Methyl Iodide Accelerated Asymmetric Epoxidation of Alkenes Catalyzed by Chiral Salen-Mn（Ⅲ） Complexes with Tertiary Amine Units  

作　　者：孙杨 唐宁 

机构地区：[1]College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000, China

出　　处：《Chinese Journal of Chemistry》2007年第5期674-678,共5页中国化学（英文版）

基　　金：Project supported by the National Natural Science Founclation of China （No. 20571035）, the Gansu Natural Science Foundation of China （No. 3ZS051-A25-003）.Acknowledgement The authors are grateful to the Instrumental Analysis and Research Center of Lanzhou University and State Key Laboratory of Applied 0rganic Chemistry for providing instrumentation facilities.

摘　　要：A series of chiral salen-Mn（Ⅲ） complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-dimethylpyridine N-oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH2Cl2/H2O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI-HRMS analysis revealed the formation of a novel （salen）manganese（m） intermediate featuring two quaternary ammonium units, and bearing a pyridine N-oxide and a molecule of water simultaneously axially-coordinated backbone.A series of chiral salen-Mn（Ⅲ） complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-dimethylpyridine N-oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH2Cl2/H2O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI-HRMS analysis revealed the formation of a novel （salen）manganese（m） intermediate featuring two quaternary ammonium units, and bearing a pyridine N-oxide and a molecule of water simultaneously axially-coordinated backbone.

关 键 词：asymmetric epoxidation ENANTIOSELECTIVITY unfunctionalized alkene BIPHASIC PHASE-TRANSFER 

分 类 号：O623.12[理学—有机化学]