One-Pot Synthesis of Functionalized Benzo[<i>b</i>]thiophenes and Their Hetero-Fused Analogues via Intramolecular Copper-Catalyzed S‑Arylation of In Situ Generated Enethiolates

Abstract

An efficient one-pot synthesis of highly functionalized multisubstituted benzo­[<i>b</i>]­thiophenes and their hetero-fused analogues, such as thieno­[2,3-<i>b</i>]­thiophenes, indolo­[2,3-<i>b</i>]­thiophenes, and pyrazolo­[3,2-<i>c</i>]­thiophenes, has been reported. The overall strategy involves sequential base-mediated condensation of 2-bromohet­(aryl)­acetonitrile precursors with (het)­aryl/alkyl dithioesters or other thiocarbonyl species such as dimethyl trithiocarbonate, <i>S</i>-methyl xanthates, methyl <i>N</i>-imidazolyl dithioate, <i>N</i>-alkyl dithiocarbamate, and phenyl isothiocyanate, followed by intramolecular copper-catalyzed arylthiolation of in situ generated enethiolates, furnishing a broad range of 2-functionalized 3-cyanobenzo­[<i>b</i>]- and/hetero-fused thiophenes in high yields