Directed <i>ortho</i>-C–H Silylation Coupled with <i>trans</i>-Selective Hydrogenation of Arylalkynes Catalyzed by Ruthenium Complexes of a Xanthene-Based <i>Si,O,Si</i>-Chelate Ligand, “Xantsil”

Ruthenium complexes bearing a xanthene-based bis­(silyl) chelate ligand, “xantsil” ((9,9-dimethylxanthene-4,5-diyl)­bis­(dimethylsilyl)), Ru­{κ³(<i>Si,O,Si</i>)-xantsil}­(CO)­(PR₃) (<b>1-Cy</b>: R = Cy (cyclohexyl), <b>1-Cyp</b>: R = Cyp (cyclopentyl)), were found to catalyze the reactions of internal arylalkynes with tertiary silanes (1–1.3 equiv) at a moderate temperature (room temperature to 70 °C) to give (<i>E</i>)-alkenes having an <i>ortho</i>-silylated aryl group, i.e., (<i>E</i>)-R¹C­(H)C­(H)­(C₆H₃-<i>o</i>-SiR³₃-<i>p</i>-R²). These catalytic reactions involve a unique <i>ortho</i>-selective C–H silylation of an aryl group in arylalkynes accompanied by hydrogenation of their C–C triple bonds (<i>ortho</i>-C–H silylation/hydrogenation). Importantly, in these reactions, the alkynyl moiety of arylalkynes serves as both a directing group and a hydrogen acceptor. The substrate scope of this <i>ortho</i>-C–H silylation/hydrogenation was explored by use of eight combinations of arylalkynes and tertiary silanes. In cases using bulky substrates, the catalytic performance of <b>1-Cyp</b> with a relatively less bulky phosphine ligand (PCyp₃) was shown to be superior to that of the PCy₃ analogue <b>1-Cy</b>

Directed <i>ortho</i>-C–H Silylation Coupled with <i>trans</i>-Selective Hydrogenation of Arylalkynes Catalyzed by Ruthenium Complexes of a Xanthene-Based <i>Si,O,Si</i>-Chelate Ligand, “Xantsil”

Ruthenium complexes bearing a xanthene-based bis­(silyl) chelate ligand, “xantsil” ((9,9-dimethylxanthene-4,5-diyl)­bis­(dimethylsilyl)), Ru­{κ³(<i>Si,O,Si</i>)-xantsil}­(CO)­(PR₃) (<b>1-Cy</b>: R = Cy (cyclohexyl), <b>1-Cyp</b>: R = Cyp (cyclopentyl)), were found to catalyze the reactions of internal arylalkynes with tertiary silanes (1–1.3 equiv) at a moderate temperature (room temperature to 70 °C) to give (<i>E</i>)-alkenes having an <i>ortho</i>-silylated aryl group, i.e., (<i>E</i>)-R¹C­(H)C­(H)­(C₆H₃-<i>o</i>-SiR³₃-<i>p</i>-R²). These catalytic reactions involve a unique <i>ortho</i>-selective C–H silylation of an aryl group in arylalkynes accompanied by hydrogenation of their C–C triple bonds (<i>ortho</i>-C–H silylation/hydrogenation). Importantly, in these reactions, the alkynyl moiety of arylalkynes serves as both a directing group and a hydrogen acceptor. The substrate scope of this <i>ortho</i>-C–H silylation/hydrogenation was explored by use of eight combinations of arylalkynes and tertiary silanes. In cases using bulky substrates, the catalytic performance of <b>1-Cyp</b> with a relatively less bulky phosphine ligand (PCyp₃) was shown to be superior to that of the PCy₃ analogue <b>1-Cy</b>