Ruthenium(II)-Catalyzed CH Bond Activation: An Efficient Route toward Indenamines

An efficient and atom-economical method for the synthesis of substituted indenamines from N-tosylarylimines and alkynes via ruthenium(II)-catalyzed CH bond activation and annulation is described. The catalytic reaction proceeds well with a broad substrate scope and in good yields. A possible mechanism is proposed that involves imine nitrogen chelation-assisted ortho-CH bond activation of the substrate, alkyne insertion, and intramolecular insertion of the CN Ts group into the CRu bond. Isotope-labeling experiments are performed to understand the underlying mechanism of the reaction.