Synthesis of alkynyl cyclopropa[]coumarins propargyl sulfonium salts as C1 synthons.

Herein, we present a novel approach for the preparation of alkynyl cyclopropa[]coumarin derivatives with medium to good yields utilizing propargyl sulfonium salts as C1 synthons. Compared with Br, using ClO 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 R group is at the 5-position of the coumarin scaffold.