Telescoping synthesis of 5-amino-4-nitroso-1-alkyl-1H-pyrazole salt
AssigneeThe Procter & Gamble Company
InventorsWolfram Geibel, Ingo Weber, Armin Osan, Markus Speckbacher
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Abstract
A telescoping synthesis of 5-amino-4-nitroso-1-alkyl-1H-pyrazole salt derivatives of formula (I), the compound (I) itself, and its use as an intermediate in the fabrication of 1-alkyl-4,5-diaminopyrazole salts of general formula (IX). The compounds of formula (IX) can be used as precursor dyes in oxidative hair dye compositions. R is a mono- or poly-substituted or unsubstituted, straight or branched, saturated or mono- or poly-unsaturated, alkyl group. HZ and HZ′ are organic or mineral acids.
Claims10
A telescoping process for synthesizing 5-amino-4-nitroso-1-alkyl-1H-pyrazole salt (I), the process comprising the steps of:
- a) synthesizing the intermediate 3-hydrazinylpropanenitrile (IV) via a 1,4 Michael addition using acrylonitrile (III) and hydrazine hydrate;
- b) synthesizing the intermediate 3-(2-alkylidenehydrazinyl)propanenitrile (VI) via a condensation with intermediate (IV) and aldehyde (V):
- wherein R is a mono- or poly-substituted or unsubstituted, straight or branched, saturated or mono- or poly-unsaturated alkyl group;
- c) synthesizing the intermediate 5-amino-1-alkyl-1H-pyrazole (VII) via a cyclisation with intermediate (VI) in the presence of a base;
- d) synthesizing 5-amino-4-nitroso-1-alkyl-1H-pyrazole salt (I) via a nitrosation step with intermediate (VII) in the presence of an acid HZ;
Dependencies are inferred from the claim text.