Palladium II Acetate

Solubility sol organic solvents such as chloroform, methylene chloride, acetone, acetonitrile, diethyl ether. Dissolves with decomposition in aq HCl and aq KI solutions. Insol water and aqueous solutions of NaCl, NaOAc, NaNOs as well as in alcohols and petroleum ether. Decomposes when heated with alcohols. 

Form Supplied in orange-brown crystals generally available. Preparative Method preparation of palladium diacetate from palladium sponge was developed by Wilkinson et al. Purification palladium nitrate impurities can be removed by recrystallization from glacial acetic acid in the presence of palladium sponge. 

General Considerations. Salts of palladium that are soluble in organic media, for example Pd(OAc)2, dUitbium tetra-chloropalladate(II), and PdCl2(RCN)2, are among the most extensively used transition metal complexes in metal-mediated organic synthesis. Palladium acetate participates in several reac- 

Alkenes cort5)lexed to Pd are readily attacked by nucleophiles such as water, alcohols, carboxylates, amines, and stabilized carbon nucleophiles (eq 1). Attack occurs predominantly from the face opposite to that of the metal trans attack), thus forming a new carbon-nucleophile bond and a carbon-metal cr-bond. 

The transformations in eqs 1 and 2 ultimately produce palla-dium(0), whilepaUadium(II) is required to activate alkenes (eq 1). Thus, if such a process is to be run using catalytic amounts of the noble metal, a way to rapidly regenerate palladium(II) in the presence of both substrate and product is required. Often this reoxidation step is problematic in palladium(II)-catalyzed nucleophilic addition processes, and reaction conditions have to be tailored to fit a particular type of transformation. A number of very useful catalytic processes, supplementing the processes that employ stoichiometric amounts of the metal, have been developed.  

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Diphenylimidazole with palladium acetate forms the cyclometallated complex 80 (X = OAc) (97AOC491). The acetate group is replaced by chloride or bromide when 80 (X = OAc) reacts with sodium chloride or lithium bromide, respectively, to give 80 (X = C1, Br). Bromide with diethyl sulfide forms the mononuclear complex 81. Similar reactions are known for 1 -acetyl-2-phenylimidazole (96JOM(522)97). 1,5-Bis(A -methylimidazol-2-yl)pen-tane with palladium(II) acetate gives the cyclometallated complex 82 (OOJOM (607)194). 

Dimethylbenzimidazolium iodide serves as a starting material for free carbenes (99CEJ1931, 99JA10626, 00AGE541) and carbene complexes (99JOM(585)241). Thus, with palladium(II) acetate it gives [L Pdl ] where L is... 

Dimethyl-1,2,4-triazolium iodide with palladium acetate yields the carbene adduct 182 (97JOM(530)259). Under water it undergoes cis-trans isomerization to 183. Some other derivatives were reported in 1981 (81BCSJ800). 1,1 -Methylenebis(4-alkyl-l,2,4-triazolium)diiodides (alkyl = /-Pr, n-Bu, octyl) with palladium(II) acetate give the mononuclear complexes [L Pdl ] (99EJIC1965), where L2= l,l -methylenebis(4-R-l,2,4-triazol-2-ylidene) (R = /-Pr, n-Bu, octyl). Thermolysis of the products in THF gives the rran -dinuclear complexes 184... 

R = /-Pr, n-Bu, octyl). The reaction of l,r-methylenebis(4-methyl-l,2, 4-tria2olium)diiodide with palladium(II) acetate however proceeds differently and gives the cationic dicarbene [L2Pd(02CMe)]I. 

Methylphenyl)benzothiazole (80IC762) and 2-benzylbenzothiazole (95ICA(239)125) can be cyclopalladated. In the latter case, cylopalladation occurs upon reaction with palladium(II) acetate and gives the product 80. With lithium chloride, sodium bromide, or sodium iodide, a series of three products of substitution of the acetate group 81 (X = C1, Br, I) results. Pyridine, 2- and 3-methylpyridine, 2,6- and 3,5-dimethylpyridine cause the transformation of the chelate complexes 81 (X = C1, Br, I) and formation of the mononuclear products 82 (R = z= R" = = R = H, X = Cl, Br, I ... 

