NHC-catalyzed activation of α,β-unsaturated N-acyltriazoles: an easy access to dihydropyranones

An N-heterocyclic carbene catalyzed activation of alpha,beta-unsaturated N-acyltriazoles is described. The in situ generated alpha,beta-unsaturated acylazolium intermediates allowed an enantioselective formal [3+3] cycloaddition with 1,3-dicarbonyl compounds. The resulting dihydro-pyranones are formed in good to excellent yields and with high enantioselectivities.