Palladium-catalyzed coupling reaction of 3-bromo benzo[b]furan, -thiophene and -selenophene 2-carboxaldehyde. Preparation of tetracyclic heteroaromatic derivatives

Article abstract of DOI:10.1515/znb-2006-0409

3-Oxo-2,3-dihydrobenzo[b]furans, -thiophenes and -selenophenes 1a-c afforded the bromo-aldehydes 2 under Vilsmeier-Haack-Arnold conditions. Palladium-catalysed aryl-aryl coupling of 2 with o-formyl-phenylboronic acid allowed the formation of dialdehydes 3 which underwent McMurry cyclisation or pinacol condensation to yield polycyclic aromatic derivatives 4 or the dihydroxylated compounds 5.