition for dyeing keratin fibers which contain at least one diaminopyrazole, dyeing process, novel diaminopyrazoles and process for their preparation

The process for the preparation of a 3-substituted 4,5-diaminopyrazole or an acid-addition salt thereof, having the formula:

• wherein R′1, R′2, R′3, R′4, and R′5, which may be identical or different, represent a hydrogen atom;
• a linear or branched C1-C6 alkyl radical;
• a C2-C4 hydroxyalkyl radical;
• a C2-C4 aminoalkyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, methylenedioxy or amino radical;
• or a radical
• wherein m and n are integers, which may be identical or different, from 1 to 3 inclusive, X represents an oxygen atom or an NH group, Y represents a hydrogen atom or a methyl radical and Z represents a methyl radical, a group OR or NRR′ in which R and R′, which may be identical or different, denote a hydrogen atom, a methyl radical or an ethyl radical,
• it being understood that R′1 is other than a hydrogen atom, and when R′2 represents a hydrogen atom, R′3 may then also represent an amino or C1-C4 alkylamino radical,
• R′6 represents a methyl radical,
• it being understood that in the above formula (I′):
• at least one of the radicals R′2, R′3, R′4 and R′5 represents a hydrogen atom,
• when R′2, or respectively R′4, represents a substituted or unsubstituted phenyl radical or a benzyl radical or a radical
• R′3, or respectively R′5, cannot then represent any of these three radicals,
• when R′4 and R′5 simultaneously represent a hydrogen atom, R′1 can then form, with R′2 and R′3, a hexahydropyrimidine or tetrahydroimidazole heterocycle optionally substituted with a C1-C4 alkyl or 1,2,4-tetrazole radical,
• when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C1-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen,
• when R′2, R′3, R′4 and R′5 represent a hydrogen atom or a C1-C6 alkyl radical, R′1 or R′6 may then also represent a 2-, 3-, or 4-pyridyl, 2- or 3-thienyl or 2- or 3-furyl heterocyclic residue optionally substituted with a methyl radical or alternatively a cyclohexyl radical, with the following provisos:
• (i) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a hydrogen atom, a methyl radical or an unsubstituted phenyl radical;
• (ii) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, and when R′2 represents a methyl or ethyl radical, R′3 is then other than an unsubstituted phenyl radical;
• (iii) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and R′2, R′3 and R′5 simultaneously represent a hydrogen atom, R′4 is then other than a methyl radical;
• (iv) when R′2, R′3, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′6 represents a methyl radical, R′1 is then other than a phenyl radical substituted with a chlorine atom or with a trifluoroethyl, nitro or pyridyl radical;
• (v) when R′1 represents an isopropyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a methyl radical;
• and
• (vi) when R′1 represents a methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, R′2 and R′3 are other than an ethyl radical;
• said process comprising:
• (a) reacting a 3-aminocrotononitrile with a monosubstituted hydrazine at a temperature of above 90° C. in an alcoholic solvent, to obtain a 5-aminopyrazole;
• (b) nitrosing the 5-aminopyrazole in the 4-position, by reaction with an inorganic or organic nitrite to give a 5-amino-4-nitrosopyrazole;
• and
• (c) hydrogenating, by catalytic hydrogenation, said 5-amino-4-nitrosopyrazole to obtain a 4,5-diaminopyrazole of formula (I′).

