Approach to the Synthesis of Dimeric Salen-Co(Ⅲ):A Recoverable Catalyst for Rac-Eprichlorohydrin HKR

The synthesis of chiral dimeric Salen ligand 5,5′-methylene-di-(R,R)-N-(3-tert-butylsalicylidine)-N′-(3′,5′-di-tert-butylsalicylidene)-1,2-cyclohexanediamine which using 2-tert-butylphenol as starting material is reported. This compound reacts with cobalt (Ⅱ) acetate and then oxidized by air to give dimeric Salen catalyst 5 in this paper, which catalyzes the hydrolytic kinetic resolution (HKR) of racemic epichlorohydrin to afford biologically important chiral epoxides and diols. Ee values of diol up to 97% were obtained, and the catalyst was recovered with no apparent loss.