In this paper, we report the mechanochemical synthesis of unsymmetrical salens using grinding and ball milling technologies, respectively, both of which were afforded in good yield. The chelating effect of the unsymmetrical salens with zinc, copper, and cobalt was studied and the chiral Co–salen complex 2f was obtained in 98% yield. Hydrolytic kinetic resolution (HKR) of epichlorohydrin with water catalyzed by complex 2f (0.5 mol %) was explored and resulted in 98% ee, suggesting complex 2f could serve as an enantioselective catalyst for the asymmetric ring opening of terminal epoxides by phenols. A library of α-aryloxy alcohols 3 was thereafter synthesized in good yield and high ee using 2f via the phenolic KR of epichlorohydrin.
In this paper, we report the mechanochemical synthesis of unsymmetrical salens using grinding and ball milling technologies, respectively, both of which were afforded in good yield. The chelating effect of unsymmetrical salens with zinc, copper, and cobalt was studied and the chiral Co-salen complex (2f) yielded upto 98%. Hydrolytic kinetic resolution (HKR) of epichlorohydrin with water catalyzed by 2f was explored and resulted in 98% in ee, suggesting 2f could serve as an enantioselective catalyst for the asymmetric ring-opening of phenols to terminal epoxides. A library of α-aryloxy alcohols (3) was thereafter synthesized in good yield and great ee using 2f via the phenolic KR of epichlorohydrin.
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