Qin Jing-Hao, Luo Mu-Jia, An De-Lie, Li Jin-Heng
State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, 410082, China.
Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang, 330063, China.
Angew Chem Int Ed Engl. 2021 Jan 25;60(4):1861-1868. doi: 10.1002/anie.202011657. Epub 2020 Nov 24.
A cobalt-promoted electrochemical 1,2-diarylation of alkenes with electron-rich aromatic hydrocarbons via direct dual C-H functionalizations is described, which employs a radical relay strategy to produce polyaryl-functionalized alkanes. Simply by using graphite rod cathode instead of platinum plate cathode, chemoselectivity of this radical relay strategy is shifted to the dehydrogenative [2+2+2] cycloaddition via 1,2-diarylation, annulation, and dehydrogenation cascades leading to complex 11,12-dihydroindolo[2,3-a]carbazoles. Mechanistical studies indicate that a key step for the radical relay processes is transformations of the aromatic hydrocarbons to the aryl sp -hybridized carbon-centered radicals via deprotonation of the corresponding aryl radical cation intermediates with bases.
描述了一种钴促进的烯烃与富电子芳烃通过直接双C-H官能化进行的电化学1,2-二芳基化反应，该反应采用自由基接力策略来制备多芳基官能化烷烃。只需使用石墨棒阴极而非铂板阴极，这种自由基接力策略的化学选择性就会通过1,2-二芳基化、环化和脱氢级联反应转变为脱氢[2+2+2]环加成反应，生成复杂的11,12-二氢吲哚并[2,3-a]咔唑。机理研究表明，自由基接力过程的关键步骤是通过用碱使相应的芳基自由基阳离子中间体去质子化，将芳烃转化为芳基sp-杂化的碳中心自由基。
