THE SYNTHESIS OF AN UNSYMMETRICAL SALEN-TYPE LIGAND AND ITS COBALT COMPLEX AS AN EFFICIENT CATALYST FOR THE HYDROLYTIC KINETIC RESOLUTION OF EPICHLOROHYDRIN

Abstract

An unsymmetrical salen-type ligand, (R,R)-N-(3,5-di-tert-butylsalicylidene)-N’-[3-tert-butyl-5-(4-vinylphenyl)salicylidene]cyclohexane-1,2-diamine, was readily synthesized using the condensation of (R,R)-cyclohexane-1,2-diamine with 3,5-di-tert-butyl-2-hydroxybenzaldehyde and 3-tert-butyl-2-hydroxy-5-(4-vinylphenyl)benzaldehyde in an isolated yield of 80%. The ligand was characterized using ¹H and ¹³C NMR, MS and HRMS, elemental analysis. The corresponding cobalt (II) complex was subsequently prepared and characterized using HRMS and elemental analysis. It was observed that the salen-type cobalt complex exhibited excellent activity and selectivity in the hydrolytic kinetic resolution of racemic mixture of epichlorohydrin, with more than 99% ee and 53% conversion being achieved within 2 h at the catalyst loading of 0.5 mol%.