Chiral Phosphoric Acid Catalyzed Addition of Dihydropyrans to <i>N</i>-Acyl Imines: Stereocontrolled Access to Enantioenriched Spirocyclic Oxazoletetrahydropyrans with Three Contiguous Stereocenters

Abstract

Dihydropyran derivatives readily undergo addition to N-acyl imines in the presence of chiral phosphoric acids. This addition process yields an attractive product that is capable of a tandem oxidative-cyclization via an epoxide intermediate.