Ru(II)-Catalyzed Reactions of <i>ortho</i>-Hydroxy Enaminones with Diazonaphthoquinones: Synthesis of Unsymmetrical Biaryl Diols

A Ru(II)-catalyzed method for constructing an unsymmetrical biaryl diol has been accomplished using <i>ortho</i>-hydroxy enaminone and diazonaphthoquinone. The reaction is simple, straighforward, and time-economic with a broad substrate scope. Our results and preliminary mechanistic studies reveal that the reaction proceeds via non-decarbonylative insertion of quinoid carbene to <i>ortho</i>-hydroxy enaminone based on C-C bond activation and subsequent migratory rearrangement. The developed method delivers monoprotected biaryl diol, naphtha benzofuran, and cyclophane skeleton.