Platinum oxide, catalyst hydrogenation

In presence of platinum oxide as catalyst in methyl alcohol, it hydrogenates to dihydrowogermine, which darkens >265° and melts at 277-8° (dec.) [a]n ° — 61° (pyridine). The dihydro-base still contains eight... 

A solution of 50 g of 1 -azabicyclo [2.2.2] -3-octanone hydrochloride in 200 cc of water was hydrogenated at room temperature and 50 atm pressure with 1 g of platinum oxide as catalyst. After the calculated amount of hydrogen had been absorbed, the mixture was filtered and concentrated in vacuo to dryness. The residual product was recrystallized from a mixture of methanol and acetone and formed prisms melting above 300°C. It was identified as 1 -ezabicy-clo[2.2.2] -3-octanol hydrochloride. 

The product (12.1 mg) obtained in the above step was dissoived in 0.3 mi of water, to which was then added a catalytic quantity (about 5 mg) of platinum oxide. Hydrogenation was made with hydrogen gas at a pressure of 35 kg/cm for 1.5 hours. The reaction solution was filtered to remove the catalyst, and the filtrate was concentrated to dryness, giving the desired product 3, 4 -dideoxykanamycin B in the form of its monocarbonate. The yield was 11.5 mg (95%). -f 110° (c 1, water). The overall yield of 3, 4 -dideoxykanamycin B... 

Catalytic hydrogenation of methanolic solutions of the 4-nitroimidazoles (72 R1 = D-glucopyranosyl, D-arabinopyranosyl, D-xylopyranosyl R2 = H) using platinum oxide as catalyst gave the corresponding 4-aminoimidazole nucleosides (71 R1 = D-glucopyranosyl, D-arabinopyra-nosyl, D-xylopyranosyl R2 = H) (yields 16, 33, and 25%, respectively), which were apparently isolated as the free bases but no mention of the stability of these compounds was made (72LA67). 

In fine chemical manufacturing, the application of promoted platinum catalysts is less known. Maxted and Akhar have reported that the addition of stannous, manganous, ceric and ferric chloride to platinum oxide (Adams catalyst) facilitates the hydrogenation of aldehydes, ketones and olefins (ref. 1). The selective hydrogenation of unsaturated aldehydes or ketones to unsaturated alcohols has been achieved by the addition of ferrous sulfate and zinc acetate to platinum catalysts (ref. 2). 

Experimental Details—A solution of 12.8 g. of 4,6-benzylidene-D-gIucose, m. p. 185-186°, in 150 cc. of 95% ethanol was shaken with hydrogen in the presence of 1.5 g. of platinum oxide (Adams catalyst) at room temperature and an initial pressure of 50 pounds per square inch. The reduction was complete in eighteen hours with the absorption of approximately one mole-equivalent of hydrogen. Concentration of the filtered solution yielded 10.5 g. (82%) of 4,6-benzylidenesorbitol, m. p. 131-134°. Recrystallization from ethanol by the addition of ether yielded the pure compound, m. p. 132-133°. 

Amidone (6-dimethylamino-4,4-diphenyl-3-heptanone), while resistant to hydrogenation with Raney nickel, could be hydrogenated to the alcohol with platinum oxide as catalyst.140 However, isoamidone (6-dimethylamino-4,4-diphenyl-5-methyl-3-hexanone)(15, R = Me) did not absorb hydrogen in the presence of platinum oxide and the reduction to the corresponding alcohol was achieved by reduction with lithium aluminum hydride.141... 

Smith and Utley hydrogenated indoles and 1,2,3,4-tetrahydrocarbazoles in about 1 1 ethanol-aqueous fluoroboric acid at room temperature and atmospheric pressure using platinum oxide as catalyst. The yields of the corresponding indolines and hexahy-drocarbazoles were very high or quantitative as analyzed by GC (Table 12.3).16 It has been suggested that the species that was subjected to hydrogenation might be the indoles protonated at the 3 position (8) with the C=N double bond in the indolenine system. 

Catalytic hydrogenation of fluoro- and difluOTO-m- and tran -butenedioic acids and their esters frequently affords products only of hydrogenolysis, especially when platinum oxide (Adams catalyst) is used. Hydrogenolysis is favored in polar solvents, and is found to be more effective when rhodium or nickel rather than palladium are used as the catalysts (Table 2). Hydrogenolysis takes place prior to the saturation of the double bonds fluoro- and 2,3-difluoro-succinic acids do not suffer any loss of fluorine under the same reaction conditions. ... 

Hydrogenation using a palladized calcium carbonate catalyst in neutral solution gives 94 per cent, amorphous base, which is obtained in 100 per cent, yield using platinum oxide as catalyst. It is bis-6 6 -dihydrodesoxycodeine-D [x], identical with the product obtained from a-chlorocodide [23],... 

