Synthesis of Trisubstituted Alkenes via Direct Oxidative Arene–Alkene Coupling

The
use of an inorganic oxidant with an acetic acid/acetonitrile
solvent combination has been identified as optimal for direct arene/1,2-disubstituted
alkene oxidative couplings, providing an efficient route to trisubstituted
alkenes. The acetonitrile cosolvent dramatically accelerates the rate
of reaction, and an insoluble inorganic oxidant limits unwanted oxidation
of substrates. The scope of this procedure is illustrated with arenes
and alkenes containing electron-donating and -withdrawing substituents
resulting in a general synthetic strategy to trisubstituted alkenes.
In situ ESI-MS analysis of the reaction components has identified
the key Pd intermediates in the Fujiwara–Moritani catalytic
cycle.

研究表明，采用无机氧化剂结合乙酸/乙腈(acetonitrile)混合溶剂体系，是实现直接芳烃/1,2-二取代烯烃氧化偶联反应的最优方案，可高效制备三取代烯烃。乙腈助溶剂可显著提升反应速率，而不溶性无机氧化剂能够抑制底物发生非目标氧化副反应。该合成方法的适用范围通过带有给电子与吸电子取代基的芳烃和烯烃得到验证，由此建立了一条通用的三取代烯烃合成策略。通过对反应组分开展原位电喷雾质谱(ESI-MS)分析，已成功鉴定出藤原-森谷(Fujiwara–Moritani)催化循环中的关键钯(Pd)中间体。