Combustion-Synthesized Porous CuO-CeO2-SiO2 Composites as Solid Catalysts for the Alkenylation of C(sp3)-H Bonds Adjacent to a Heteroatom via Cross-Dehydrogenative Coupling

Abstract

A series of mixed oxides of CuO, CeO2, and SiO2 were prepared by gel combustion and employed for the first time as efficient solid catalysts in a solvent-less liquid-phase cross-dehydrogenative coupling. The facile one-pot catalyst synthesis resulted in highly porous materials presenting large specific surface areas and strong metal–support interactions. The interaction with highly dispersed CeO2 enhanced the redox properties of the CuO species. The CuO-CeO2-SiO2 composites exhibited excellent catalytic performance for the selective coupling between 1,1-diphenylethylene and tetrahydrofuran with a yield up to 85% of 2-(2,2-diphenylvinyl)-tetrahydrofuran in the presence of di-tert-butyl peroxide (DTPB) and KI. Albeit both CuO and CeO2 species are proved to be responsible for the catalytic conversion, a great synergistic improvement in the catalytic activity was obtained by extended contact between the oxide phases by high porosity in comparison with the reactions using individual Cu or Ce catalysts. The activity of the composite catalyst was shown to be highly stable after five successive reaction cycles. Furthermore, the study scope was extended to the synthesis of different derivatives via composite-catalyzed coupling of C(sp2)-H with C(sp3-H) adjacent to a heteroatom. The good yields recorded proved the general validity of this composite for the cross-dehydrogenative coupling reaction rarely performed on solid catalysts.