Enantioselective Crossed Photocycloadditions of Styrenic Olefins by Lewis Acid Catalyzed Triplet Sensitization

Abstract

Abstract The synthesis of unsymmetrical cyclobutanes by controlled heterodimerization of olefins remains a substantial challenge, particularly in an enantiocontrolled fashion. Shown herein is that chiral Lewis acid catalyzed triplet sensitization enables the synthesis of highly enantioenriched diarylcyclobutanes by photocycloaddition of structurally varied 2′‐hydroxychalcones with a range of styrene coupling partners. The utility of this reaction is demonstrated through the direct synthesis of a representative norlignan cyclobutane natural product.