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Indexed by:期刊论文

Date of Publication:2006-01-25

Journal:JOURNAL OF CATALYSIS

Included Journals:SCIE、EI

Volume:237

Issue:2

Page Number:248-254

ISSN No.:0021-9517

Key Words:asymmetric epoxidation; enantioselectivity; pyrrolidine; (salen)Mn(III) complex; unfunctionalized alkenes

Abstract:A series of chiral (pyrrolidine salen)Mn(III) complexes were synthesized front N-aza-substituted (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-3.4-diaminopyrrolidine salen ligands. High yields and comparable enantioselectivity relative to Jacobsen's catalyst were achieved in asymmetric epoxidation of styrene and chromenes using NaClO/PPNO and m-CPBA/NMO as the oxidant systems. Complexes 1-3, featuring a tertiary airline unit, displayed higher activity than complex 4, bearing ail amide unit and Jacobsen's catalyst in the NaClO/PPNO aqueous/organic biphasic system. The influence of CH3I on epoxidation of 6-nitro-2,2-dimethylchromene catalysed by 1-4 in the biphasic medium was Studied to explore the catalysts with built-in phase-transfer capability. The alkenes' access pathway is discussed on the basis of the steric effect of the N-aza-substituent in the pyrrolidine backbone of complexes 1-3 on the enantioselectivity of epoxidation. (c) 2005 Elsevier Inc. All rights reserved.