Organocatalytic Enantioselective Synthesis of 1,3‐Oxazinanes and Hexahydropyrimidines via [4+2]‐Annulation of CyclicN‐Sulfimines

Abstract

AbstractThe first asymmetric synthetic method for enantioenriched 1,3‐oxazinane and hexahydropyrimidine derivatives via the asymmetric [4+2]‐annulation of cyclicN‐sulfimines has been established. The reaction of cyclicN‐sulfimines with δ‐hydroxy‐α,β‐unsaturated ketones afforded a wide range of enantioenriched polyheterotricyclic 1,3‐oxazinane derivatives in high yields with good to excellent enantioselectivities in the presence of a cinchonidine‐derived squaramide catalyst. This approach has been extended to the asymmetric organocatalytic [4+2]‐annulation of cyclicN‐sulfimines with δ‐NHTs‐α,β‐unsaturated ketones providing enantioenriched hexahydropyrimidines. In addition, the asymmetric [4+2]‐annulation of δ‐hydroxy‐ and δ‐NHTs‐α,β‐unsaturated ketones gave their corresponding enantioenriched 1,3‐oxazinane and hexahydropyrimidine derivatives with different absolute configurations.