Epoxidation of alkenes catalyzed by cobalt(II) calix[4]pyrrole

The new developed epoxidation system utilizing cobalt(II) calix[4]pyrrole as a catalyst in the aldehyde/oxygen as an oxidant was explored. Six calix[4]pyrrole ligands were synthesized and the well characterized ligands were complexed with Co(II) salts. It was disclosed that Co(II) meso-tetrakis (4-methoxyphenyl)-tetramethyl calix[4]pyrrole revealed the best catalytic performance to provide the corresponding epoxide in high yields with excellent selectivity under mild conditions. In addition, the stereoselectivity and regioselectivity studies of the system using cis- and trans-stilbenes and 4-vinylcyclohexene, as chemical probes were thoroughly investigated.