Synthesis of 6-(2’ or 4’- nitrophenyl)benzo[b]thiophenes by Palladium-catalyzed cross-coupling

The palladium-catalyzed cross-coupling reactions of organoboron compounds are very useful for carbon-carbon bond formation. Compounds 1 were synthesized by a palladium-catalyzed cross-coupling of bromo or iodonitrobenzenes with boronic esters 2, which were prepared from methylated 6- bromobenzo[b]thiophenes2 by halogen-metal exchange and transmetalation. The intermediates esters 2 were not isolated but directly, after evaporation of the ether, coupled in acetone/water using palladium acetate in the presence of sodium hydrogencarbonate. Yields of isolated compounds 1 were about 40%.