Synthesis and some transformations of 2-(2-thienyl)-1(3)H-imidazo[4,5-f] quinoline

2-(2-Thienyl)-1(3)H-imidazo{cm4,5-f]}quinoline was synthesized by the Weidenhagen reaction of quinoline-5,6-diamine with thiophene-2-carbaldehyde. Its methylation in the system KOH-DMSO gave isomeric 1-methyl-2-(2-thienyl)-1H- and 3-methyl-2-(2-thienyl)-3H-imidazo{cm4,5-f]}quinolines, the latter being the major product. The 3-methyl derivative was subjected to electrophilic substitution reactions (bromination, nitration, formylation, acylation, sulfonation). Depending on the conditions, electrophilic attack was directed at the thiophene or quinoline fragment or both these.