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.