Thieno[2,3-c]pyrazoles and related heterocycles

Abstract

5-Chloro-3-methyl-1-phenyl-1H-pyrazole-4-carboxaldehyde (1) was converted, via the oxime 2, into the chloronitrile 3. Treatment of compound 3 with methyl thioglycolate gave the novel methyl 4-amino-3-methyl-1-phenyl-1H-thieno [2,3-c]pyrazole-5-carboxylate (4). This with 2,5-dimethoxytetrahydrofuran gave the pyrrolyl ester 5. Hydrazinolysis of the ester 5 gave the carbohydrazide derivative 6 which was used in the synthesis of substituted heterocycles.