Cascade regioselective synthesis of pyrazoles from nitroallylic acetates and N-tosyl hydrazine

A simple, practical, and regioselective synthetic protocol for the formation of pyrazoles was developed. Unlike all other previously reported reactions of nitroallylic acetates, this process was initiated by a SN2 reaction at the electrophilic γ site. A plausible mechanism for the cascade SN2-Michael synthesis is proposed.