钯催化全取代吡唑导向的C(sp^2)—H键后期芳基化反应

Fully Substituted Pyrazoles Assisted Palladium-Catalyzed Late-Stage Arylation of C(sp^2)-H Bond

发展了一种钯催化全取代吡唑类化合物的邻位C(sp2)—H键后期芳基化的反应体系.通过对反应条件的优化,得到了最高效的芳基化反应条件.该催化体系表现出广泛的底物适用性、良好的官能团耐受性以及优良的分离收率.进行了控制实验,如分子间的竞争实验和放大克级实验,氘代动力学实验证明了C—H键的断裂是决速步骤.最后,通过制备双核二聚体环钯化中间体,提出了合理的钯催化循环反应机理.

A successful protocol has been developed for palladium-catalyzed late-stage arylation of fully substituted pyrazoles.Through screening of optimazation of reaction parameters,the most efficient reaction conditions for mono-orthoposition arylation were obtained.This reaction features a broad substrate scope,good functional group tolerance as well as good to excellent yield.Moreover,the intermolecular competition experiments and gram scale reaction were also performed.The kinetic isotopic effect(KIE)result reveled C—H bond cleavage was involved in the rate-limiting step and a plausible mechanism was proposed based on the dual-core dimeric palladacycle.