Hydrogen peroxide-Palladium acetate

METHYL KETONES AUyltrimethyl-silane, Bis(acetonitrilo)chloronitro-palladium (11). Dicarb ony lbis( triphenyl-phosphine)nickel. Dichloro-dicyano-benzoquinone. Hydrogen peroxide-Palladium acetate. Meldrum s acid. Palladium r-butyl peroxide trilluoro-acctate. Palladium tl) chloride. 

Hydrogen peroxide, 201-203 Hydrogen peroxide-Palladium acetate,... 

Reduction of 2-carbamoylpyrazine in ethanol over palladium-charcoal at atmospheric pressure gave 2-carbamoylpiperazine (870, 1269, 1352), and the 2-carbamoyl-3-carboxy (1269) and 2,3-dicarbamoyl (1269, 1352) analogues were prepared similarly, but 2,3-dicarboxypyrazine imide gave 50% 2,3-dicarboxy-1,4,5,6-tetrahydropyrazine imide (1269). 2-Hydroxy-3-V-phenylcarbamoylpyrazine oxidized with hydrogen peroxide in acetic acid at 50° for 96 hours did not give an 7V-oxide but only a tar and 2,3-dihydroxypyrazine (1055). 

Other Methods.— The palladium-catalysed oxidation of terminal olefins to methyl ketones is very efficient using 30% hydrogen peroxide in acetic acid or t-butyl alcohol. The method offers advantages in that conversions are usually high, aldehyde production is very low, and the method requires only very low concentrations of palladium [20—40p.p.m, as palladium(li) acetate], fi-Hydroxy-o-nitrophenylselenides, or their O-acyl derivatives, on oxidation with hydrogen peroxide undergo elimination to form ketones or enol esters [equation (10)]. The starting materials can be prepared easily from alkenes via their epoxides. 

The method is basically an application of the Wacker oxidation except that the catalyst used is palladium acetate ( Pd(AcO)2 or Pd(02CCH3)2). the solvent is acetic acid or tert-butyl alcohol and the oxygen source is the previously suggested hydrogen peroxide (H202)[17]. 

Palladium(II) effects orthometalation of acetanilides to form the corresponding palladacycles [185]. De Vries, van Leeuwen, and coworkers exploited this reactivity to achieve regioselective oxidative coupling of acetaniUdes and n-butyl acrylate that proceeds efficiently with BQ as the stoichiometric oxidant (Eq. 46) [ 186], The use of TsOH as an additive and acetic acid as a cosolvent significantly improves the results. Inferior results are observed with hydrogen peroxide or copper(II) acetate as the stoichiometric oxidant, but efforts to use molecular oxygen were not described. 

Finally, a,[3-unsaturated carbonyl compounds are converted to [3-keto systems when treated with 20% Na2PdCl4 catalyst in 50% acetic acid as solvent and r-butyl hydroperoxide or hydrogen peroxide as reoxidant (equation 3).9 It is not clear if the mechanism of this process is related to the other palladium(II)-catalyzed addition of oxygen nucleophiles to alkenes. 

The oxidation of a,p-unsatuiated caibraiyl compounds under the usual conditions in DMF using PdCl2/CuCl/02 is very slow. However, regioselective oxidation of oc, -unsaturated esters to p-keto esters (equation IS), and a,p-unsaturated ketones to 1,3-diketones (equation 16) proceeds with NazPdCU in solvents such as 50% acetic acid, isopropyl alcohol, and NMP. r-Butyl hydroperoxide and hydrogen peroxide are used as the reoxidants of the reduced palladium. The reaction proceeds slowly at room temperature but smoothly between 50 and 80 C. Some typical examples of this process are shown in Table 1. 

Nickel peroxide. Oxoperoxobis(N-phenylbenzohydroxamato) molyb-denum(VI). Palladium(II) acetate-Tri-phenylphosphine. Palladium /-butyl peroxide trifluoroacetate. Periodic acid. Permonophosphoric acid. Potassium dichromate. Potassium hydrogen persulfate. Pyridinium dichromate. Ruthenium tetroxide. Selenium dioxide. Sodium hypochlorite. Titanium(IlI) chlo-ride-Hydrogen peroxide. Potassium nitrodisulfonate. Potassium peroxodi-sulfate. Pyridinium chlorochromate. Pyridinium chlorochromate-Hydrogen peroxide. Sodium permanganate monohydrate. Tetra-n-Butylammonium periodate. Thailium(III) acetate. Trimethyl-amine N-oxide. Triphenylmethylphos-phonium permanganate. 

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