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

The C═N double bond of 2 -imidazole has been employed as a C-electrophile for the ruthenium(II)-catalyzed [3 + 2] spiroannulation reaction of 4-phenyl-2 -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.