Enantioselective NHC-catalyzed redox [4+2]-hetero-Diels-Alder reactions using α,β-unsaturated trichloromethyl ketones as amide equivalents

Abstract

α,β-Unsaturated trichloromethyl ketones are suitable α,β-unsaturated amide and ester equivalents in N-heterocyclic carbene (NHC)-catalyzed redox hetero-Diels-Alder reactions with azolium enolates generated from α-aroyloxyaldehydes. The initially formed syn-dihydropyranone products can be isolated, or can undergo ring-opening with benzylamine followed by aminolysis of the resulting CCl3 ketone to form a range of diamides with high diastereo- and enantioselectivity (up to >95:5 dr and >99% ee).