Enantioselective dearomative single-atom skeletal editing of benzofurans.

Abstract

One-carbon ring expansion reaction of heteroarenes involving typical dearomative cyclopropanation has gained wide attention in the past decade because this method allows the facile synthesis of various valuable ring-expanded heterocycles. However, the related catalytic asymmetric exploration remains challenging with scarce reports. Herein, we disclose an enantioselective dearomative one-carbon ring expansion of benzofurans via vinyl cations formed by copper-catalyzed cyclization of diynes, leading to practical and atom-economic assembly of an array of valuable 2H-chromenes bearing a quaternary carbon stereocenter in generally good to excellent yields with excellent enantioselectivities (up to 96% ee). Notably, this protocol not only represents an asymmetric one-carbon ring expansion reaction of heteroarenes based on alkynes, but also constitutes an enantioselective dearomative single-atom skeletal editing of benzofurans. Additionally, this reaction also features a broad substrate scope, detailed mechanism studies strongly supported by theoretical calculations, and the biological activity of the products.