The suzuki reaction in aqueous media promoted by p, N Ligands

Abstract

The synthesis and structure of palladium complexes of trisubstituted PTA derivatives, PTAR3, 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- phosphabicyclo[3,3,1]nonane (RO-PTA), 3,7- diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane (DAPTA), lithium 1,3,5-triaza-7- phosphaadamantane-6-carboxylate (PTA-CO2Li), 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- phosphatricyclo[3.3.1.1]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 PPh2(m- C 6H 4SO 3Na) (TPPMS) and P(m-C 6H 4SO 3Na) 3 (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 2, (PTA R3)2PdCl 2 (R = Ph, p-tert-butylC 6H5), and PTA R3 (R = p-tert-butylC 6H 5) are reported.