The chemistry of cyanoacetylenes. Part IX. Preparation of pyrazole derivatives via 1,3-dipolar cycloaddition reactions of cyanoacetylenes with diazomethane, N-phenylsydnone, and diphenylnitrilimine

Abstract

Cyanoacetylene and chlorocyanoacetylene and the corresponding propiolamides reacted with diazomethane to give exclusively 5-cyano- or-carbamoyl-pyrazoles in good yields. Although cyanoacetylenes did not react with N-phenylsydnone in refluxing benzene, in chlorobenzene at ca. 110° the expected pyrazoles were obtained. Irradiation of 2,5-diphenyltetrazole in the presence of cyanoacetylene afforded 1,3-diphenylpyrazole-5-carbonitrile. The adducts formed from cyanoacetylenes and hydrazines could not be cyclised.