Regioselective Couplings of Dibromopyrrole Esters

The regioselectivity of the Suzuki couplings of several 4,5- and 3,4-dibromopyrrole-2-carboxylate esters has been studied. In general, regioselectivity can be achieved for initial coupling at the more electron-deficient site (C5 and C3, respectively). At the same time, conversions are often modest (40-60%) and attempts to force the reactions to higher conversions often lead to competitive dicoupling.