Photoredox‐Catalyzed Multicomponent Cyclization of 2‐Vinyl Phenols, <i>N</i>‐Alkoxypyridinium Salts, and Sulfur Ylides for Synthesis of Dihydrobenzofurans
Fan Yuan, Dongmei Yan, Panpan Gao, De‐Qing Shi, Wen‐Jing Xiao, Jia‐Rong Chen
Abstract
Abstract The 2,3‐dihydrobenzofuran ring systems are a privileged class of oxygen heterocycles, and their synthesis continues to attract considerable effort. Herein, a visible‐light‐driven photoredox‐catalyzed radical multicomponent cyclization of 2‐vinyl phenols, N ‐alkoxypyridinium salts, and sulfur ylides is described. The key to the reaction success involves the use of both N ‐alkoxypyridinium salts and sulfur ylides as radical precursors. This redox‐neutral protocol features good functional group tolerance, easily available starting materials, simple operation, and mild reaction conditions, enabling the modular synthesis of various 2,3‐disubstituted dihydrobenzofurans. Mechanistic studies have also elucidated some of the aspects associated with the key radical intermediates.