Condensed thiophen ring systems. Part X. Synthesis and reactions of 2-aryl-1H-[1]benzothieno[2,3-b]pyrroles and 2-aryl-1H-[1]benzothieno[3,2-b]pyrroles

Abstract

Reductive cyclisation of a trans-1-aryl-2-(3-nitro-2-benzo[b]thienyl)- or a trans-1-aryl-2-(2-nitro-3-benzo[b]-thienyl)-ethene, respectively, with triethyl phosphite gave the title compounds. The trans-alkenes were prepared by the Wittig reaction from 3-nitrobenzo[b]thiophen-2-carbaldehyde or 2-nitrobenzo[b]thiophen-3-carbaldehyde, respectively. Improved methods for the preparation of these aldehydes are reported, together with some electrophilic substitution reactions of 2-phenyl-1H,-[1]benzothieno[3,2-b]pyrrole.