Copper‐Catalyzed Radical‐Induced Annulation‐Halo(bi)cyanomethylation of Indole‐Tethered 1,6‐Enynes toward Pyrrolo[1,2‐<i>a</i>]indoles
Hang‐Dong Zuo, Ya‐Yu Yuan, Xi Chen, Jiyun Wang, Shenghu Yan, Yue Zhang, Jianwu Liu
Abstract
Abstract A copper‐catalyzed radical‐induced annulation‐halocyanomethylation of indole‐linked 1,6‐enynes has been established using haloacetonitrile as radical precursors, enabling the synthesis of 21 cyanomethylated pyrrolo[1,2‐ a ]indoles with yields ranging from 42% to 81% and a Z / E ratio up to 19:1. Moreover, by adjusting the reaction temperature, a variation of the annulation‐bromobicyanomethylation process was achieved, resulting in the production of 12 bicyanomethylated pyrrolo[1,2‐ a ]indole isomers in yields of 41–68%. The stereoisomeric mixture of bicyanomethylated products could be purified to their pure configurations through recrystallization. The proposed reaction mechanism was formulated through a series of control experiments.