Different Performance of Two Isomeric Phosphinobiphenyl Amidosulfonates in Pd-Catalyzed Cyanation of Aryl Bromides

A hydrophilic phosphinobiphenyl amidosulfonate, 2′-(dicyclohexylphosphino)-2{[(sulfonatomethyl)amino]carbonyl}[1,1′-biphenyl], triethylammonium salt (L2), was prepared and, together with its isomer bearing the polar amido-sulfonate tag in the position 4 of the biphenyl scaffold (compound L1), evaluated as a supporting ligand in Pd-catalyzed cyanation of aryl bromides using K4[Fe(CN)6] as the non-toxic cyanide source. The less sterically demanding ligand L1 was found to form more active catalysts than the newly prepared compound L2. A catalyst formed in situ from palladium(II) acetate and L1 efficiently mediated cyanation of aryl bromides bearing electron-donating substituents but failed in the analogous reactions with electron-poor substrates.