Photochemical cyclisation of some iodophenyl- and iodothienyl-(thienyl)-ethylenes

The photoconversion of some iodophenyl(thienyl)ethylenes and iodothienyl(thienyl)ethylenes to naphthothiophens and benzodithiophens respectively has been carried out. The results suggest that the intermediate in these cyclisations is likely to be a dihydro-derivative, which suffers dehydrogenation, rather than an aryl radical which effects an intramolecular substitution.