Phosphine-Mediated [2+1] Cyclization of Coumarins for the Efficient Construction of cyclopropa[c]coumarin Scaffolds

Abstract

A phosphine-mediated [2+1] annulation of coumarins with α-keto esters or isatins was reported, leveraging in situ-generated K-R adducts as key intermediates to efficiently access both cyclopropa[c]coumarin cores and spirooxindole-fused cyclopropa[c]coumarin architectures. The reaction proceeds under mild conditions, tolerates a broad substrate scope, can be scaled to gram quantity and thus exhibits pronounced practical potential.