Acetate and palladium

Interestingly, the Pd/PDMP catalyst is more active than commercially available homogeneous and heterogeneous palladium catalysts, such as palladium acetate and palladium on charcoal, respectively, as shown in Table 3. 

Furthermore, even the ligand, necessary to stabilize the catalyst, can reduce Pd(II) to Pd(0) complexes and formation of phosphine oxides [62-64], In the preparation of [Pd(AcO)2(dppp)], from Pd(AcO)2 and dppp in MeOH, phosphine oxides have been found to form together with methyl acetate and palladium metal [65]. The reaction can be schematized as follows ... 

A widely accepted mechanism for acetoxylation of ethylene is shown in equation (161) and consists of the nucleophilic attack of the acetate anion on the coordinated ethylene, followed by acetoxypalladation and /3-hydride elimination, giving vinyl acetate and palladium hydride.367... 

Alcohols in ethylene carbonate containing sodium acetate and palladium chloride are oxidized by oxygen at room temperature in 62-98% yields [70]. Oxygen passed at room temperature under irradiation through a solution of catalytic amounts of chloroplatinic acid and cuprous chloride in alcohols produces ketones in yields of up to 98% [57], Other catalysts used for this purpose are platinum [55], platinum-on-charcoal [56], and, better still, platinum oxide [56]. Such oxidations are carried out usually at room temperature and give fair to high yields. 

The arylation of enol esters has also been improved (95). Previously a wide range of products were produced including j8-aryl carbonyls, arylated enol esters, styrene, and stilbene derivatives (96). It has also been found that arylated enol esters can be obtained as major products if the reactions are carried out with stoichiometric amounts of aryl mercuric acetate and palladium acetate in anhydrous acetonitrile or in excess enol ester solution. The products are those arising from addition of the phenyl group to the carbons not containing the ester. Thus, with vinyl acetate and phenyl mercuric acetate, the product is the enol acetate of phenyl acetaldehyde ... 

Palladium(II) acetate and palladium(II) chloride (often applied as the soluble dibenzonitrile complex) are especially suited for cyclopropanation of strained double bonds as well as styrene and its ring-substituted derivatives. The good coordinating abilities of these pal-... 

Palladium(II) acetate and palladium(II) chloride (often applied as the soluble dibenzonitrile complex) are especially suited for cyclopropanation of strained double bonds as well as styrene and its ring-substituted derivatives.152,154,155 The good coordinating abilities of these palladium ) compounds, however, somewhat complicate the catalytic action and may even limit it. Thus, the presence of phosphane ligands in palladium(II) halides causes a significant induction period for decomposition of the diazocarbonyl compound,156 and the formation of stable palladium diene complexes may even prevent the cyclopropanation reaction.155,157 Furthermore, alkenes such as 4-dimethylaminostyrene and 4-vinylpyridine cannot be cyclo-propanated since their basic center deactivates the catalyst.155... 

In addition to l-chloro-2-methyl-4-acetoxybutene-2 (130), other C5 building blocks have also been tested with the C15 sulfone (13) to synthesize retinyl acetate (9). When this concept is realized industrially, cost-efficiency calculations may indicate that another C5 building block has to be used, so that the equation given may change slightly. It was also possible to alkylate the anion of the C 5 sulfone (13) with the dimeric allylpalladium tt complex (135) in the presence of a large excess of triphenylphosphine, the complex (135) being prepared from prenyl acetate and palladium(II) chloride (Manchand et al., 1978). 

Unsaturated Aldehydes and Ketones.—Successive treatment of silyloxycyclo-propanes with mercury(li) acetate and palladium(ii) chloride gives a-methylene ketones [equation (19)], and /3-trimethylsilylketones can be brominated and... 

Dissolve 7 g. of pure oleic acid in 30 ml. of dry ethyl chloride (chloroform may be used but is less satisfactory), and ozonise at about —30°. Remove the solvent under reduced pressure, dissolve the residue in 50 ml. of dry methyl alcohol and hydrogenate as for adipic dialdehyde in the presence of 0 5 g. of palladium - calcium carbonate. Warm the resulting solution for 30 minutes with a slight excess of semicarbazide acetate and pour into water. Collect the precipitated semicarbazones and dry the... 

