Palladium hydroxide

A surprising use of palladium hydroxide-on-carbon in the hydrogenation of (f )-a-phenylglycine to (R)-a-cyclohexylglycine was described by Tamura... 

Bj Preparation of 11 ji-Methoxy-A ° -Estratriene-3-ol-17-one 12.3 g of 11/3-methoxy-A -estradiene-3,17-dione were dissolved in 1,230 cc of methanol and then, under an atmosphere of nitrogen, 7.38 g of palladium hydroxide were added and the mixture was held at reflux for one hour under agitation and a nitrogen atmosphere. Then the reaction mixture was cooled to 30°C, filtered, vacuum filtered and washed with methanol. The metha-nolic solutions were concentrated to about 50 cc, allowed to stand overnight at room temperature and filtered. The precipitate formed was triturated in methanol and dried at 80°C to obtain 10.74 g (yield = 87.5%) of 11/3-methoxy-A " -estratriene-3-ol-17-one having a MP of 264°C. 

To a solution of l. 47 g (0.03 mol) of sodium cyanide and 4.73 g (0.03 mol) of (-)-(.S)-x-methylbenzylamine hydrochloride in 5 mL of cold water is added 1 g (8.3 mmol) of free ( - )-(.S )-a-mcthylbcnzylaininc in 200 mL of CHjOH. 1.32 g (0.03 mol) of acetaldehyde is added at 0°C and the clear solution is kept at r.t. for five days. After evaporation of the solvent in vacuo, the residue is dissolved in 50 mL of 1 N HC1 and the solution is extracted twice with diethyl ether. After addition of 12 N HCl to adjust the acid concentration to approximately 5 N, the solution is retluxed for 6 h. The HCl is evaporated in vacuo and the residue is dried over sodium hydroxide. The crude. V-x-methylbenzylalaninc hydrochloride is dissolved in 200 mL of 50% ethanol and the pH is adjusted to 6.0 with NaHCOj. To this solution, 3.5 g of palladium hydroxide is added. After hydrogenolysis for 10 h, the catalyst is filtered off and washed with hot water. The filtrate is concentrated to 30%, and the pH is adjusted to 1 with dilute IIC1. The solution is evaporated to dryness and the alanine hydrochloride is extracted with three 20-inL portions of absolute ethanol. After cooling overnight at — 50°C, the precipitated salt is filtered. Pyridine is added to the alcoholic solution to precipitate crude alanine, which is dissolved in 2.5 mL of water. The pH is adjusted with pyridine to 5.5-6.0, and 10 mL of absolute ethanol arc added yield 0.45 g (17% over four steps) mp 290 C [a] 7 + 13.13 (0 = 2.32. 6 N IICi). 

The diastereofacial selectivity is explained by the proposed chelated intermediate 151. Internal delivery of the nucleophile takes place from the less hindered side. Removal of the chiral directing moiety with a catalytic amount of palladium hydroxide on carbon in absolute ethanol then furnishes the final product. This process yields the amino ester in 83-100% yield without observable racemization. 

Palladium hydroxide on carbon (moist, Pd content 20%, dry weight basis, moisture content <50%) was purchased from Aldrich Chemical Company, Inc., and used as received. 

Finally, PdO particles are spontaneously formed from palladium hydroxide Pd(OH)2 via dehydration hy internal oxolation in agreement with the positive value of the partial charge of the water molecule (5h20 = 0.03). Figure 13.3 summarizes the overall mechanism leading to the formation of PdO colloidal particles. 

The oxidation of olefins to carbonyl compounds by palladium (II) ion can be regarded as an addition of a palladium hydroxide group to the olefin followed by a hydrogen shift. Kinetic evidence suggests the following mechanism for the oxidation of ethylene by palladium chloride in aqueous solution containing excess chloride ion 21, 49, 99). 

For palladium hydroxide on calcium carbonate mix hot solutions of 55 g of anhydrous calcium chloride and 53 g of anhydrous sodium carbonate each dissolved in 150 ml of distilled water. Filter the resulting precipitate of calcium... 

For preparative purposes the cleavage of the ozonide is best carried out by catalytic hydrogenation over palladium hydroxide-on-calcium carbonate, a catalyst system which does not hydrogenate the aldehydic products the yield of the latter are usually fairly good. An alternative procedure for the decomposition of the ozonide is treatment with dimethylsulphide in methanol the use of the less obnoxious thiourea is a good alternative.107... 

Hydrogenolysis of the benzyl group of 9-benzyloxy-4//-pyrido[ 1,2-a]pyrimidin-4-ones 336 in ethanol over 10% palladium-on-charcoal under pressure of hydrogen (3 atm), or in the presence of cyclohexene and 10% palladium hydroxide, afforded 9-hydroxy derivatives 337 in 25-30% and 78% yield, respectively (89TL1529 91JHC1287). 

The hydrobromide of l-(p-hydroxyphenyl)-2-(p-phenylbutylamino)propanone-1 was suspended in very pure methanol and shaken with a 10% palladium hydroxide barium sulfate catalyst in contact with, hydrogen. After rather more than 2 mols of hydrogen had been taken-up the hydrogenation stopped. The l-(p-hydroxyphenyl)-2-(3-phenylbutylamino)propanol-l, was filtered, washed with methanol and evaporated, melting point 110-111°C. 

Valine methyl ester, (S)-, hydrochloride Benzyl chloroformate Palladium hydroxide... 

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