Palladium-catalysed direct regiospecific arylation at C5 of thiophenes bearing SO2R substituents at C3

A palladium catalyzed direct arylation of thiophenes substituted at C3 by SO2R substituents was found to be fully selective in favor of carbon C5. This reaction allows the synthesis of a wide variety of 5-aryl-3-sulfonic acid derivs. using as little as 0.5-1 mol% of palladium acetate [Pd(OAc)2] as a catalyst in only one step. The synthesis of the target compd. was achieved by a reaction of 3-[(diethylamino)sulfonyl]-2-thiophenecarboxylic acid ester (I) with aryl bromides. such as 1-(4-bromophenyl)ethanone. The title compds. thus formed included a 5-[4-(acetyl)phenyl]-N,N-diethyl-mv 3-thiophenesulfonamide deriv. (II) and related substances. Similarly, 5-aryl-3-thiophenesulfonic acid Ph esters, such as a thiophenesulfonic acid Ph ester (III) and related substances were also formed. [on SciFinder(R)]