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论文类型：期刊论文

发表时间：2007-06-01

发表刊物：JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

收录刊物：SCIE

卷号：270

期号：1-2

页面范围：278-283

ISSN号：1381-1169

关键字：asymmetric epoxidation; chiral pyrrolidine; chromene; pyridinium salt; (salen)Mn(III) complex

摘要：Chiral (pyrrolidine salen)Mn(III) complexes 1 with an N-benzoyl group and 2 with an N-isonicotinoyl group as well as the corresponding N-methyl (3) and N-benzyl (4) pyridinium salts of 2 were synthesized. The catalytic properties of 1-4 and 2 with excess CH3I were explored to figure out the influence of the internal pyridinium salt in the catalyst on asymmetric epoxidation of substituted chromenes with NaClO/PPNO as an oxidant system in the aqueous/organic biphasic medium. The (pyrrolidine salen)Mn(III) complexes with an internal pyridinium salt, either formed in situ or isolated, displayed higher activities than analogous complexes 1, 2 and Jacobsen's catalyst in the aforementioned reaction, with comparable high yields and ee values. The acceleration of the reaction rate is attributed to the phase transfer capability of the built-in pyridinium salt of the (salen)Mn(III) catalyst. The effect of the internal pyridinium salt on the epoxidation of substituted chromenes is similar to that of the external pyridinium salts and ammonium halides. (c) 2007 Elsevier B.V. All rights reserved.