Iron chloride supported on pyridine-modified mesoporous silica: an efficient and reusable catalyst for the allylic oxidation of olefins with molecular oxygen

A novel heterogeneous catalyst with iron chloride immobilized on pyridine-modified mesoporous silica has been developed. The supported Fe(III)/SiO2 catalyst displayed excellent catalytic properties for the allylic oxidation of 3,5,5-trimethylcyclohex-3-en-1-one (β-IP, 1) to 3,5,5-trimethlycyclohex-2-ene-1,4-dione (KIP, 2) with molecular oxygen as the oxidant under mild conditions. It can also catalyze the oxidation of other olefins, such as α-pinene and cyclohexene and its derivatives efficiently and selectively. In addition, the supported catalyst can be easily recycled without significant loss of activity and selectivity, which is a green alternative for practical applications.