There are also palladium-catalysed procedures for allylation. Ethyl 3-bromo-l-(4-methylphenylsulfonyl)indole-2-carboxylate is allylated at C3 upon reaction with allyl acetate and hexabutylditin[27], Ihe reaction presumably Involves a ir-allyl-Pd intermediate formed from the allyl acetate, oxidative addition, transmetallation and cross coupling. 

Both objectives have been met by designing special hydrogenation catalysts The most frequently used one is the Lindlar catalyst, a palladium on calcium carbonate combi nation to which lead acetate and quinoline have been added Lead acetate and quinoline partially deactivate ( poison ) the catalyst making it a poor catalyst for alkene hydro genation while retaining its ability to catalyze the addition of H2 to the triple bond... 

Lindlar catalyst (Section 9 9) A catalyst for the hydrogenation of alkynes to as alkenes It is composed of palladium which has been poisoned with lead(II) acetate and quino line supported on calcium carbonate... 

There are reports of an increasing number of palladium-assisted reactions, in some of which the palladium has a catalytic function. Thus furan and thiophene undergo facile palladium-assisted alkenylation giving 2-substituted products. Benzo[6 Jfuran and TV- acetyl-indole yield cyclization products, dibenzofurans and carbazoles respectively, in addition to alkenylated products (8UOC851). The arylation of pyrroles can be effected by treatment with palladium acetate and an arene (Scheme 86) (81CC254). 

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 ... 

The parent TMM precursor (1), now commercially available, has played a pivotal role in the execution of many synthetic plans directed at natural and unnatural targets. Reaction of (1) with 2-(methoxycarbonyl)cyclohexenone (14, R=C02Me) in the presence of palladium acetate and triethyl phosphite produced the adduct (15) in near quantitative yield. This cycloadduct is a critical intermediate in the total synthesis of a hydroxykempenone (16), a component of the defensive substances secreted by termites (Scheme 2.5) [12]. In accord with a previous observation by Trost that unactivated 2-cyclohexenone reacts poorly with TMM-Pd [13], the substrate (14, R=Me) was essentially inert in the cycloaddition. 

The above generalities apply particularly to palladium. Hydrogenation over platinum or rhodium are far less sensitive to the influence of steric crowding. Reduction of 1-t-butylnaphthalene over platinum, rhodium, and palladium resulted in values of /ci//c2 of 0.42, 0.71, and 0.024, respectively. Also, unlike mononuclear aromatics, palladium reduces substituted naphthalenes at substantially higher rates than does either platinum or rhodium. For example, the rate constants, k x 10 in mol sec" g catalyst", in acetic acid at 50 C and 1 atm, were (for 1,8-diisopropylnaphthalene) Pd (142), Pt(l8.4), and Rh(7.1)(25). 

Of this material 1.0 g is dissolved in 150 ml of warm 95% ethyl alcohol. To the solution is added 1.0 g of 5% palladium on carbon catalyst, and the mixture is hydrogenated at room temperature and atmospheric pressure by bubbling hydrogen into it for 3 hours with stirring. The hydrogenation product is filtered. The solid phase, comprising the catalyst and the desired product, is suspended in ethyl acetate and water and adjusted to pH 2 with hydrochloric acid. The suspension is filtered to remove the catalyst. The aqueous phase is separated from the filtrate, and is evaporated under vacuum to recover the desired product, 7-(D-a-aminophenylacetamido)cephalosporanic acid. 

Vinyl acetate was originally produced hy the reaction of acetylene and acetic acid in the presence of mercury(II) acetate. Currently, it is produced hy the catalytic oxidation of ethylene with oxygen, with acetic acid as a reactant and palladium as the catalyst ... 

Complete reduction to the alkane occurs when palladium on carbon (Pd/C) is used as catalyst, but hydrogenation can be stopped at the alkene if the less active Lindlar catalyst is used. The Lindlar catalyst is a finely divided palladium metal that has been precipitated onto a calcium carbonate support and then deactivated by treatment with lead acetate and quinoline, an aromatic amine. The hydrogenation occurs with syn stereochemistry (Section 7.5), giving a cis alkene product. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

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... 

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