N-Heterocyclic Carbene Catalyzed Cyclocondensation of α,β-Unsaturated Carboxylic Acids: Enantioselective Synthesis of Pyrrolidinone and Dihydropyridinone Derivatives

The catalytic cyclocondensation of insitu activated ,-unsaturated carboxylic acids was developed. N-heterocyclic carbenes efficiently catalyzed the generation of ,-unsaturated acyl azolium intermediates from ,-unsaturated carboxylic acids via insitu generated mixed anhydrides for the enantioselective [3+2] and [3+3] cyclocondensation with -amino ketones and alkyl(aryl)imines, respectively. The corresponding pyrrolidinones and dihydropyridinones were isolated in good yields with high to excellent enantioselectivities.