Synthesis of pyrazoles from sulfonyl hydrazone and benzyl acrylate under transition-metal-free conditions.

Pyrazoles as an important class of heterocyclic compounds, are widely found in pharmaceuticals and bioactive natural products. Herein we report a [3 + 2] cycloaddition reaction for the synthesis of a series of pyrazoles, with the yield up to 77%. This approach exhibits many notable features, such as convenient operating conditions, excellent functional group compatibility and readily accessible raw materials, providing an alternative route for the construction of pyrazole derivatives.