C–H Alkenylation of Heteroarenes: Mechanism, Rate, and Selectivity Changes Enabled by Thioether Ligands
作者:Bradley J. Gorsline、Long Wang、Peng Ren、Brad P. Carrow
DOI:10.1021/jacs.7b03887
日期:2017.7.19
catalytic intermediate in these reactions may also account for unusual catalyst-controlled site selectivity wherein C–H alkenylation of five-atom heteroarenes can occur under electronic control with thioether ligands even when this necessarily involves reaction at a more hindered C–H bond. The thioether effect also enables short reaction times under mild conditions for many O-, S-, and N-heteroarenes (55 examples)
已确定硫醚辅助配体可以大大促进O-,S-和N的C–H烯基化-杂芳烃。动力学数据表明,硫醚-Pd催化的反应比经典的无配体系统快800倍之多。此外,机理研究表明,C–H键的裂解是限制周转的步骤,硫醚配位时的速率加速与该关键步骤从中性途径向阳离子途径的变化相关。在这些反应中形成阳离子型,低配位的催化中间体也可能说明了催化剂控制位点的异常,其中五原子杂芳烃的CH链烯基化可以在硫代配体的电子控制下发生,即使这必然涉及在更阻碍了CH键的键合。硫醚效应还使得许多O-,S-和N-杂芳烃(55个实例),包括晚期药物衍生化的实例。