Asymmetric epoxidation of styrene and chromenes catalysed by chiral (salen)Mn(III) complexes with a pyrrolidine backbone

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• 作者：Dongping Wang ; Mei Wang ; Xiuna Wang ; Yonggang Chen ; Aiping Gao and Licheng Sun
• 关键词：Asymmetric epoxidation ; Enantioselectivity ; Pyrrolidine ; (Salen)Mn(III) complex ; Unfunctionalized alkenes
• 刊名：Journal of Catalysis
• 出版年：2006
• 出版时间：25 January 2006
• 年：2006
• 卷：237
• 期：2
• 页码：248-254
• 全文大小：141 K

文摘

A series of chiral (pyrrolidine salen)Mn(III) complexes were synthesized from lick to view the MathML source"">N_aza-substituted (lick to view the MathML source"">R,R)-lick to view the MathML source"">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 amine unit, displayed higher activity than complex 4, bearing an 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 lick to view the MathML source"">N_aza-substituent in the pyrrolidine backbone of complexes 1–3 on the enantioselectivity of epoxidation.