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首页> 外文期刊>Chemistry: A European journal >Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Amino Acid Derived Rhodium Complexes: On the Origin of Enantioselectivity and Enantioswitchability
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Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Amino Acid Derived Rhodium Complexes: On the Origin of Enantioselectivity and Enantioswitchability

机译：氨基酸衍生的铑配合物催化的酮的不对称转移加氢：对映选择性和对映可转换性的起源

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摘要

Amino acid based thio- ACHTUNGTRENUNGamides, hydroxamic acids, and hydrazides have been evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2- propanol. Catalysts containing thio- ACHTUNGTRENUNGamide ligands derived from l-valine were found to selectively generate the product with an R configuration (95% ee), whereas the corresponding lvaline- based hydroxamic acids or hydrazides facilitated the formation of the (S)-alcohols (97 and 91% ee, respectively). The catalytic reduction was examined by performing a structure– activity correlation investigation with differently functionalized or substituted ligands and the results obtained indicate that the major difference between the thioamide and hydroxamic acid based catalysts is the coordination mode of the ligands. Kinetic experiments were performed and the rate constants for the reduction reactions were determined by using rhodium– arene catalysts derived from amino acid thioamide and hydroxamic acid ligands. The data obtained show that the thioamide-based catalyst systems demonstrate a pseudo-first-order dependence on the substrate, whereas pseudozero- order dependence was observed for the hydroxamic acid containing catalysts. Furthermore, the kinetic experiments revealed that the rate-limiting steps of the two catalytic systems differ. From the data obtained in the structure–activity correlation investigation and along with the kinetic investigation it was concluded that the enantioswitchable nature of the catalysts studied originates from different ligand coordination, which affects the ratelimiting step of the catalytic reduction reaction.
机译：基于氨基酸的硫代乙酰丙酮酰胺，异羟肟酸和酰肼已被评估为铑在2-丙醇中酮催化的酮的不对称转移氢化中的配体。发现含有衍生自l-缬氨酸的硫代ACHTUNGTRENUNG酰胺配体的催化剂选择性地生成R构型（95％ee）的产物，而相应的基于缬氨酸的异羟肟酸或酰肼则促进了（S）-醇的形成（97和91％ee）。通过对功能不同或取代的配体进行结构-活性相关性研究，研究了催化还原反应，所得结果表明，基于硫酰胺和异羟肟酸的催化剂之间的主要区别在于配体的配位方式。进行了动力学实验，并使用衍生自氨基酸硫代酰胺和异羟肟酸配体的铑-芳烃催化剂确定了还原反应的速率常数。所获得的数据表明，基于硫酰胺的催化剂体系对底物表现出假一阶依赖性，而对于含异羟肟酸的催化剂则观察到假零阶依赖性。此外，动力学实验表明两个催化体系的限速步骤不同。从在结构-活性相关研究中获得的数据以及动力学研究得出的结论是，所研究催化剂的对映可转换性质源自不同的配体配位，这影响了催化还原反应的限速步骤。

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