CONSTRUCTION OF DIHYDROPYRIDO[2,3-D]PYRIMIDINE SCAFFOLDS VIA AZA-CLAISEN REARRANGEMENT CATALYZED BY N-HETEROCYCLIC CARBENES.

N-Heterocyclic carbenes (NHC) catalyzing aza-Claisen rearrangement of alpha,beta-unsaturated enals with cyclic vinylogous amides under oxidative condition generating potentially biologically active dihydropyridinone-fused uracils have been developed. This strategy represents an unique NHC-activation-based path with the use of 6-aminouracils as stable alpha,beta-diEWG cyclic vinylogous amides for the efficient synthesis of bicyclic N-unprotected lactams similar to many useful drugs.