Influence of Halide Ion and Lewis Acid in the Demetalation of a Spirolactam Cyclohexadienyl Ruthenium Complex

Demetalation of an electron-rich spirolactam-based (cyclohexadienyl)Ru(II) complex is achieved upon treatment with boron trifluoride and a source of chloride ion. The cyclohexadienyl ligand is converted to a cyclohexadienone, cyclohexenone, or cyclohexenone epoxide derivative as a function of the specific reaction conditions. Stable (cyclohexadienyl)ruthenium substrates potentially suitable for demetalation under these conditions are prepared via intramolecular spirocyclization of (η6-arene)Ru precursors; thus, demetalation completes a net Ru-mediated dearomatization sequence. Moreover, the functionalized spirolactam products obtained are structurally distinct from those produced via direct oxidative demetalation.