Aerobic Baeyer-Villiger oxidation of cyclic ketones over periodic mesoporous silica Cu/Fe/Ni/Co-HMS-X

Baeyer-Villiger oxidation is important reaction in the organic synthesis for designing value added lactone/esters from the respective carbonyl compounds. Usually an active metal-containing material in the presence of peroxides catalyzes this reaction. Here highly ordered metal promoted periodic mesoporous silica with high surface area has been synthesized hydrothermally by the sol-gel method and thoroughly characterized by surface area and porosity measurements, SAXS, FESEM, HRTEM, FFIR, UV-Vis, NH3-TPD and XRD techniques. Liquid phase Baeyer-Villiger oxidation of ketones to the corresponding esters have been carried out using molecular oxygen as an oxidant, benzaldehyde as the sacrificing agent over Co-HMS-X and M-Co-HMS-X (metal = Ni, Fe, Cu) as catalysts. The obtained results demonstrate that among the three promoted catalyst, i.e. Ni-Co-HMS-X, Cu-Co-HMS-X and Fe-Co-HMS-X, Ni promoted catalyst is a promising and efficient catalyst with high catalytic activity (>99% cyclohexanone conversion and >99% epsilon-caprolactone selectivity) for the oxidation of cyclohexanone to epsilon-caprolactone. The high catalytic activity is attributed to the Ni on the wall of mesoporous silica along with cyclohexanone, which results in successful completion of the oxygen transfer step and generation of epsilon-caprolactone. Interesting information regarding cooperative role of cobalt and nickel towards catalytic activity is observed. (C) 2015 Elsevier B.V. All rights reserved.