Cooperative Photoinduced/Brønsted Acid Catalyzed Cycloaddition of Transient Thioaldehydes and <i>ortho</i>-Quinone Methides toward a Synthesis of Benzo[<i>e</i>][1,3]oxathiines

Abstract

A cooperative, one-pot approach for the in situ generation and ensuing cycloaddition of thioaldehydes and ortho-quinone methides transiently formed under irradiation with UV-A light and Brønsted acid catalysis, respectively, has been developed giving direct access to benzo[e][1,3]oxathiines in good to excellent yields and diastereoselectivity. Both electron-rich and electron-poor thioaldehydes easily react with a broad range of ortho-quinone methides at ambient temperature in a short reaction time to furnish a wide variety of S,O-heterocycles.