Palladium hydroxide/carbon

Palladium hydroxide-carbon Prim, amines from sec. benzylamines... 

Preparation of palladium - calcium carbonate catalyst. Prepare 60 g. of precipitated calcium carbonate by mixing hot solutions of the appropriate quantities of A.R. calcium chloride and A.R. sodium carbonate. Suspend the calcium carbonate in water and add a solution containing 1 g. of palladium chloride. Warm the suspension until all the palladium is precipitated as the hydroxide upon the calcium carbonate, i.e., until the supernatant liquid is colourless. Wash several times with... 

C. Palladium on carbon catalyst (5 per cent. Pd). Suspend 41-5 g. of nitric acid - washed activated carbon in 600 ml. of water in a 2-litre beaker and heat to 80°. Add a solution of 4 1 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (prepared as in A), followed by 4 ml. of 37 per cent, formaldehyde solution. Stir the suspension mechanically, render it alkaUne to litmus with 30 per cent, sodium hydroxide solution and continue the stirring for a further 5 minutes. Filter off the catalyst on a Buchner funnel, wash it ten times with 125 ml. portions of water, and dry and store as in B. The yield is 46 g. 

Diacetone-L-sorbose (DAS) is oxidized at elevated temperatures in dilute sodium hydroxide in the presence of a catalyst (nickel chloride for bleach or palladium on carbon for air) or by electrolytic methods. After completion of the reaction, the mixture is worked up by acidification to 2,3 4,6-bis-0-isoptopyhdene-2-oxo-L-gulonic acid (2,3 4,6-diacetone-2-keto-L-gulonic acid) (DAG), which is isolated through filtration, washing, and drying. With sodium hypochlorite/nickel chloride, the reported DAG yields ate >90% (65). The oxidation with air has been reported, and a practical process was developed with palladium—carbon or platinum—carbon as catalyst (66,67). The electrolytic oxidation with nickel salts as the catalyst has also... 

The catalyst is previously prepared in an apparatus for catalytic hydrogenation, in which are placed 0.5 g. of palladous chloride, 3.0 g. of Norite, and 20 ml. of distilled water. The bottle is swept out with hydrogen and then shaken with hydrogen for 2-3 hours at 2-3 atmospheres (40 lb.) pressure. The palladium on carbon is collected on a Biichner funnel, washed with five 50-ml. portions of distilled water, then with five 50-ml. portions of 95% ethanol, and finally twice with ether. Upon drying, about 3 g. of the catalyst is obtained. It is stored in a vacuum desiccator over solid sodium hydroxide. If the reduction of the chloro-lepidine does not proceed normally, the used catalyst should be removed by suction filtration and a fresh 3-g. portion of catalyst added. Failure of the reduction step is usually due to an inactive catalyst or to impurities in the acetic acid or chlorolepidine. The palladium catalysts, prepared as described elsewhere in this volume, are presumably also satisfactory for the reduction of 2-chlorolepidine (p. 77). 

The palladium on carbon catalysts should be dried at room temperature or the carbon may ignite. These catalysts are first dried in air and then over potassium hydroxide (or calcium chloride) in a desiccator. 

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

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. 

The most common method for achieving aromatization of compounds such as 72 is with phosphorus oxytrichloride and the addition of dimethylformamide (DMF Scheme 1) (see, for example, <1996CHEC-II(7)921>, and more recently, <2004M283, 1997S567>). Reductive dechlorination of 73 with palladium on carbon in the presence of sodium hydroxide affords the corresponding heterocycle 74 (Scheme 1) <2004M283>. 

Controlled reduction of 2,2 -dinitrobiphenyl is achieved with 2, 1, and 0.5 molar equivalents of sodium borohydride in the presence of palladium on carbon and sodium hydroxide to give benzo[c]cinnoline, its /V-oxide, and AT V -dioxide, respectively, in high yields (Scheme 6). 

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... 

Ammonia Hydrochloric acid Palladium on carbon Sodium hydroxide... 

Codeine sulfate trihydrate Ammonium hydroxide Aluminum isopropoxide Potassium sodium tartrate tetrahydrate Palladium on carbon... 

Sodium hydride Hydrochloric acid Aluminum chloride o-Phosphoric acid Sodium hydroxide Palladium on carbon Sodium borohydride l,3-Dihydro-l-benzyl-2H-benzimidazol-2-one... 

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