Bithiophene-fusedbenzo[c]phospholes were successfully prepared by a TiII-mediated cyclization of dialkynylated bithiophene derivatives. It was revealed that the optical and electrochemical properties of the bithiophene-fusedbenzo[c]phospholes are deeply related to the π-conjugation modes at the fused bithiophene subunits. Both experimental and theoretical results demonstrate that the appropriately
prepared by Ti(II)-mediated cyclization of the corresponding dialkynylated bithiophene derivatives as a key step. Each sigma(3)-phosphorus center of the benzo[c]phosphole subunits was readily transformed into sigma(4)-phosphorus center by Au coordination or oxygenation. In addition, the bithiophene subunit was functionalized at the alpha,alpha'-carbon atoms by Pd-catalyzed cross-coupling reactions with heteroarylmetals