The process for the preparation of a 3-substituted 4,5-diaminopyrazole or an acid-addition salt thereof, having the formula:

• wherein R′1, R′2, R′3, R′4, and R′5, which may be identical or different, represent a hydrogen atom;
• a linear or branched C1-C6 alkyl radical;
• a C2-C4 hydroxyalkyl radical;
• a C2-C4 aminoalkyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, methylenedioxy or amino radical;
• or a radical
• wherein m and n are integers, which may be identical or different, from 1 to 3 inclusive, X represents an oxygen atom or an NH group, Y represents a hydrogen atom or a methyl radical and Z represents a methyl radical, a group OR or NRR′ in which R and R′, which may be identical or different, denote a hydrogen atom, a methyl radical or an ethyl radical,
• it being understood that R′1 is other than a hydrogen atom, and when R′2 represents a hydrogen atom, R′3 may then also represent an amino or C1-C4 alkylamino radical,
• R′6 represents a linear or branched C1-C6 alkyl radical;
• a C1-C4 hydroxyalkyl radical;
• a C1-C4 aminoalkyl radical;
• a C1-C4 dialkylamino (C1-C4) alkyl radical;
• a C1-C4 alkylamino (C1-C4) alkyl radical;
• a C1-C4 hydroxyalkylamino (C1-C4) alkyl radical;
• a C1-C4 alkoxymethyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or a C1-C4 alkylamino radical;
• a heterocycle which is thiophene, furan or pyridine, or alternatively a radical —(CH2)p—O—(CH2)q—OR″, in which p and q are integers, which may be identical or different, from 1 to 3 inclusive and R″ represents a hydrogen atom or a methyl radical,
• it being understood that R′6 is other than a methyl radical, and that in the above formula (I′):
• at least one of the radicals R′2, R′3, R′4 and R′5 represents a hydrogen atom,
• when R′2, or respectively R′4, represents a substituted or unsubstituted phenyl radical or a benzyl radical or a radical
• R′3, or respectively R′5, cannot then represent any of these three radicals,
• when R′4 and R′5 simultaneously represent a hydrogen atom, R′1 can then form, with R′2 and R′3, a hexahydropyrimidine or tetrahydroimidazole heterocycle optionally substituted with a C1-C4 alkyl or 1,2,4-tetrazole radical,
• when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C1-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen,
• when R′2, R′3, R′4 and R′5 represent a hydrogen atom or a C1-C6 alkyl radical, R′1 or R′6 may then also represent a 2-, 3-, or 4-pyridyl, 2- or 3-thienyl or 2- or 3-furyl heterocyclic residue optionally substituted with a methyl radical or alternatively a cyclohexyl radical, with the following provisos:
• (i) when R′1 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a hydrogen atom or a methyl radical, R′6 is then other than a hydroxymethyl, isobutyloxymethyl, methoxyethyloxymethyl, cyclohexyl, thiophene, pyridine or phenyl radical or phenyl radical substituted with a methyl radical or with a trifluoromethyl radical or with a chlorine atom;
• (ii) when R′1 represents an unsubstituted phenyl radical and when R′2, R′3, R′4 and R′5 simultaneously represent a hydrogen atom, R′6 is then other than an unsubstituted phenyl radical;
• (iii) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a hydrogen atom, a methyl radical or an unsubstituted phenyl radical;
• (iv) when R′4 represents a methyl radical, and when R′5 represents an unsubstituted phenyl radical, and when R′2 and R′3 simultaneously represent a hydrogen atom, and when R′1 represents a methyl radical, R′6 is then other than an unsubstituted phenyl radical or a phenyl radical substituted with a methyl, ethyl, or methoxy radical or with a chlorine atom;
• (v) when R′1 represents a pyridyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a hydrogen atom or a methyl radical, R′6 is then other than an unsubstituted phenyl radical;
• (vi) when R′1 represents an unsubstituted phenyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a benzyl radical or a phenyl radical substituted with a methyl radical or with a chlorine atom, R′6 is then other than a methyl or unsubstituted phenyl radical;
• (vii) when R′1 represents methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, R′2 and R′3 are other than an ethyl radical;
• (viii) when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C2-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen;
• (ix) when R′1 and R′2 represent a methyl radical, and when R′3, R′4, and R′5 simultaneously represent a hydrogen atom, R′6 is other then an isopropyl radical;
• said process comprising:
• (a) reacting a β-keto acetonitrile with a monosubstituted hydrazine at a temperature of from 20 to 150° C. in an alcoholic solvent, to obtain a 5-aminopyrazole;
• (b) nitrosating the 5-aminopyrazole in the 4-position to obtain a 4-nitro-5-aminopyrazole;
• and
• (c) hydrogenating, said 4-nitro-5-aminopyrazole to obtain a 4,5-diaminopyrazole of formula (I′).

