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.