NHC-Catalyzed Enantioselective [3 + 3] Annulation to Construct 5,6-Dihydropyrimidin-4-ones.

The unprecedented enantioselective NHC-catalyzed [3 + 3] annulation of α-bromoenals with amidines via a dual C-N bond formation is described. The protocol allows a rapid preparation of 5,6-dihydropyrimidinones in acceptable yields with good enantioselectivities.

Enantioselective NHC-Catalyzed [3+3] Annulation of α-Bromoenals with 2-Aminobenzimidazoles.

A chiral carbene-catalyzed [3+3] annulation of α-bromoenals with 2-aminobenzimidazoles providing pyrimido[1,2-a]benzimidazoles has been described. This protocol features a broad scope and good functional group tolerance. Biological studies indicated that the formed pyrimido[1,2-a]benzimidazole exhibited moderate cytotoxic activity against tumor cells.

Carbene-Catalyzed [4 + 2] Annulation of 2 H-Azirine-2-carboxaldehydes with Ketones via Azolium Aza-Dienolate Intermediate.

A new carbene-catalyzed [4 + 2] annulation of 2 H-azirine-2-carbaldehydes with ketones was developed, thus providing the 2,3-dihydro-6 H-1,3-oxazin-6-one core structures with broad scope and good to excellent yields. Notably, the azolium aza-dienolates generated from the addition of NHCs to 2 H-azirines are first uncovered.

N-Heterocyclic carbene-catalyzed annulation of ynals with amidines: access to 1,2,6-trisubstituted pyrimidin-4-ones.

An N-heterocyclic carbene-catalyzed annulation of ynals and amidines has been reported to construct pyrimidin-4-ones. The protocol features a broad substrate scope and mild conditions. Furthermore, an oxidative strategy to catalytically generate ynal-derived acyl azolium intermediates is discussed in this mechanistic study.