The process for the preparation of a 3-substituted 4,5-diaminopyrazole or an acid-addition salt thereof, having the formula:

• wherein R′1, R′2, R′3, R′4, and R′5, which may be identical or different, represent a hydrogen atom;
• a linear or branched C1-C6 alkyl radical;
• a C2-C4 hydroxyalkyl radical;
• a C2-C4 aminoalkyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, methylenedioxy or amino radical;
• or a radical
• wherein m and n are integers, which may be identical or different, from 1 to 3 inclusive, X represents an oxygen atom or an NH group, Y represents a hydrogen atom or a methyl radical and Z represents a methyl radical, a group OR or NRR′ in which R and R′, which may be identical or different, denote a hydrogen atom, a methyl radical or an ethyl radical,
• it being understood that when R′2 represents a hydrogen atom, R′3 may then also represent an amino or C1-C4 alkylamino radical,
• R′6 represents a linear or branched C1-C6 alkyl radical;
• a C1-C4 hydroxyalkyl radical;
• a C1-C4 aminoalkyl radical;
• a C1-C4 dialkylamino (C1-C4) alkyl radical;
• a C1-C4 alkylamino (C1-C4) alkyl radical;
• a C1-C4 hydroxyalkylamino (C1-C4) alkyl radical;
• a C1-C4 alkoxymethyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or a C1-C4 alkylamino radical;
• a heterocycle which is thiophene, furan or pyridine, or alternatively a radical —(CH2)p—O—(CH2)q—OR″, in which p and q are integers, which may be identical or different, from 1 to 3 inclusive and R″ represents a hydrogen atom or a methyl radical,
• it being understood that R′6 represents a radical of high steric bulk, and that in the above formula (I′):
• at least one of the radicals R′2, R′3, R′4 and R′5 represents a hydrogen atom,
• when R′2, or respectively R′4, represents a substituted or unsubstituted phenyl radical or a benzyl radical or a radical
• R′3, or respectively R′5, cannot then represent any of these three radicals,
• when R′4 and R′5 simultaneously represent a hydrogen atom, R′1 can then form, with R′2 and R′3, a hexahydropyrimidine or tetrahydroimidazole heterocycle optionally substituted with a C1-C4 alkyl or 1,2,4-tetrazole radical,
• when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C1-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen,
• when R′2, R′3, R′4 and R′5 represent a hydrogen atom or a C1-C6 alkyl radical, R′1 or R′6 may then also represent a 2-, 3-, or 4-pyridyl, 2- or 3-thienyl or 2- or 3-furyl heterocyclic residue optionally substituted with a methyl radical or alternatively a cyclohexyl radical, with the following provisos:
• (i) when R′1 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a hydrogen atom or a methyl radical, R′6 is then other than a hydroxymethyl, isobutyloxymethyl, methoxyethyloxymethyl, cyclohexyl, thiophene, pyridine or phenyl radical or phenyl radical substituted with a methyl radical or with a trifluoromethyl radical or with a chlorine atom;
• (ii) when R′1 represents an unsubstituted phenyl radical and when R′2, R′3, R′4 and R′5 simultaneously represent a hydrogen atom, R′6 is then other than an unsubstituted phenyl radical;
• (iii) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a hydrogen atom, a methyl radical or an unsubstituted phenyl radical;
• (iv) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, and when R′2 represents a methyl or ethyl radical, R′3 is then other than an unsubstituted phenyl radical;
• (v) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and R′2, R′3 and R′5 simultaneously represent a hydrogen atom, R′4 is then other than a methyl radical;
• (vi) when R′2, R′3, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′6 represents a methyl radical, R′1 is then other than a phenyl radical substituted with a chlorine atom or with a trifluoroethyl, nitro or pyridyl radical;
• (vii) when R′1 represents a hydrogen atom, and when R′6 represents a phenyl radical or a phenyl radical substituted with a chlorine atom or with a methyl or methoxy radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a hydrogen atom or a C1-C4 alkyl or unsubstituted phenyl radical;
