Cyclopropanation of Propargyl Sulfonium Salts: Highly Diastereoselective Synthesis of Alkynylcyclopropanes

The first propargyl sulfur ylides involving a cyclopropanation reaction between propargyl sulfonium salts and acrylonitrile derivatives is presented. Propargyl sulfonium salts act as unusual alkyne-group-delivering reagents in this transformation. Various alkynylcyclopropanes bearing three contiguous stereocenters were constructed in moderate to high yields with excellent diastereoselectivity under mild reaction conditions.