Photo-Organocatalytic Enantioselective Radical Cascade Enabled by Single-Electron Transfer Activation of Allenes
Photo-Organocatalytic Enantioselective Radical Cascade Enabled by Single-Electron Transfer Activation of Allenes
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DOI：
10.1002/adsc.201900973
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发表时间：
2019-11-18
影响因子：
5.4
通讯作者：
Melchiorre, Paolo
中科院分区：
文献类型：
--
作者：
Alessandro Perego, Luca;Bonilla, Pablo;Melchiorre, Paolo
联烯通常用于金属介导的转化、环加成反应和自由基过程。然而，它们通过单电子转移（SET）的活化在很大程度上还未被探索。在此，我们报告了一个可见光驱动的对映选择性有机催化过程，利用激发态反应的手性亚胺离子激活联烯SET氧化。随后的丙二烯阳离子自由基参与立体控制的级联反应，以提供具有良好的对映体选择性和精致的非对映体选择性的手性双环支架。密度泛函理论（DFT）计算支持的机制，结合特殊的化学联烯自由基阳离子与极性反应。
Allenes are commonly used in metal-mediated transformations, cycloaddition reactions, and radical processes. However, their activation by single-electron transfer (SET) is largely underexplored. Herein, we report a visible light-driven enantioselective organocatalytic process that uses the excited-state reactivity of chiral iminium ions to activate allenes by SET oxidation. The ensuing allene cation radicals participate in stereocontrolled cascade reactions to deliver chiral bicyclic scaffolds with good enantioselectivity and exquisite diastereoselectivity. Density Functional Theory (DFT) calculations support a mechanism that combines the peculiar chemistry of allene radical cations with polar reactivity.