Light-Driven N-Heterocyclic Carbene Catalysis Using Alkylborates
Light-Driven N-Heterocyclic Carbene Catalysis Using Alkylborates
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DOI：
10.1021/acscatal.1c04153
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发表时间：
2021-10
期刊：
影响因子：
12.9
通讯作者：
Y. Sato;Yamato Goto;Kei Nakamura;Yusuke Miyamoto;Yuto Sumida;H. Ohmiya
中科院分区：
文献类型：
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作者：
Y. Sato;Yamato Goto;Kei Nakamura;Yusuke Miyamoto;Yuto Sumida;H. Ohmiya
自由基-自由基偶联是两种不同自由基物种之间的选择性反应，它为连接大体积单元的方法学做出了贡献。光驱动的N-杂环卡宾（NHC）有机催化被认为是实现自由基-自由基偶联的最先进的方法。催化过程包括由NHC催化剂和酰基供体形成酰基唑中间体，然后对该关键中间体进行单电子还原，这在很大程度上取决于光氧化还原催化剂。我们设计了一种自由基NHC催化，其中硼酸盐的直接光激发形成高还原剂促进了单电子还原事件。硼酸盐产生用于单电子转移过程的烷基自由基以完成自由基-自由基偶联。该方案除了使烯烃与烷基硼酸酯和酰基咪唑的自由基中继型烷基酰化之外，还使烷基硼酸酯和酰基咪唑之间的交叉偶联成为可能，从而提供具有宽范围的酮。
Radical–radical coupling, the selective reaction between two different radical species, has contributed to the methodology for connecting bulky units. Light-drivenN-heterocyclic carbene (NHC) organocatalysis is recognized as a state-of-the-art methodology enabling radical–radical coupling. The catalytic process involves forming an acyl azolium intermediate from the NHC catalyst and an acyl donor, followed by single electron reduction of this key intermediate, which is largely dependent on the photoredox catalyst. We designed a radical NHC catalysis in which the direct photoexcitation of a borate to form a high reducing agent facilitated the single electron reduction event. The borate produces an alkyl radical for the single electron transfer process to accomplish the radical–radical coupling. This protocol enables cross-coupling between alkylborates and acyl imidazoles in addition to radical relay-type alkylacylations of alkenes with alkylborates and acyl imidazoles, affording ketones with a broad scope.