Carbene-Catalyzed [4 + 2] Annulation of 2H-Azirine-2-carboxaldehydes with Ketones via Azolium Aza-Dienolate Intermediate
摘要:
A new carbene-catalyzed [4 + 2] annulation of 2H-azirine-2-carbaldehydes with ketones was developed, thus providing the 2,3-dihydro-6H-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 2H-azirines are first uncovered.