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 [126.96.36.199]decane, and 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[188.8.131.52]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, (PTAR3)2PdCl2 (R = Ph, p-tert-butylC6H5), and PTAR3 (R = p-tert-butylC6H5) are reported.
Keywords: C–C coupling; aqueous phase Suzuki reaction; 1,3,5-triaza-7-phosphaadamantante (PTA); water-soluble phosphine ligands
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Weeden, J.A.; Huang, R.; Galloway, K.D.; Gingrich, P.W.; Frost, B.J. The Suzuki Reaction in Aqueous Media Promoted by P, N Ligands. Molecules 2011, 16, 6215-6231.
Weeden JA, Huang R, Galloway KD, Gingrich PW, Frost BJ. The Suzuki Reaction in Aqueous Media Promoted by P, N Ligands. Molecules. 2011; 16(8):6215-6231.
Weeden, Jason A.; Huang, Rongcai; Galloway, Kathryn D.; Gingrich, Phillip W.; Frost, Brian J. 2011. "The Suzuki Reaction in Aqueous Media Promoted by P, N Ligands." Molecules 16, no. 8: 6215-6231.