Olefin dihydroxylation mediated by Os-Zn-Al hydrotalcite-like catalyst: The scope and reactivity using various co-oxidants

Abstract

The heterogeneous oxidation of olefins to vicinal diols was investigated using an Os-Zn-Al hydrotalcite-like catalyst (HTlc). The Os-Zn-Al HTlc was synthesised by the co-precipitation method and characterised fully using XRD, FT-IR, TEM, SEM, ICP-OES and BET surface area measurements. The ability of the synthesised Os-Zn-Al HTlc to catalytically dihydroxylate olefins to vicinal diols using various co-oxidants (air, NMO, K3Fe(CN)6, H2O2 and t-BuOOH) was investigated. The focus was mostly on N-methylmorpholine N-oxide (NMO) and K3Fe(CN)6 since they are well established co-oxidants for osmium catalysed dihydroxylation. When NMO was used, 100 % olefin conversion was achieved for all olefins tested. While, 100% conversion was only achieved with electron rich olefins when K3Fe(CN)6 was used as co-oxidant. Recyclability and leaching tests were done, and it was found that the catalyst could be recycled at least 3 times in the NMO system and the K3Fe(CN)6-K2CO3 system was found to be truly heterogeneous.