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

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.