Synthesis of alkynyl cyclopropa[c]coumarins via propargyl sulfonium salts as C1 synthons†

Abstract

Herein, we present a novel approach for the preparation of alkynyl cyclopropa[c]coumarin derivatives with medium to good yields utilizing propargyl sulfonium salts as C1 synthons. Compared with Br⁻, using ClO₄⁻ as the counter anion significantly enhances the yield due to its lesser nucleophilic ability. This method features mild reaction conditions and a broad substrate scope with good diastereoselectivity when the substituted R¹ group is at the 5-position of the coumarin scaffold.