Copper(II)-Catalyzed Asymmetric Photoredox Reactions: Enantioselective Alkylation of Imines Driven by Visible Light
Copper(II)-Catalyzed Asymmetric Photoredox Reactions: Enantioselective Alkylation of Imines Driven by Visible Light
复制标题
铜(II)催化的不对称光氧化还原反应：可见光驱动的亚胺对映选择性烷基化
DOI：
10.1021/jacs.8b09251
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发表时间：
2018-11-21
影响因子：
15
通讯作者：
Gong, Lei
中科院分区：
文献类型：
--
作者：
Li, Yanjun;Zhou, Kexu;Gong, Lei
不对称光氧化还原催化为通过新颖的反应途径开发手性分子的新合成方法提供了令人兴奋的机会。然而，使用第一行过渡金属配合物作为手性光氧化还原催化剂仍然是一个艰巨的挑战，尽管这些配合物经济、环境友好，并且通常表现出特殊的反应活性。我们在本文中报道了基于铜（II）双恶唑啉络合物（Cu-II-BOX）的一类高效不对称/光氧化还原双功能催化剂的开发，用于光诱导的亚胺对映选择性烷基化。该反应在非常温和的条件下进行，不需要任何其他光敏剂。简单的催化系统和易于调节的手性配体使得具有四取代碳立构中心的手性胺产物的形成具有显着高水平的对映选择性（36个实例，高达98% ee）。总体而言，Cu-II-BOX 催化剂引发自由基生成，并控制随后的立体选择性转化。该策略利用由第一行过渡金属和柔性手性配体组成的手性配合物作为不对称光氧化还原催化剂，为开发绿色不对称合成方法提供了有效的平台。
Asymmetric photoredox catalysis offers exciting opportunities to develop new synthetic approaches to chiral molecules through novel reaction pathways. Employing the first-row transition metal complexes as the chiral photoredox catalysts remains, however, a formidable challenge, although these complexes are economic, environmentally friendly, and often exhibit special reactivities. We report in this Article the development of one class of highly efficient asymmetric/ photoredox bifunctional catalysts based on the copper(II) bisoxazoline complexes (Cu-II-BOX) for the light-induced enantioselective alkylation of imines. The reactions proceed under very mild conditions and without a need for any other photosensitizer. The simple catalytic system and readily tunable chiral ligands enable a significantly high level of enantioselectivity for the formation of chiral amine products bearing a tetrasubstituted carbon stereocenter (36 examples, up to 98% ee). Overall, the Cu-II-BOX catalysts initiate the radical generation, and also govern the subsequent stereoselective transformations. This strategy utilizing chiral complexes comprised of a first-row transition metal and a flexible chiral ligand as the asymmetric photoredox catalysts provides an effective platform for the development of green asymmetric synthetic methods.