A ruthenium-catalyzed alkenylation-annulation approach for the synthesis of indazole derivatives via C-H bond activation.

Ruthenium catalyzed oxidative alkenylation of N-aryl pyridazinediones and N-aryl phthalazinediones with acrylates and subsequent intramolecular cyclization of the resulting product in water as a green solvent were accomplished. Diverse derivatives of pyridazino[1,2-a]indazoles and indazolo[1,2-b]phthalazines were readily prepared in moderate to high yields by this methodology from easily accessible starting materials via cascade directed C-H bond activation/annulation reactions.