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首页> 外文期刊>Catalysis science & technology >Chitosan as a chiral ligand and organocatalyst: preparation conditions-property-catalytic performance relationships
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Chitosan as a chiral ligand and organocatalyst: preparation conditions-property-catalytic performance relationships

机译：壳聚糖作为手性配体和organocatalyst:准备conditions-property-catalytic性能的关系

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Chitosan is an abundant and renewable chirality source of natural origin. The effect of the preparation conditions by alkaline hydrolysis of chitin on the properties of chitosan was studied. The materials obtained were used as ligands in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic prochiral ketones and oxidative kinetic resolution of benzylic alcohols as well as organocatalysts in the Michael addition of isobutyraldehyde to N-substituted maleimides. The degrees of deacetylation of the prepared materials were determined by H-1 NMR, FT-IR and UV-vis spectroscopy, the molecular weights by viscosity measurements, their crystallinity by WAXRD, and their morphology by SEM and TEM investigations. The materials were also characterized by Raman spectroscopy. The biopolymers which have molecular weights in a narrow (200-230 kDa) range and appropriate (80-95%) degrees of deacetylation were the most efficient ligands in the enantioselective transfer hydrogenation, whereas in the oxidative kinetic resolution the activity of the complexes and the stereoselectivity increased with the degree of deacetylation. The chirality of the chitosan was sufficient to obtain enantioselection in the Michael addition of isobutyraldehyde to maleimides in the aqueous phase. Interestingly, the biopolymer afforded the opposite enantiomer in excess compared to the monomer, d-glucosamine. In this reaction, good correlation between the degree of deacetylation and the catalytic activity was found. These results are novel steps in the application of this natural, biocompatible and biodegradable polymer in developing environmentally benign methods for the production of optically pure fine chemicals.
机译：壳聚糖是一种丰富、可再生的手性源的天然来源。通过碱性水解制备条件甲壳素壳聚糖的性质进行了研究。作为配体在获得的材料ruthenium-catalysed不对称转移氢化芳香的前手性的酮苄基的醇的氧化动力学拆分以及organocatalysts迈克尔除了isobutyraldehyde n马来酰亚胺。h - NMR测定准备材料,红外光谱和紫外可见光谱,分子权重的粘度测量,他们结晶度由WAXRD及其形态SEM和TEM调查。也拉曼光谱的特征。生物聚合物的分子量窄(200 - 230 kDa)和适当的范围(80 - 95%)程度的脱乙酰作用是最高效的配体的拆分转移氢化,而氧化动力学分辨率复合物的活动和立体选择性增加程度的脱乙酰作用。壳聚糖是足以获得enantioselection迈克尔加成的isobutyraldehyde马来酰亚胺的水溶液阶段。相反的对映体过量相比单体,d-glucosamine。脱乙酰作用的程度之间的相关性和催化活性。结果新颖的应用程序的步骤这种自然、生物相容性和生物降解的聚合物在发展中对环境无害生产光学纯的好方法化学物质。

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