• (viii) when R′4 represents a methyl radical, and when R′5 represents an unsubstituted phenyl radical, and when R′2 and R′3 simultaneously represent a hydrogen atom, and when R′1 represents a hydrogen atom or a methyl radical, R′6 is then other than an unsubstituted phenyl radical or a phenyl radical substituted with a methyl, ethyl or methoxy radical or with a chlorine atom;
• (ix) when R′1 represents a pyridyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a hydrogen atom or a methyl radical, R′6 is then other than a methyl or unsubstituted phenyl radical;
• (x) when R′1 represents a methyl, ethyl or 4-aminophenyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a hydrogen atom or an unsubstituted phenyl radical, R′6 is then other than a methyl radical;
• (xi) when R′1 represents an isopropyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, at least one of the radicals R′3 and R′6 is then other than a methyl radical;
• (xii) when R′1 represents a hydrogen atom or an unsubstituted phenyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a benzyl radical or a phenyl radical substituted with a methyl radical or with a chlorine atom, R′6 is then other than a methyl or unsubstituted phenyl radical;
• (xiii) when R′1 represents a methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, R′2 and R′3 are other than an ethyl radical;
• (xiv) when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C1-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen;
• (xv) when R′1 and R′2 represent a methyl radical, and when R′3, R′4, and R′5 simultaneously represent a hydrogen atom, R′6 is other then an isopropyl radical;
• and
• (xvi) when R′1, R′2, R′4 and R′5 silmultaneously represent a hydrogen atom and when R′3 represents a hydrogen atom, a hydroxybutyl radical, or a methyl radical, R′6 is then other than a cyclohexylisopropyl radical,
• said process comprising:
• (a) reacting a β-keto acetonitrile with a monosubstituted hydrazine to obtain a 5-aminopyrazole;
• (b) acetylating said 5-aminopyrazole in the 5-position to obtain a 5-acetylaminopyrazole;
• (c) nitrating said 5-acetylaminopyrazole in the 4-position and deacetylating said 5-acetylaminopyrazole in the 5-position to obtain a 5-amino-4-nitropyrazole;
• and
• (d) hydrogenating, said 5-amino-4-nitropyrazole to obtain a 4,5-diaminopyrazole of formula (I′).

The process for the preparation of a 3-substituted 4,5-diaminopyrazole or an acid-addition salt thereof, having the formula:

• wherein R′1, R′2, R′3, R′4, and R′5, which may be identical or different, represent a hydrogen atom;
• a linear or branched C1-C6 alkyl radical;
• a C2-C4 hydroxyalkyl radical;
• a C2-C4 aminoalkyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, methylenedioxy or amino radical;
• or a radical
• wherein m and n are integers, which may be identical or different, from 1 to 3 inclusive, X represents an oxygen atom or an NH group, Y represents a hydrogen atom or a methyl radical and Z represents a methyl radical, a group OR or NRR′ in which R and R′, which may be identical or different, denote a hydrogen atom, a methyl radical or an ethyl radical,
• it being understood that one of the radicals R′2 or R′3 is other than a hydrogen atom, and when R′2 represents a hydrogen atom, R′3 may then also represent an amino or C1-C4 alkylamino radical,
• R′6 represents a linear or branched C1-C6 alkyl radical;
• a C1-C4 hydroxyalkyl radical;
• a C1-C4 aminoalkyl radical;
• a C1-C4 dialkylamino (C1-C4) alkyl radical;
• a C1-C4 alkylamino (C1-C4) alkyl radical;
• a C1-C4 hydroxyalkylamino (C1-C4) alkyl radical;
• a C1-C4 alkoxymethyl radical;
• a phenyl radical;
• a phenyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or C1-C4 alkylamino radical;
• a benzyl radical;
• a benzyl radical substituted with a halogen atom or with a C1-C4 alkyl, C1-C4 alkoxy, nitro, trifluoromethyl, amino or a C1-C4 alkylamino radical;
• a heterocycle which is thiophene, furan or pyridine, or alternatively a radical —(CH2)p—O—(CH2)q—OR″, in which p and q are integers, which may be identical or different, from 1 to 3 inclusive and R″ represents a hydrogen atom or a methyl radical, wherein said at least one oxidation base is present in an amount effective to dye said keratin fibers,
• it being understood that in the above formula (I′):
