A polymer-supported diacetatobis(2-quinolylbenzimidazole)copper(II) complex as an efficient catalyst for oxidation of alcohols with tert-butyl hydroperoxide

Abstract

A polymer-supported diacetatobis(2-quinolylbenzimidazole)copper(II) complex [PS-(QBIM) 2 Cu(II)] was synthesized by functionalization of chloromethylated polystyrene cross-linked with 6.5 % divinyl benzene with 2-(2 0 -quinolyl)benzimidazole and subsequent treatment with Cu(OAc) 2 in methanol. The complex was characterized by physical, analytical and spectroscopic techniques. Electronic and ESR spectra, together with magnetic susceptibility measurements, indicated that the complex was paramagnetic with distorted octahedral geometry around the copper. The complex was found to be active toward oxidation of various alcohols including phenol, benzyl alcohol and cyclohexanol using 70 % aqueous tert-butyl hydroperoxide under mild conditions. Under the optimized reaction conditions, cyclohexanol gave 100 % conversion to cyclohexanone, benzyl alcohol gave 98 % yield of benzaldehyde and phenol gave 89 % yield of catechol and 4 % of hydroquinone. The complex was recycled five times without much loss in catalytic activity.

Magnetic nanoparticles entrapped in the cross-linked poly(imidazole/imidazolium) immobilized Cu(ii): an effective heterogeneous copper catalyst

“…[1][2][3][4] However, in recent years, heterogenization of copper has received considerable attention through supporting or immobilizing the catalyst into or onto the insoluble solid support. Some of the most important heterogeneous Cu-catalyzed processes reported in recent years, include self-condensation of amines, 5 C-H arylation, 6,7 asymmetric Henry reaction, 8,9 terminal alkyne homocoupling, 10,11 kinetic resolution of 1,2-diols, 12,13 Ulmann type C-X cross-coupling, [14][15][16] chemoselective hydrogenation of cinnamaldehyde, 17 Sonogashira reaction, 18,19 alcohol oxidation, 20 epoxidation of alkenes, 21,22 addition of terminal alkynes to imines, [23][24][25][26] and, perhaps the most important, Cu-azide-alkyne cycloaddition (CuAAC) reaction resulting in 1,2,3-triazoles known as a click reaction.…”