Tandem Reaction of Propargyl Alcohol and N-Sulfonylhydrazone: Synthesis of Dihydropyrazole and Its Utility in the Preparation of 3,3-Diarylacrylonitrile

An efficient and straightforward strategy for the synthesis of 4-methylene-1-(phenylsulfonyl)-4,5-dihydro-1H-pyrazole from propargyl alcohol and N-sulfonylhydrazone is described. N-Sulfonyl allenamide is postulated to be the key intermediate for this tandem transformation.