Enantioselective Annulations for Dihydroquinolones by in Situ Generation of Azolium Enolates

A convergent,
catalytic asymmetric formal [4 + 2] annulation for
the synthesis of dihydroquinolones has been developed. Carboxylic
acids can be employed as precursors to NHC enolates through an in
situ activation strategy. Simultaneous generation of a reactive aza-o-quinone methide under the basic conditions employed for
NHC generation leads to a dual activation approach.