Phosphine‐Catalyzed [3+2] and [2+4] Annulations of γ‐Methyl Allenoates with Aryl α‐Keto Esters: Stereoselective Syntheses of Functionalized Tetrahydrofurans and 4‐Chromanols

Abstract

AbstractPhosphine‐catalyzed [3+2] and [2+4] annulation reactions of γ‐methyl allenoates with aryl α‐keto esters are described. Under the catalysis of triarylphosphine, γ‐methyl allenoates participate in both the [3+2] annulation with aroylformates and [2+4] annulation with ortho‐hydroxy aroylformates smoothly to bring about functionalized tetrahydrofurans and 4‐chromanols, respectively, in moderate to excellent yields with high stereoselectivity. The reactions herein also represent rare successful examples of phosphine‐catalyzed allene−ketone transformations, and further expand the scope of ketones in allene chemistry under phosphine catalysis.