• at least one of the radicals R′2, R′3, R′4 and R′5 represents a hydrogen atom,
• when R′2, or respectively R′4, represents a substituted or unsubstituted phenyl radical or a benzyl radical or a radical
• R′3, or respectively R′5, cannot then represent any of these three radicals,
• when R′4 and R′5 simultaneously represent a hydrogen atom, R′1 can then form, with R′2 and R′3, a hexahydropyrimidine or tetrahydroimidazole heterocycle optionally substituted with a C1-C4 alkyl or 1,2,4-tetrazole radical,
• when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C1-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen,
• when R′2, R′3, R′4 and R′5 represent a hydrogen atom or a C1-C6 alkyl radical, R′1 or R′6 may then also represent a 2-, 3-, or 4-pyridyl, 2- or 3-thienyl or 2- or 3-furyl heterocyclic residue optionally substituted with a methyl radical or alternatively a cyclohexyl radical, with the following provisos:
• (i) when R′1 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a hydrogen atom or a methyl radical, R′6 is then other than a hydroxymethyl, isobutyloxymethyl, methoxyethyloxymethyl, cyclohexyl, thiophene, pyridine or phenyl radical or phenyl radical substituted with a methyl radical or with a trifluoromethyl radical or with a chlorine atom;
• (ii) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a hydrogen atom, a methyl radical or an unsubstituted phenyl radical;
• (iii) when R′1 represents an unsubstituted phenyl radical, and when R′6 represents a methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, and when R′2 represents a methyl or ethyl radical, R′3 is then other than an unsubstituted phenyl radical;
• (iv) when R′1 represents a hydrogen atom, and when R′6 represents a phenyl radical or a phenyl radical substituted with a chlorine atom or with a methyl or methoxy radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, R′3 is then other than a hydrogen atom or a C1-C4 alkyl or unsubstituted phenyl radical;
• (v) when R′1 represents a pyridyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a methyl radical, R′6 is then other than a methyl or unsubstituted phenyl radical;
• (vi) when R′1 represents a methyl, ethyl or 4-aminophenyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents an unsubstituted phenyl radical, R′6 is then other than a methyl radical;
• (vii) when R′1 represents an isopropyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, at least one of the radicals R′3 and R′6 is then other than a methyl radical;
• (viii) when R′1 represents a hydrogen atom or an unsubstituted phenyl radical, and when R′2, R′4 and R′5 simultaneously represent a hydrogen atom, and when R′3 represents a benzyl radical or a phenyl radical substituted with a methyl radical or with a chlorine atom, R′6 is then other than a methyl or unsubstituted phenyl radical;
• (ix) when R′1 represents a methyl radical, and when R′4 and R′5 simultaneously represent a hydrogen atom, R′2 and R′3 are other than an ethyl radical;
• (x) when R′1 is hydrogen, a C1-C6 alkyl radical, or a C2-C4 hydroxyalkyl radical and when R′6 is a C1-C6 alkyl radical, a C1-C4 hydroxyalkyl radical, a phenyl radical, a substituted phenyl radical, a benzyl radical, or a substituted benzyl radical, then at least one of R′2, R′3, R′4 or R′5 is not hydrogen;
• (xi) when R′1 and R′2 represent a methyl radical, and when R′3, R′4, and R′5 simultaneously represent a hydrogen atom, R′6 is other then an isopropyl radical;
• and
• (xii) when R′1, R′2, R′4 and R′5 simultaneously represent a hydrogen atom and when R′3 represents a hydroxybutyl radical, or a methyl radical, R′6 is then other than a cyclohexylisopropyl radical,
• said process comprising:
• (a) reacting a β-keto ester with a hydrazine to obtain a 5-hydroxypyrazole in equilibrium with its 5-pyrazolone tautomeric form;
• (b) nitrating said 5-hydroxypyrazole in the 4-position;
• (c) chlorinating said 5-hydroxypyrazole in the 5-position to obtain a 5-chloro-4-nitropyrazole;
• (d) converting said 5-chloro-4-nitropyrazole, in the presence of a primary amine H2N—R′3, to a 5-amino-4-nitropyrazole;
• and
• (e) hydrogenating, by catalytic hydrogenation, said 5-amino-4-nitropyrazole to obtain a 4,5-diaminopyrazole of formula (I′).