An Unexpected N-Heterocyclic Carbene-Catalyzed Annulation of Enals and Nitroso Compounds

The N-heterocyclic carbene (NHC)-catalyzed annulation of enals with nitroso compounds in the presence of DBU in THF has been described. Unexpected seven-membered 4-azalactones were formed according to a process involving a 1,2-Bamberger-type rearrangement.