The anomalous reaction of 2-phenylacrylophenone with some arylhydrazines

Abstract

The reaction of 2-phenylacrylophenone with some arylhydrazines gives a mixture of the corresponding 1-aryl-3,4-diphenyl-2-pyrazoline and 1-aryl-4,5-diphenylpyrazole. A mechanism is advanced for the formation of the latter product. The 2-pyrazoline derivatives were dehydrogenated to the parent 1-aryl-3,4-diphenylpyrazoles, the ultraviolet and proton magnetic resonance spectra of which are compared with those of the corresponding 1-aryl-4,5-diphenylpyrazoles.