Dithieno-annulated benzo[g]coumarins: Synthesis via oxidative photocyclization and study of their photophysical properties

Dithieno-annulated benzo[g]coumarins were synthesized in excellent yields using a facile photochemical oxidative cyclization method. These π-expanded benzocoumarins displayed strong absorption in the near-UV/visible region. Moreover, they revealed visible blue to yellow emission in solution when compared to simple benzo[g]coumarins or thienoannulated coumarins. This suggests their possible use in bio-imaging.