Rhodium(III)-Catalyzed Oxidative Coupling of <i>N</i>-Phenylindole-3-carboxylic Acids with Alkenes and Alkynes via C4–H and C2–H/C2′–H Bond Cleavage
作者:Takeshi Okada、Asumi Sakai、Tomoaki Hinoue、Tetsuya Satoh、Yoshihiro Hayashi、Susumu Kawauchi、Kona Chandrababunaidu、Masahiro Miura
DOI:10.1021/acs.joc.8b00638
日期:2018.5.18
The rhodium(III)-catalyzed direct alkenylation of N-phenylindole-3-carboxylic acids with alkenes including acrylate ester, acrylamide, and acrylonitrile proceeds smoothly at the C4-position through regioselective C–H bond cleavage directed by the carboxyl group. In marked contrast, the indole substrates react with diarylacetylenes accompanied by cleavage of the C2–H and C2′–H bonds and decarboxylation
铑(III)催化的N-苯基吲哚-3-羧酸与包括丙烯酸酯,丙烯酰胺和丙烯腈在内的烯烃进行直接烯基化反应,通过羧基定向的区域选择性C–H键断裂,在C4位置顺利进行。与之形成鲜明对比的是,吲哚底物与二芳基乙炔反应,同时裂解C2-H和C2'-H键并脱羧生成5,6-二芳基吲哚[1,2- a]喹诺酮衍生物。DFT计算表明,将烯烃顺利插入到C4族基的六元金属环中间体中会导致C4烯基化的产物,而后者在C2-和C2'-位上的环化可归因于相应位置的轻松还原消除由双CH键断裂和炔烃插入形成的七元金属环。