Palladium acetate copper salts

The situation has now changed and currently an area of considerable research interest is in heterogenizing homogeneous catalysts. One such instance is to be found in the ethylene based manufacture of vinyl acetate (11). A homogeneous catalytic process based on palladium and copper salts was first devised, but corrosion problems were made much less serious in a heterogeneous system based on the same chemical principles. 

In some preliminary studies on the eflFect of the metallic anion a series of reactions was run in which chloride in both the palladium and copper salts was replaced by other anions. When acetate was used, results similar to the chloride systems were obtained although product distribution was somewhat different see also Table 1). Both bromide and iodide were found to inhibit the reaction, and no products were isolated. For the oxyanions, nitrate, sulfate, and acetylacetonate, vinyla-tion products of these oxyanions in addition to the acetate vinylation products were found. Because of the increased complexity of these systems, they were not investigated further. All chloride-containing systems investigated—PdCl2, Na2PdCl4, (NH3)2PdCl2, and 7r-allylpalladium chloride—had similar reactivities and vinylation-product distributions. 

Diazonium salts react with oximes to give aryl oximes, which are easily hydrolyzed to aldehydes (R = H) or ketones." A copper sulfate-sodium sulfite catalyst is essential. In most cases higher yields (40-60%) are obtained when the reaction is used for aldehydes than for ketones. In another method for achieving the conversion ArNj —> ArCOR, diazonium salts are treated with R4Sn and CO with palladium acetate as catalyst. In a different kind of reaction, silyl enol ethers of aryl ketones, Ar C(OSiMe3)=CHR, react with sohd diazonium fluoroborates, ArNj BF4, to give ketones, ArCHRCOAr. " This is, in effect, an arylation of the aryl ketone. 

Carboxylic acids can be prepared in moderate-to-high yields by treatment of diazonium fluoroborates with carbon monoxide and palladium acetate or copper(II) chloride. The mixed anhydride ArCOOCOMe is an intermediate that can be isolated. Other mixed anhydrides can be prepared by the use of other salts instead of sodium acetate." An arylpalladium compound is probably an intermediate." ... 

The Suzuki coupling of aryl halides was also extended to tosylates recently. Benzothiazole 5-tosylate reacted with m-xylene-2-boronic acid (6.13.) to give the coupled product in 94% yield using palladium acetate and a stericly congested biphenyl based phosphine ligand as catalyst.17 Another class of less commonly utilised cross-coupling partners are methyltio derivatives. In the presence of a copper salt, which activates the carbon-sulphur bond, 2-methyltio-benzotiazol coupled readily with a series of arylboronic acids.18... 

Methylene ( CH2) generated photochemically or thermally from diazomethane is highly reactive and is prone to incur side reactions to a substantial extent. In order to avoid these undesirable complexities, the cyclopropanation of multiple bonds with diazomethane has usually been carried out under catalytic conditions The catalysts most frequently employed are copper salts and copper complexes as well as palladium acetate. The intermediate produced in the copper salt-catalyzed reactions behaves as a weak electrophile and exhibits a preference to attack an electron-rich double bond. It is also reactive enough to attack aromatic nuclei. In contrast, the palladium acetate-catalyzed decomposition of diazomethane cyclopropanates a,a- or a,jS-disubstituted a,jS-unsaturated carbonyl compounds in high yields (equation 47). The trisubstituted derivatives, however, do not react. The palladium acetate-catalyzed reaction has been applied also for the cyclopropanations of some strained cyclic alkenesstyrene derivatives and terminal double bondsHowever, the cyclopropanation of non-activated, internal double bonds occurs only with difficulty. The difference, thereby. 

In the following mechanistic proposals, monomeric species have been written for economy of space. In the absence of cupric salts, with large excesses of acetate present, it is unknown whether the species are monomeric or dimeric in palladium although the monomeric species seem most probable. However, in the presence of cupric salts, the most likely species are those like XI, dimeric in palladium and copper. In these... 

