Ruthenium(II)-Catalyzed Regioselective [3 + 2] Spiroannulation of 2H‑Imidazoles with 2‑Alkynoates

The CN double bond of 2H-imidazole has been employed as a C-electrophile for the ruthenium­(II)-catalyzed [3 + 2] spiroannulation reaction of 4-phenyl-2H-imidazoles and 2-alkynoates to synthesize spiroimidazole-4,1′-indenes. This strategy features high regioselectivity, broad functional group tolerance, and use of ruthenium as a catalyst, providing a new method to synthesize spirocycles with potential applications in pharmaceuticals.