Transition Metal Complexes of Diazenes XXXVI [1a]: Formation of Indoles from Azobenzene and Diphenylacetylene through Supported Aqueous Phase Catalysis by Rhodium(I) Complexes

Article abstract of DOI:10.1007/BF00807071

A SiO₂ supported Rh(I) catalyst of trisulfonated triphenylphosphine catalyzes the addition of diphenylacetylene to azobenzene in refluxing butanol in the presence of triphenylphosphine to afford N-anilino-2,3-diphenylindole and 2,3-diphenylindole with turnover numbers of 80 and 20, respectively. As compared to the known homogeneous or heterogeneous (SiO₂) catalysis by RhCl(PPh₃)₃, the supported aqueous phase system retains a constant turnover frequency throughout the reaction and can be partially recycled.