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

• Published in: Molecules (Basel, Switzerland) Switzerland), 2011-07, Vol.16 (8), p.6215-6231
• Main Authors: Weeden, Jason A, Huang, Rongcai, Galloway, Kathryn D, Gingrich, Phillip W, Frost, Brian J
• Format: Article
• Language: English
• Subjects: 1,3,5-triaza-7-phosphaadamantante (PTA); Adamantane - analogs & derivatives; aqueous phase Suzuki reaction; Boronic Acids - chemistry; Bromides - chemistry; Carbon; Catalysis; Chemistry, Organic - methods; Crystallography, X-Ray; C–C coupling; Insecticides - chemical synthesis; Ligands; Nanoparticles; Nitrogen - chemistry; Organophosphorus Compounds; Palladium; Palladium - chemistry; Phosphines - chemical synthesis; Phosphorus - chemistry; Solubility; Water; water-soluble phosphine ligands
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules16086215

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-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-C₆H₄SO₃Na) (TPPMS) and P(m-C₆H₄SO₃Na)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)PdCl₂, (PTA(R3))₂PdCl₂ (R = Ph, p-tert-butylC₆H₅), and PTA(R3) (R = p-tert-butylC₆H₅) are reported.