N-heterocyclic carbene catalyzed cyclocondensation of α,β-unsaturated carboxylic acids: enantioselective synthesis of pyrrolidinone and dihydropyridinone derivatives.

Abstract

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