Ruthenium(II)-Catalyzed Enantioselective γ‑Lactams Formation by Intramolecular C–H Amidation of 1,4,2-Dioxazol-5-ones

We report the Ru-catalyzed enantioselective annulation of 1,4,2-dioxazol-5-ones to furnish γ-lactams in up to 97% yield and 98% ee via intramolecular carbonylnitrene CH insertion. By employing chiral diphenylethylene diamine (dpen) as ligands bearing electron-withdrawing arylsulfonyl substituents, the reactions occur with remarkable chemo- and enantioselectivities; the competing Curtius-type rearrangement was largely suppressed. Enantioselective nitrene insertion to allylic/propargylic CH bonds was also achieved with remarkable tolerance to the CC and CC bonds.