Metal Ion-Planted MCM-41: 2. Catalytic Epoxidation of Stilbene and Its Derivatives withtert-Butyl Hydroperoxide on Mn-MCM-41

Abstract

Manganese ion-planted MCM-41 (Mn-MCM-41) prepared by the template ion-exchange (TIE) method has been found to be active for catalytic epoxidation of aromatic olefins. The activity of Mn-MCM-41 was the greatest among those of Mn/MCM-41, Mn/SiO2, Mn/Al2O3, which were prepared by a conventional impregnation method, and Mn-ZSM-5 prepared by an ion-exchange method. The proper reaction conditions have first been determined fortrans-stilbene as the substrate. The most effective oxidant wastert-butyl hydroperoxide (TBHP) at 328–348 K among H2O2, PhIO, TBHP, and O2. The highest yield of 93% oftrans-stilbene oxide was obtained by using a mixed solvent of acetonitrile and dimethylformamide of 9:1 (v/v) at 328 K. Mn-MCM-41 could be used repeatedly for the reaction without decrease in the catalytic activity. The epoxidation oftransandcisisomers of various aromatic olefins has then been studied. The oxidation of olefins having bulky substituents such as 4-tert-butylphenyl and 2-naphthyl could proceed in the mesopores of Mn-MCM-41. The epoxidation oftransisomers was easier than that ofcisisomers. The olefins withcisconfiguration all gave the correspondingtransoxides with small amounts oftransolefins as by-products. A radical mechanism has been suggested for the oxidation on the basis of the product distributions.