Probing Catalyst Function - Electronic Modulation of Chiral Polyborate Anionic Catalysts.
Probing Catalyst Function - Electronic Modulation of Chiral Polyborate Anionic Catalysts.
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DOI：
10.1021/acs.joc.1c01769
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发表时间：
2021-12-17
影响因子：
3.6
通讯作者：
Wulff, William D.
中科院分区：
文献类型：
--
作者：
Osminski, Wynter E. G.;Lu, Zhenjie;Zhao, Wenjun;Mohammadlou, Aliakbar;Yin, Xiaopeng;Matthews, Emily C.;Canestraight, Virginia M.;Staples, Richard J.;Allen, Connor J.;Hirschi, Jennifer S.;Wulff, William D.
VAPOL和VANOL的硼氧酸盐络合物是一种手性阴离子平台，可用作不对称催化的多功能分级竞技场。该平台的结构基础是一个手性聚硼酸酯核心，共价连接在一起的醇（或酚）和拱形联芳基配体。该多硼酸盐平台通过反应底物原位组装，因此可以从各种醇（或酚）和双酚配体快速组装多种手性催化剂用于筛选催化剂活性。在本研究中，在空间和电子性质的硼氧烷催化剂的苯酚/醇组分的变化进行了探讨，以揭示其对催化不对称氮杂环丙烷化反应中的不对称诱导的影响。Hammett研究与其中两种底物在对映体步骤中氢键键合到硼氧烷核心的机制一致。Hammett研究的结果得到了计算研究的支持，其中发现质子化亚胺氢键键合到阴离子硼氧烷核心的H-O距离随着并入硼氧烷的苯酚单元的电子释放能力的增加而减小。结果与硼氧烷酸盐催化剂作为刘易斯酸起作用并通过刘易斯酸/刘易斯碱相互作用活化亚胺的机理不一致。
Boroxinate complexes of VAPOL and VANOL are a chiral anionic platform that can serve as a versatile staging arena for asymmetric catalysis. The structural underpinning of the platform is a chiral polyborate core that covalently links together alcohols (or phenols) and vaulted biaryl ligands. The polyborate platform is assembled in situ by the substrate of the reaction, and thus a multiplex of chiral catalysts can be rapidly assembled from various alcohols (or phenols) and bis-phenol ligands for screening of catalyst activity. In the present study, variations in the steric and electronic properties of the phenol/alcohol component of the boroxinate catalyst are probed to reveal their effects on the asymmetric induction in the catalytic asymmetric aziridination reaction. A Hammett study is consistent with a mechanism in which the two substrates are hydrogen-bonded to the boroxinate core in the enantiogenic step. The results of the Hammett study are supported by a computational study in which it is found that the H–O distance of the protonated imine hydrogen bonded to the anionic boroxinate core decreases with an increase in the electron releasing ability of the phenol unit incorporated into the boroxinate. The results are not consistent with a mechanism in which the boroxinate catalyst functions as a Lewis acid and activates the imine by a Lewis acid/Lewis base interaction.
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影响因子：
15
作者：
Hu, Gang;Gupta, Anil K.;Wulff, William D.
通讯作者：
Wulff, William D.
影响因子：
15
作者：
Vetticatt, Mathew J.;Desai, Aman A.;Wulff, William D.
通讯作者：
Wulff, William D.
影响因子：
4.3
作者：
Zhang, Yu;Desai, Aman;Wulff, William D.
通讯作者：
Wulff, William D.
DOI：
10.1039/p29910001541
发表时间：
1991-10-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
影响因子：
--
作者：
DEAN, C;WHITTAKER, D
通讯作者：
WHITTAKER, D
影响因子：
16.6
作者：
Seguin, Trevor J.;Wheeler, Steven E.
通讯作者：
Wheeler, Steven E.