Copper-Catalysed Decarboxylative Alkynylation-Cyclization Reaction of Propargylic Cyclic Carbonates with Nitrile Imines to Access Tetrasubstituted Pyrazoles

Abstract

Tetrasubstituted pyrazoles are valuable scaffolds in pharmaceuticals and agrochemicals, yet their regioselective synthesis remains challenging. Herein, we report a copper-catalyzed decarboxylative alkynylation-cyclization reaction of propargylic cyclic carbonates with nitrile imines, enabling efficient access to diverse tetrasubstituted pyrazoles under mild conditions. This three-molecular protocol exhibits broad substrate scope, excellent functional group tolerance, and high efficiency. Mechanistic studies support a sequential process in which a copper-allenylidene intermediate mediates migratory insertion of propargylic cyclic carbonate, followed by [3+2] cycloaddition with nitrile imine, copper migration, and β-OH elimination. This strategy provides a versatile platform for synthesizing complex pyrazole architectures, promising applications in drug discovery and materials science.