Macrocyclic Mn(III) salen complexes as recyclable catalyst for oxidative kinetic resolution of secondary alcohols
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- 作者：Prasanta Kumar Bera ; Nabin Ch. Maity ; Sayed H.R. Abdi ; Noor-ul H. Khan ; Rukhsana I. Kureshy ; Hari C. Bajaj
- 关键词：Oxidative kinetic resolution ; Chiral macrocyclic Mn(III) salen complexes ; Secondary alcohols ; Diacetoxyiodobenzene ; N-bromosuccinimide
- 刊名：Applied Catalysis A: General
- 出版年：2 October, 2013
- 年：2013
- 卷：467
- 期：Complete
- 页码：542-551
- 全文大小：2063 K
文摘
New macrocyclic chiral Mn(III) salen complexes (C1-C4) were synthesized and were used as catalysts for oxidative kinetic resolution (OKR) of secondary alcohols with diacetoxyiodobenzene (PhI(OAc)2) and N-bromosuccinimide (NBS), in biphasic dichloromethane: water solvent mixture. Good to excellent enantioselectivities were achieved with catalyst C2 for several secondary alcohols having different steric environment. In general with catalyst C2, NBS as a co-oxidant showed better enantioselectivity than PhI(OAc)2 in OKR. The catalyst C2 was easily retrieved from the reaction mixture by the addition of hexane and recycled seven times both with NBS and PhI(OAc)2 as co-oxidants without losing its performance. Based on the experimental results a mechanism for OKR of racemic 1-phenylethanol has been proposed where (R,R)-Mn-salen preferably binds with (S)-1-phenylethanol to give (R)-1-phenylethanol in excess at the end of the reaction.