Patent ID: 6444848
Filing Date: 2002-09-03
Classification: C07C

Abstract:
A process for the preparation of symmetrical diacylhydrazines having general formula (I):R1â€”COâ€”NHâ€”NHâ€”COâ€”R1â€ƒâ€ƒ(I) wherein:R1 represents a linear or branched C1C18 alkyl group; a linear or branched C2-C8 alkoxyalkyl group; a C2-C8 cyanoalkyl group; a C5-C8 cycloalkyl group, said cycloalkyl group optionally containing a heteroatom selected from oxygen, nitrogen and sulfur; a C6-C18 aryl group; or a C7-C20 arylalkyl or alkylaryl group, said arylalkyl or alkylaryl groups optionally substituted with one or more hydroxyl groups, or with one or more linear or branched C1-C8 alkoxyl groups; comprising the following steps: (A) reacting an ester of a carboxylic acid having general formula (II):R1â€”COâ€”OR2â€ƒâ€ƒ(II) wherein R1 has the same meanings defined above and R2 represents a linear or branched C1-C18 alkyl group, with hydrazine, in its pure or hydrated state, obtaining a monoacylhydrazine having general formula (III): R1â€”COâ€”NHâ€”NH2â€ƒâ€ƒ(III); (B) reacting the monoacylhydrazine having general formula (III) obtained in step (A), with a &bgr;-ketoester having general formula (IV):R3â€”COâ€”CH2â€”COOR4â€ƒâ€ƒ(IV) wherein R3 represents a linear or branched C1-C18 alkyl group, or a C6-C18 aryl group and R4 represents a linear or branched C1-C18 alkyl group, obtaining the desired symmetrical diacylhydrazine having general formula (I); the monoacylhydrazine having general formula (III) and the &bgr;-ketoester having general formula (IV) being used in molar ratios ranging from 1:0.5 to 1:0.8; and said step (B) being carried out in the presence of a hydrocarbon solvent at the reflux temperature of the solvent ranging from 60Â° C. to 180Â° C., for a time ranging from 20 minutes to 15 hours, obtaining the desired symmetrical diacylhydrazine having general formula (I), an alkyl-pyrazolone or an aryl-pyrazolone having general formula (V), an alcohol having general formula (VI) and water as indicated in the following reaction scheme: wherein R1, R3 and R4 have the same meanings defined above.