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[b]thiophenes and their hetero-fused analogues, such as thieno[2,3-b]thiophenes, indolo[2,3-b]thiophenes, and pyrazolo[3,2-c]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, S-methyl xanthates, methyl N-imidazolyl dithioate, N-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[b]- and/hetero-fused thiophenes in high yields.