Carbonylation of cyclohexene to 2-cyclohexene-1-one by montmorillonite-supported Co(II) catalysts

Abstract

A novel environmentally-friendly catalytic system for the carbonylation of cyclohexene with molecular oxygen under conditions of mild temperature, and under an atmospheric oxygen pressure is presented. In this system, a series of readily-prepared cobalt complexes of 2-aminophenol and its derivatives immobilised onto montmorillonite were used as catalysts. The catalysts were characterised by FT-IR, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, diffuse reflectance ultraviolet visible spectra, scanning electron microscopic measurements, transmission electron microscopic measurements and the Brunauer-Emmett-Teller method. The effects of various reaction conditions such as catalyst dosage, temperature and time were optimised, obtaining an 88.7 % conversion with 72.0 % selectivity of 2-cyclohexene-1-one in 6 h. The results show that the catalytic activity of the cobalt complexes encapsulated in montmorillonite is higher than those of the free complexes. In addition, the heterogeneous catalysts were stable and can be recycled up to five times without any noticeable change in the catalytic activity.

Manganese(II) complexes with Bn-tpen as powerful catalysts of cyclohexene oxidation

“…Cyclohexene was used as a substrate, because it is very good model compound, it contains a single C–H bond and a double C=C bond, both of which can be an object of oxidation by high-valent manganese complexes and it was proved that it is a good starting point to better understand the mechanism of the reaction of more complex molecular entities, for example, the terpene ozonolysis (Nøjgaard et al 2007 ). It is also known, that the selective oxidation of unreactive C–H bonds of organic compounds is a crucial stage of catalysis (Gao et al 2015 ; Peng et al 2016 ). The exact knowledge of the mechanism of its oxidations may contribute to understanding of the processes occurring in living organisms (e.g., action of enzymes and oxygen toxicity), or in technological processes.…”