Regioselective C-H Bond Cleavage/Alkyne Insertion under Ruthenium Catalysis

The ruthenium-catalyzed coupling reactions of benzamides with alkynes in the presence of acetic acid as a promoter smoothly proceeded regio- and stereoselectively through a directed C-H bond cleavage to produce the corresponding ortho-alkenylated products. Phenylpyrazoles and related substrates also underwent a similar coupling to give dialkenylated products selectively. Several competitive experiments were performed to obtain mechanistic insight into both the mono- and dialkenylation reactions.