The exo-selectivity of the new non-natural chiral auxiliary (+)-(1R,endo)-2-benzonorbornenol in an asymmetric aza-Diels–Alder reaction

The recently reported compound (+)-(1R,endo)-2-benzonorbornenol (2) proved to be an efficient chiral auxiliary in the asymmetric aza-Diels–Alder reaction between cyclopentadiene and the N-benzyl imine of its glyoxylate, which afforded a virtually all-exo mixture of cycloaducts with a 1S:1R diastereomeric ratio of 63:37.