Shi has reported a method for /V-alkylanilidc arylation by simple arenes [53], The reaction conditions include heating the anilide with excess arene in propionic acid in the presence of catalytic palladium acetate and copper triflate under oxygen atmosphere. Use of monosubstituted arenes leads to the formation of isomer mixtures however, from the point of atom economy C-H/C-H couplings are the most efficient way for formation of C-C bonds if oxygen is used as the terminal oxidant. Shi has also reported that anilides can be coupled with arylboronic acids and trialkoxyaryl-silanes [54, 55], Silver and copper salts are used as terminal oxidants. 

A selectivity of 96% was obtained when the reaction was carried out in the gas phase at 130oC with a palladium chloride-copper acetate-magnesium chloride catalyst.30 The reaction has also been run in a eutectic mixture of copper chloride-potassium chloride at 150°C, with 94-96% selectivity to dimethyl carbonate and 2-5% selec-tivty to methyl ether (2.8).31 After the product distils out, the molten salt can be used for the next run. 

Allylic acetoxylation with palladium(II) salts is well known however, no selective and catalytic conditions have been described for the transformation of an unsubstituted olefin. In the present system use 1s made of the ability of palladium acetate to give allylic functionalization (most probably via a palladium-ir-allyl complex) and to be easily regenerated by a co-oxidant (the combination of benzoquinone-manganese dioxide). In contrast to copper(II) chloride (CuClj) as a reoxidant,8 our catalyst combination is completely regioselective for allcyclic alkenes with aliphatic substrates, evidently, both allylic positions become substituted. As yet, no allylic oxidation reagent is able to distinguish between the two allylic positions in linear olefins this disadvantage is overcome when the allylic acetates are to... 

The effect of silver salts, copper acetate and mercury acetate as an additive was studied in the palladium-catalyzed carbonylation of nitrobenzene [17]. The combination of palladium acetate, sliver fluoride, 1,10-phenanthroline and p-toluen-sulfonic acid were found to be highly active and selective yielding nitrobenzene conversion up to 96 %. Copper acetate and mercury acetate are also effective as additives and gave good results. A-phenylcarbamate was produced in the presence of alcohol. 

Anion Source for Palladium Catalysis. The reagent serves as a source of weakly coordinating anions in the palladium-catalyzed formation of mixed phenyl ureas, a known class of commercially available herbicides, using palladium(II) acetate, copper(II) toluenesulfonate, and 2,2 -dipyridyl as the catalyst system. Other studies have suggested that use of this reagent to form palladium salts may have useful applications in the reductive carbonylation of nitroaromatic compounds to give isocyanates via initial carbamate formation (eq 2). ... 

Earlier studies have also shown that a catalyst system consisting of palladium(II) and copper salts plus oxygen for the reoxidation did not work well,t in contrast to the result with the Wacker oxidation. However, if quinone or hydroquinone was added to a mixture of palladium acetate and copper acetate, oxygen could be used as an efficient oxidant for conversion of alkenes into allylic acetates. Thus, cyclohexene gave better than 85% cyclohexenyl acetate (Scheme 10). The combination of oxygen and cobalt or manganese acetate also works, but less well.t ... 

Showa Denko has developed such a direct oxidation process and commercialized the technology in 1997 (100000ta ). The catalyst consists of three components (i) palladium supported on a carrier (0.1-2 wt%) (ii) a heteropoly add (e.g., phos-photungstic acid or silicotungstic acid) or its related lithium, sodium and copper salts (iii) selenium, tellurium, copper, silver, tin, lead, antimony, or bismuth. The process is operated in a fixed bed reactor at 150-160 °C and up to 8 bar. The gas stream entering the reactor consists of the reactants ethylene and oxygen, steam, and nitrogen as diluent. Water/steam is needed because it enhances the activity and selectivity of the reaction. The selectivity to acetic acid is 86%. The main byproducts are carbon dioxide and not fully converted acetaldehyde. 

---