“Twin-coronet” porphyrins bearing optically active 1,1′-bitetrahydronaphthalene derivatives on the both faces of the porphyrin were prepared as enantioselective oxidation catalysts modeling on cytochrome P-450s. The eclipsed isomer of the corresponding iron(III) porphyrins catalyzed epoxidation of styrenes substituted with electron-withdrawing groups in high e.e. (61–89%) and high product selectivity
在卟啉的两个面上带有光学活性 1,1'-双四氢萘衍生物的“双冠”卟啉被制备为模拟细胞色素 P-450 的对映选择性氧化催化剂。相应的铁 (III) 卟啉的失色异构体在高 ee (61–89%) 和高产物选择性下催化被吸电子基团取代的苯乙烯的环氧化。
Highly Selective Hydrolytic Kinetic Resolution of Terminal Epoxides Catalyzed by Chiral (salen)Co<sup>III</sup> Complexes. Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols
作者:Scott E. Schaus、Bridget D. Brandes、Jay F. Larrow、Makoto Tokunaga、Karl B. Hansen、Alexandra E. Gould、Michael E. Furrow、Eric N. Jacobsen
DOI:10.1021/ja016737l
日期:2002.2.1
The hydrolytickineticresolution (HKR) of terminal epoxides catalyzed by chiral (salen)Co(III) complex 1 x OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several
Enantioselective epoxidations of alkenes (12 examples) were achieved using a Shi-type carbohydrate-derived hydrate and Oxone. The chiral platform provided by the catalyst tolerates a wide range of substituents providing high yields and enantioselectivities (80-95.5% ee). However, styrene derivatives were only converted with poor selectivities (11-26% ee).
Catalytic and asymmetric epoxidation of styrenes and related aryl substituted olefins with the iron complexes of chiral bitetralin (Bitet)–linked “twin–coronet” porphyrins was performed with iodosylbenzene as an oxidant. Among two topological isomers of the catalyst, the eclipsed one (5b) showed higher enantioselectivity than the staggered (6b). With 5b, the resulting epoxides, except for the olefins bearing an electron–donating substituent, were obtained in good to excellent enantioselectivity (54—96% ee), especially for the styrenes with electron–withdrawing substituent(s). Being different from other porphyrin–based chiral catalysts, the catalyst 5b is robust enough under the applied oxidation conditions to exhibit chiral epoxidation with the same ee and the same rate as those of the initial period of the reaction even after about 500 turnovers. The Bitet catalyst is superior in the epoxide enantioselectivity than the corresponding chiral binaphthalene (Binap)–linked catalyst (3b). In the reactions with the catalysts 3b and 5b, good correlation in epoxide ees was observed. Increase of the epoxide ee in the reaction with the Bitet catalyst was elucidated by the shape and size of the reaction cavities of the Bitet were tighter than those of the latter. The observed ees of the substituted styrene oxides showed good correlation with Σσ+ values of their substituent(s). In the reaction with the electron–deficient olefins, π–π* interaction between the HOMO of the electron–rich Bitet auxiliary ring and the LUMO of the electron–deficient aryl ring of the substrate are pointed out as the key for the realization of high ees. Some nitrostyrenes, however, gave rather lower ees in spite of rather higher degree of their electron deficiency. This deviation was elucidated by the mismatching of their frontier orbitals.
The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
作者:Mattia Riccardo Monaco、Daniele Fazzi、Nobuya Tsuji、Markus Leutzsch、Saihu Liao、Walter Thiel、Benjamin List
DOI:10.1021/jacs.6b09179
日期:2016.11.9
The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Brønsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular
磷酸催化剂和羧酸之间的异二聚化自组装最近已被确立为布朗斯台德酸催化中的一种新活化模式。在本文中,我们对该激活原理进行了全面的机理研究,最终对其进行了阐明。报告了详细的研究,包括对超分子异二聚体的计算研究、催化循环的动力学研究,以及通过 DFT 计算对过渡态进行彻底分析,以合理化催化剂结构 - 选择性关系。在这些研究的基础上,我们开发了外消旋环氧化物的动力学拆分,其具有高选择性(高达 s = 93),以高对映纯度提供未反应的环氧化物和相应的受保护的 1,2-二醇。而且,