Chiral enhancement in the confined space of zeolites for the asymmetric synthesis of β-hydroxy nitroalkanes
作者:Noor-ul Hasan Khan、Mohd. Bismillah Ansari、Eko Adi Prasetyanto、Hailian Jin、Sang-Eon Park
DOI:10.1016/j.tetasy.2010.12.016
日期:2011.1
(1S,2S)-N-1,N-2-Bis(3-chlorobenzyl)cyclohexane-1,2-diamine 1a' and (1S,2S)-N-1,N-2-bis(4-chlorobenzyl) cyclohexane-1,2-diamine 1b' were used to prepare chiral Cu(II) complexes Cu-Y-1a, Cu-Y-1b, Cu-mZSM5-1a, and Cu-mZSM5-1b by a flexible ligand method using copper exchanged zeolite Y and mesoporous ZSM-5. The characterization of zeolite supported complexes was performed by microanalysis, IR-, diffuse reflectance spectroscopy (DRS), EPR spectroscopy, specific rotation and thermogravimetric analysis (TGA). The catalytic activity of these supported complexes was explored for the asymmetric nitroaldol reaction of various aldehydes with nitromethane at 0 degrees C. Excellent yields (up to 99%) of beta-hydroxy nitroalkane with an ee of up to 94% were achieved in the case of benzaldehyde as substrate. Significantly, the performance of the supported catalyst was better in terms of enantioselectivity than the complex under homogenous conditions. The supported catalysts were recycled four times with no observable loss in performance and no leaching of the catalytically active complex during the nitroaldol reaction. (C) 2010 Elsevier Ltd. All rights reserved.
采用柔性配体法,分别以(1S,2S)-N-1,N-2-双(3-氯苯甲基)环己烷-1,2-二胺1a'和(1S,2S)-N-1,N-2-双(4-氯苯甲基)环己烷-1,2-二胺1b'为配体,使用铜离子交换的沸石Y和介孔ZSM-5为载体,成功制备了手性铜(II)配合物Cu-Y-1a、Cu-Y-1b、Cu-mZSM5-1a和Cu-mZSM5-1b。通过微分析、红外光谱、漫反射光谱(DRS)、电子顺磁共振光谱(EPR)、比旋光度和热重分析(TGA)对沸石负载型配合物进行了表征。这些负载型配合物在0°C下用于各种醛与硝基甲烷的不对称硝基aldol反应的催化活性得到了研究。其中,以苯甲醛为底物时,获得了优异的收率(高达99%)的β-羟基硝基烷烃,其对映选择性高达94%。值得注意的是,与均相条件下的配合物相比,负载型催化剂在对映选择性方面表现更优。在硝基aldol反应过程中,负载型催化剂可循环使用四次,且未观察到催化活性组分的流失或催化活性的明显下降。©2010 Elsevier Ltd. 保留所有权利。