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.