Synthesis of tri/difluoromethyl pyrazoles by [3+2] cycloaddition of tri/difluoroacetohydrazonoyl bromides with vinyl acetates

Abstract

An efficient [3 + 2] cycloaddition reaction involving vinyl acetates with tri/difluoroacetohydrazonoyl bromides has been established. This reaction provides an efficient method for synthesis of highly valuable ring-fused fluoroalkyl pyrazoles in moderate to good yields under mild reaction conditions, exhibiting remarkable regioselectivity and broad substrate scopes. The strategy further demonstrated that tri/difluoroacetohydrazonoyl bromides are effective tri/difluoromethyl building blocks for synthesis of fluoroalkyl heterocycle compounds.