Copper‐Catalyzed Radical‐Induced Annulation‐Halo(bi)cyanomethylation of Indole‐Tethered 1,6‐Enynes toward Pyrrolo[1,2‐a]indoles

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 exceeding 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 the 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 controlled experiments.