Asymmetric epoxidation of chromenes catalyzed by chiral pyrrolidine SalenMn(III) complexes with an anchored functional group |
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Authors: | Xiang Zhang Dong‐Ping Wang Yin‐Bao Jia Xiao‐Bing Lu Hui Wang Li‐Cheng Sun |
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Institution: | 1. State Key Laboratory of Fine Chemicals, Dalian University of Technology, 116012 Dalian, People's Republic of China;2. KTH Chemistry, Organic Chemistry, Royal Institute of Technology, 10044 Stockholm, Sweden |
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Abstract: | Chiral pyrrolidine SalenMn(III) complexes with an anchored functional group at the Naza‐substituent in the pyrrolidine backbone were synthesized, and used as catalysts for asymmetric epoxidation of substituted chromenes. The complex 1 with an anchored imidazole as acceptor could effectively catalyze epoxidation of substituted chromenes in the absence of expensive additive 4‐phenyl pyridine N‐oxide (PPNO) by the coordination of the anchored organic base to the central manganese ion. Complexes 2 and 3 with a quaternary ammonium salt unit at the Naza‐substituent in the pyrrolidine backbone displayed higher activities than Jacobsen catalyst and the analogous complex 4 without anchored functional group in the aforementioned reaction. Copyright © 2008 John Wiley & Sons, Ltd. |
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Keywords: | pyrrolidine SalenMn(III) complexes asymmetric epoxidation chromene enantioselectivity |
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