Direct arylation of dithienylperfluorocyclopentenes via palladium-catalysed C-H bond activation: a simpler access to photoswitches

The palladium-catalysed direct arylation of dithienylperfluorocyclopentene (DTE) derivatives proceeds in moderate to high yields with a variety of aryl bromides in the presence of 5 mol% Pd(OAc)(2)/dppb as the catalyst, and KOAc as the base. The use of cyclopentyl methyl ether as the solvent was found to be crucial to avoid the decomposition of the reactants and products. The reaction proceeds regioselectively at C5 of thiophenes, and tolerates various substituents such as formyl, acetyl, ester, nitrile or nitro on the aryl bromide. Therefore, this method allows a straightforward modulation of the electron density distribution on DTE derivatives.