Visible-Light-Driven External-Reductant-Free Cross-Electrophile Couplings of Tetraalkyl Ammonium Salts
Visible-Light-Driven External-Reductant-Free Cross-Electrophile Couplings of Tetraalkyl Ammonium Salts
复制标题
可见光驱动的四烷基铵盐的无外部还原剂交叉电偶合
DOI：
10.1021/jacs.8b08792
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发表时间：
2018-12-19
影响因子：
15
通讯作者：
Yu, Da-Gang
中科院分区：
文献类型：
--
作者：
Liao, Li-Li;Cao, Guang-Mei;Yu, Da-Gang
在化学计量的外部还原剂存在下，两个亲电试剂之间的交叉亲电试剂偶联是生成C-C键的有力且经济的方法。在此，我们报道了一种通过可见光光氧化还原催化实现第一个无外部还原剂的交叉亲电偶联的新策略。各种带有伯、仲和叔C-N键的四烷基铵盐与醛/酮和CO2进行选择性偶联。值得注意的是，原位产生的副产物，三甲胺，被有效地用作电子供体。此外，该方案具有反应条件温和、催化剂负载量低、底物范围广、官能团耐受性好、易于扩展等优点。机理研究表明，苄基自由基和阴离子可能是通过亲电偶联反应生成的关键中间体，为交叉亲电偶联反应提供了新的方向。
Cross-electrophile couplings between two electrophiles are powerful and economic methods to generate C-C bonds in the presence of stoichiometric external reductants. Herein, we report a novel strategy to realize the first external-reductant-free cross-electrophile coupling via visible-light photoredox catalysis. A variety of tetraalkyl ammonium salts, bearing primary, secondary, and tertiary C-N bonds, undergo selective couplings with aldehydes/ketone and CO2. Notably, the in situ generated byproduct, trimethylamine, is efficiently utilized as the electron donor. Moreover, this protocol exhibits mild reaction conditions, low catalyst loading, broad substrate scope, good functional group tolerance, and facile scalability. Mechanistic studies indicate that benzyl radicals and anions might be generated as the key intermediates via photocatalysis, providing a new direction for cross-electrophile couplings.