Construction of multi-substituted pyrazoles <i>via</i> potassium carbonate-mediated [3 + 2] cycloaddition of <i>in situ</i> generated nitrile imines with cinnamic aldehydes

Abstract

A highly efficient potassium carbonate-mediated [3 + 2] cycloaddition reaction of hydrazonoyl chlorides with cinnamic aldehydes to furnish multi-substituted pyrazoles under nontoxic and mild conditions has been developed. A plausible stepwise cycloaddition reaction mechanism is proposed. This protocol featured broad substrate coverage, good functional group tolerance, wide scalability, and operational simplicity, as well as conveniently constructed pyrazole scaffolds.