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多官能镍-氢键-氮杂环翁催化剂促进的吲哚与硝基烯烃的立体选择性 1,4-加成反应。

Diastereodivergent Asymmetric 1,4-Addition of Oxindoles to Nitroolefins by Using Polyfunctional Nickel-Hydrogen-Bond-Azolium Catalysts.

机构信息

Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, 70569 Stuttgart (Germany).

出版信息

Angew Chem Int Ed Engl. 2015 Aug 24;54(35):10303-7. doi: 10.1002/anie.201502930. Epub 2015 Jun 26.

Abstract

Diastereodivergency is a challenge for catalytic asymmetric synthesis. For many reaction types, the generation of one diastereomer is inherently preferred, while the other diastereomers are not directly accessible with high efficiency and require circuitous synthetic approaches. Overwriting the inherent preference by means of a catalyst requires control over the spatial positions of both reaction partners. We report a novel polyfunctional catalyst type in which a Ni(II) -bis(phenoxyimine) unit, free hydroxy groups, and an axially chiral bisimidazolium entity participate in the stereocontrol of the direct 1,4-addition of oxindoles to nitroolefins. Both epimers of the 1,4-adduct are accessible in excess on demand by changes to the ligand constitution and configuration. As the products have been reported to be valuable precursors to indole alkaloids, this method should allow access to their epimeric derivatives.

摘要

非对映选择性是催化不对称合成面临的一个挑战。对于许多反应类型,一种非对映异构体的生成是固有偏好的,而其他非对映异构体则不能以高效率直接获得,需要迂回的合成方法。通过催化剂来覆盖固有偏好需要控制两个反应伙伴的空间位置。我们报告了一种新型多功能催化剂类型,其中 Ni(II)-双(苯氧基亚胺)单元、游离羟基和轴向手性双咪唑鎓实体参与了吲哚啉与硝基烯烃的直接 1,4-加成的立体控制。通过改变配体的结构和构型,可以按需获得过量的 1,4-加成物的两种差向异构体。由于这些产物被报道是吲哚生物碱的有价值前体,因此该方法应该可以获得它们的差向异构体衍生物。

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