The Suzuki reaction in aqueous media promoted by P, N ligands

The synthesis and structure of palladium complexes of trisubstituted PTA derivatives, PTA(R3), are described. Water-soluble phosphine ligands 1,3,5-triaza-7-phosphaadmantane (PTA), tris(aminomethyl)phosphine trihydrobromide, tri(aminomethyl) phosphine, 3,7-dimethyl-1,5,7-triaza-3-phosphabicyclo3,3,1]nonane (RO-PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo3.3.1]nonane (DAPTA), lithium 1,3,5-triaza-7-phosphaadamantane-6-carboxylate (PTA-CO?Li), 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo 3.3.1.1]decane, and 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo3.3.1.1]decane were used as ligands for palladium catalyzed Suzuki reactions in aqueous media. RO-PTA in combination with palladium acetate or palladium chloride was the most active catalyst for Suzuki cross coupling of aryl bromides and phenylboronic acid at 80 °C in 1:1 water:acetonitrile. The activity of Pd(II) complexes of RO-PTA is comparable to PPh?(m-C?H?SO?Na) (TPPMS) and P(m-C?H?SO?Na)? (TPPTS) and less active than tri(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt (TXPTS). Activated, deactivated, and sterically hindered aryl bromides were examined, with yields ranging from 50% to 90% in 6 h with 5% palladium precatalyst loading. X-ray crystal structures of (RO-PTA)PdCl?, (PTA(R3))?PdCl? (R = Ph, p-tert-butylC?H?), and PTA(R3) (R = p-tert-butylC?H?) are reported.