Regiodivergent Addition of Allylic Acetals in Ruthenium-Catalyzed C–H/N–H Annulation Reaction

Distinct reaction modes of π-allylruthenium complexes,
derived
from allylic acetals, in the urazole-directed C–H/N–H
annulation are described. By controlling the reaction conditions,
electrophilic addition of π-allylruthenium complexes at the
α- and γ-positions was selectively achieved, resulting
in the formation of dihydrocinnolines and benzodiazepines, respectively.
A series of control experiments for plausible reaction mechanism were
performed.