Treatment of ethyl 1 W-azepine-l-carboxylate with palladium(II) acetate in benzene, or in an aprotic solvent, results in ring contraction (see Section 3.1.2.4.) or ring opening (vide infra), respectively, however, with palladium(II) acetate in acetic acid ethyl 2,3-diacetoxy-2,3-dihydro-l//-azepine-l-carboxylate (6) is formed as the major product along with ( , )-hexa-2,4-dienedial.243... 

In the presence of aqueous acetic acid the 4//-azepi ne 9 yields the hydroxy derivative 10 a. Addition of methanol, in the presence of Sephadex LH20, and cyanide ion in the presence of palladium(II) acetate, are also successful and yield 4,5-dihydro-l //-azepines 10b and 10c, respectively.113... 

The reaction of l//-l,2-diazepines with palladium(II) acetate in the presence of sodium acetate gives dienes in low yield, e.g. the reaction of ethyl l/f-l,2-diazepine-l-carboxylate (1).91,92... 

The exocyclic C — C double bond in the chlorin can be reduced by catalytic hydrogenation in tetrahydrofuran/water in the presence of palladium(II) acetate with triethoxysilane as hydrogen source to yield under kinetic control cw-stereoisomers, which can be transformed by treatment with /)-toluenesulfonic acid in methanol to the thermodynamically favored trans-isomers.27d... 

Palladiumphthalocyanine (PcPd) can be synthesized from phthalimide, ammonium molyb-date(VI), urea and palladium(II) chloride in nitrobenzene.285 Peripherally substituted palladium phthalocyanine is prepared by the reaction of phthalonitrile286 or isoindolinediimine114,117 and palladium(II) acetate in 2-(dimethylamino)ethanol. Also a metal insertion into metal-free phthalocyanine in dimethylfonnamide starting from bis(triphenylphos-phane)palladium(II) chloride has been performed.141,287... 

There is significant metal-metal bonding in the platinum compound, whose geometry involves a square of platinum atoms another important difference is that the coordination geometry is square planar in palladium acetate but octahedral in the platinum analogue. Different oligomers exist in solution, broken down by adduct formation. Palladium(II) acetate may be obtained as brown crystals from the following reaction [65] ... 

In a remarkable reaction according to Eq. 18 palladium(II) acetate reacts in methanol with diphenylacetylene to form dinuclear [Pd(T 5-C5Ph5)]2(p-PhC = CPh) (67) [79], The reaction mechanism was studied in some detail and part of the alkyne molecule was found as benzoic acid orthoester PhC(OMe)3. When... 

Dioxane, palladium (II) acetate, and triphenylphosphine were purchased from Aldrich Chemical Company, Inc. and were used without further purification. 

Palladium(II) acetate reacts with N,N, N"-triphenylguanidine ( = HTpg) in warm benzene to form a bis-adduct which, under more forcing conditions, converts to the novel dinuclear guanidinate-bridged complex [Pd(/L-Tpg)... 

Various l-alkyl-4-(benzotriazol-l-yl)-l,2,3,4-tetrahydroquinolines have been prepared by condensation of V-alkylaniline with two equivalents of an aldehyde and one equivalent of benzotriazole <95JOC(60)7631>. Quinolones 66 were simply prepared in good yield by heating a mixture of the appropriate vinylogous amide 65 and NaHCOj in the presence of a catalytic amount of palladium(II) acetate and triphenylphosphine in DMF under a carbon monoxide atmosphere <96CC2253>. 

