Cooperative N-Heterocyclic Carbene/Palladium-Catalyzed Enantioselective Umpolung Annulations.

A combination of NHC organocatalysis and transition-metal catalysis gives rise to fundamentally new cooperative reactivity and enables the regio- and enantioselective annulation reaction between enals and vinyl benzoxazinanones. The cooperative umpolung annulation eliminates mutual deactivation and leads to a diverse set of benzazepine derivatives in good yields with excellent enantioselectivities (up to 99% ee). The development of such a cooperative catalytic system dramatically expands the scope of NHC organocatalysis by opening up new metal-catalyzed reaction pathways for homoenolate intermediates.