ASYMMETRIC AZA-DIELS-ALDER REACTION - ENANTIOSELECTIVE AND DIASTEREOSELECTIVE REACTION OF IMINE MEDIATED BY CHIRAL LEWIS ACID

An efficient asymmetric aza-Diels-Alder reaction using chiral boron mediator is developed. The key to its success is the use of the chiral boron complex prepared in situ from (R)- or (S)- binaphthol and B(OPh)3. The enantiomeric reaction of prochiral imine affords products of up to 90% ee. The double asymmetric induction of chiral imine using alpha-benzylamine as a chiral auxiliary is achieved with almost complete diastereoselectivity for both aliphatic and aromatic aldimines. This method is applied to the efficient synthesis anabasine and coniine of piperidine alkaloides.