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

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 Bronsted 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.

Automated summary

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