Selective epoxidation of alkenes catalyzed by cobalt complexes

Abstract

The elective epoxidation of alkenes catalyzed by cobalt complexes in the presence of 2-ethylbutyraldehyde/O₂ was examined. Cyclohexene was utilized as a chemical model and cyclohexen oxide was acquired as a major product with high yield and excellent selectivity. The parameters that had a major influence on the raction included type of ligands and solvent. The utilization of cobalt(II) complexes of calix[4]pyrrole 10 and thiophen-o-phen 12 was disclosed to be appropriate catalysts for alkene epoxidation. In addition, the stereoselectivity and regioselectivity studies of the system using cis- and trans-stilbenes and 4-vinylcyclohexene, respectively as chemical probes were thoroughly investigated. The isolation of 2-ethylbutaonic acid as a by-product of the reaction was clearly provided informative clue for the mechanism of this reaction to take place via peroxy acid and free radical process.