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-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.

Bis(alkynyl) PTA and DAPTA complexes of Pt(II) and Pd(II)

“…Transition-metal complexes containing either PTA or DAPTA ligands have been reported for metals of groups 6-12 [3]. Metal-catalyzed reactions involving complexes with the PTA and DAPTA ligands are known for a variety of processes including hydrogenation [4], hydroformylation [4b], hydroamination [5], Aza-Morita-Baylis-Hillman [6], Suzuki [7], and Sonogashira couplings [8], and Baeyer-Villiger oxidation [9] reactions using water as a solvent or an aqueous biphasic solvent system [10]. A significant number of studies on the use of water soluble transition-metal complexes containing the PTA and DAPTA ligands for their medicinal and therapeutic applications are known with numerous studies involving ruthenium systems [3,11].…”

Nano‐ZnO Catalyzed Green and Efficient One‐Pot Four‐Component Synthesis of Pyranopyrazoles

“…With the growing concern over environment pollution and related societal health problems, green chemistry concept is emerging as one of the important tools in the development of environmentally benign chemical processes and clean technologies [4] including generation of solvent-free protocols along with replacement of easily volatile organic solvents by water as a green reaction medium [5]. Water is nonhazardous, inexpensive, abundant, and ecofriendly in nature having high boiling point.…”

Synthesis and characterization of palladium (II) complex of Schiff base ligand: CS bond cleavage and catalytic activity

“…namely phosphines, phosphates and phosphine oxides are used widely as catalyst in carbon-carbon and carbon-hetero atom bond formation [1][2][3][4]. These are expensive, toxic and unrecoverable and require air free handling due to their high sensitivity towards moisture and air [1][2][3][4]. In recent times nitrogen donor ligands such as N heterocyclic carbenes, imine and amine palladacycles, oxime palladacycles are used extensively as efficient partners for the C\C bond formation [5,6].…”

“…Palladium complexes in conjugation with the coligands viz. namely phosphines, phosphates and phosphine oxides are used widely as catalyst in carbon-carbon and carbon-hetero atom bond formation [1][2][3][4]. These are expensive, toxic and unrecoverable and require air free handling due to their high sensitivity towards moisture and air [1][2][3][4].…”