Palladium(II) acetate was found to be a good catalyst for such cyclopropanations with ethyl diazoacetate (Scheme 19) by analogy with the same transformation using diazomethane (see Sect. 2.1). The best yields were obtained with monosubstituted alkenes such as acrylic esters and methyl vinyl ketone (64-85 %), whereas they dropped to 10-30% for a,p-unsaturated carbonyl compounds bearing alkyl groups in a- or p-position such as ethyl crotonate, isophorone and methyl methacrylate 141). In none of these reactions was formation of carbene dimers observed. 7>ms-benzalaceto-phenone was cyclopropanated stereospecifically in about 50% yield PdCl2 and palladium(II) acetylacetonate were less efficient catalysts 34 >. Diazoketones may be used instead of diazoesters, as the cyclopropanation of acrylonitrile by diazoacenaph-thenone/Pd(OAc)2 (75 % yield) shows142). 

Intramolecular oxonium ylide formation is assumed to initialize the copper-catalyzed transformation of a, (3-epoxy diazomethyl ketones 341 to olefins 342 in the presence of an alcohol 333 . The reaction may be described as an intramolecular oxygen transfer from the epoxide ring to the carbenoid carbon atom, yielding a p,y-unsaturated a-ketoaldehyde which is then acetalized. A detailed reaction mechanism has been proposed. In some cases, the oxonium-ylide pathway gives rise to additional products when the reaction is catalyzed by copper powder. If, on the other hand, diazoketones of type 341 are heated in the presence of olefins (e.g. styrene, cyclohexene, cyclopen-tene, but not isopropenyl acetate or 2,3-dimethyl-2-butene) and palladium(II) acetate, intermolecular cyclopropanation rather than oxonium ylide derived chemistry takes place 334 ). 

A palladium-catalyzed protocol for carbon-sulfur bond formation between an aryl triflate and para-methoxybenzylthiol was introduced by Macmillan and Anderson (Scheme 6.66) [138], Using palladium(II) acetate as a palladium source and 2,2 -bis(diphenylphosphino)-l,l -binaphthyl (BINAP) as a ligand, microwave heating of the two starting materials in N,N-dimethylformamide at 150 °C for 20 min in the presence of triethylamine base led to the formation of the desired sulfide in 85% yield. 

In a related study, Srivastava and Collibee employed polymer-supported triphenyl-phosphine in palladium-catalyzed cyanations [142]. Commercially available resin-bound triphenylphosphine was admixed with palladium(II) acetate in N,N-dimethyl-formamide in order to generate the heterogeneous catalytic system. The mixture was stirred for 2 h under nitrogen atmosphere in a sealed microwave reaction vessel, to achieve complete formation of the active palladium-phosphine complex. The septum was then removed and equimolar amounts of zinc(II) cyanide and the requisite aryl halide were added. After purging with nitrogen and resealing, the vessel was transferred to the microwave reactor and irradiated at 140 °C for 30-50 min... 

The catalyst reported by Drent [48] was generated in situ by mixing a palladium source with the ligand. A palladium source is broadly defined as a complex or any form of palladium metal whereby upon mixing with the ligand an active catalyst is formed. Many palladium sources are possible, but the sources exemplified by Drent aretris(dibenzylideneacetone)dipalladium(0)(Pd2(dba)3),bis(dibenzylideneacetone) palladium(O) (Pd(dba)2), or palladium(II) acetate. 

The diester 226 undergoes ring-closure to the methylenecyclopentane derivative 227 in the presence of a catalytic amount of chlorotris(triphenylphosphine)rhodium in boiling chloroform saturated with hydrogen chloride. In contrast, if the reaction is catalysed by palladium(II) acetate, the isomeric cyclopentene 228 is produced (equation 115)118. 

Leadbeater NE, Pillsbury SJ, Shanahan E, Williams VA (2005) An assessment of the technique of simultaneous cooling in conjunction with microwave heating for organic synthesis. Tetrahedron 61 3565-3585 Lee CKY, Holmes AB, Ley SV, McConvey IF, Al-Duri B, Leeke GA, Santos RCD, Seville JPK (2005) Efficient batch and continuous flow Suzuki crosscoupling reactions under mild conditions, catalysed by polyurea-encapsulated palladium (II) acetate and tetra-n-butylammonium salts. J Chem Soc Chem Commun 2175-2177... 

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