Ruthenium(II)/N‐Heterocyclic Carbene Catalyzed 3+2 Carbocyclization with Aromatic NH Ketimines and Internal Alkynes

Convenient and highly efficient: Indenamines were synthesized using the title reaction, which occurs at ambient temperature, in the absence of oxidants or other metal salts, and in nonpolar solvents. A proposed mechanism involves imine-directed activation of an aromatic CH bond, alkyne insertion, and carbocyclization by intramolecular imine insertion into Ru–alkenyl linkages.