Vanillin (3.04 g, 0.02 mol), dissolved in a minimum amount of absolute ethanol, was combined with 2.66 g of aminoacetaldehyde diethylacetal (0.02 mol), and the mixture was diluted to 15 mL with absolute ethanol and hydrogenated at atmospheric pressure and room temperature over 200 mg of previously reduced platinum oxide. Hydrogen consumption stopped at about 90% completion after about 3 h. The catalyst was removed by filtration and the solvent was evaporated under vacuum. The residual oil was dissolved in 50 mL concentrated hydrochloric acid. The solution which had become hot was cooled and washed with three 30-mL portions of 3 2 ether-benzene to remove starting aldehyde. A two-fold excess of benzaldehyde (4.24 g, 0.04 mole) dissolved in 50 mL of ethanol was added to the acidic solution which was subsequently boiled for 30 min. The cooled solution was diluted with an equal volume of water and washed with three 50-mL portions of ether to remove the excess benzaldehyde. The solution was made basic with ammonium hydroxide to pH 8. The precipitate was removed by filtration and crystallized once from water-ethanol to give 3.33 g of 4-benzyl-6-hydroxy-7-methoxyisoquinoline, in a yield of 63%, m.p. 185-190°C. The analytical sample has m.p. at 192-193°C. 

Using platinum oxide as catalyst, aliphatic ketones in HF are reduced by hydrogen to hydrocarbons. Rearrangements typical of carbonium ion intermediates are observed. "... 

Structural changes in PEM and catalyst layers due to platinum oxidation or catalyst contamination under open-circuit conditions On/off cyclic operation under different humid conditions Effect of hygro-thermal cycle on membrane stresses Water uptake effect on cyclic stress and dimensional change, hydrogen crossover... 

Scheme 12.31. A scheme for the synthesis of N-glutamate (Glu, E) by the formation of an imine from a-ketoglutarate and N-labeled ammonium chloride ( NH4C1) followed by reduction with hydrogen (H2) in the presence of a platinum oxide (PtO,) catalyst. See, for example, Kragl, U. Godde, A. Wandry, C. Kinzy, W. Cappon, J. X Lugtenburg, X Tetrahedron Assymetry, 1993, 6,1193.

A mixture of 10.0 g (0.03 mol) of 3,3-diphenyl-6-nitrophthalide, 0.2 g of platinum oxide (Adams Catalyst-Alfa Inorganics, Inc.) and 0.03 mol of hydrochloric acid in 250 mL of 95% ethanol was hydrog-nated in a Parr Pressure Reaction Apparatus model 3911. The initial pressure was set at 55 psi and the mixture was shaken until the hydrogen uptake was completed. The mixture was filtered, and the ethanol was removed under vacuum. The crude amine was recrystallized from 95% ethanol. The yield was 8.6 g (92%) m.p. 153.5-155.0 C. 

Adams catalyst, platinum oxide, Pt02 H20. Produced by fusion of H2PtCl6 with sodium nitrate at 500-550 C and leaching of the cooled melt with water. Stable in air, activated by hydrogen. Used as a hydrogenation catalyst for converting alkenes to alkanes at low pressure and temperature. Often used on Si02... 

Use 01 g. of the platinum oxide catalyst and 11 4 g, of pure cinnamic acid dissolved in 100 ml. of absolute alcohol. The theoretical volume of hydrogen is absorbed after 7-8 hours. Filter off the platinum, and evaporate the filtrate on a water bath. The resulting oil solidifies on cooling to a colourless acid, m.p. 47-48° (11-2 g.). Upon recrystallisation from light petroleum, b.p. 60-80°, pure dihydrocinnamic acid, m.p. 48-49°, is obtained. 

Place a solution of 10 -4 g. of benzalacetophenone, m.p. 57° (Section IV,130) in 75 ml. of pure ethyl acetate (Section 11,47,15) in the reaction bottle of the catalytic hydrogenation apparatus and add 0 2 g. of Adams platinum oxide catalyst (for full experimental details, see Section 111,150). Displace the air with hydrogen, and shake the mixture with hydrogen until 0 05 mol is absorbed (10-25 minutes). Filter oflF the platinum, and remove the ethyl acetate by distillation. RecrystaUise the residual benzylacetophenone from about 12 ml. of alcohol. The yield of pure product, m.p. 73°, is 9 g. 

Hydrocinnamic acid may also be prepared by the reduction of cinnamic acid with sodium and alcohol or with sodium amalgam or with hydrogen in the presence of Adams platinum oxide catalyst (Section 111,150) ... 

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