Regioselective Synthesis of Sulfonylpyrazoles via Base Mediated Reaction of Diazosulfones with Nitroalkenes and a Facile Entry into Withasomnine

A base mediated reaction of alpha-diazo-beta-ketosulfone with nitroalkenes affords sulfonylpyrazoles as single regioisomers in excellent yield in a one-pot room temperature reaction. Aryl, heteroaryl, styrenyl, alkyl, hydroxymethyl, and hydrazinyl groups could be introduced on the pyrazole ring by the appropriate choice of nitroalkenes. Synthesis of sulfonylpyrazole fused to other heterocycles and application of the methodology to an expedient synthesis of a pyrazole alkaloid, Withasomnine, are also reported.