Synthesis of 2,5-di(2-thienyl)-1H-pyrrole N-linked with conjugated bridges

The Knorr–Paal reaction of 1,4-di(2-thienyl)-1,4-butanedione with anilines to yield N-substituted-2,5-di-(2-thienyl)-1H-pyrroles (SNS derivatives) was tested by using different acid catalysts in toluene and acetic acid. Di-SNS derivatives were also synthesized in toluene at reflux in the presence of propionic acid, these mild conditions giving acceptable yields in a one-step procedure.