Catalyst, Adams

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... 

For more selective hydrogenations, supported 5—10 wt % palladium on activated carbon is preferred for reductions in which ring hydrogenation is not wanted. Mild conditions, a neutral solvent, and a stoichiometric amount of hydrogen are used to avoid ring hydrogenation. There are also appHcations for 35—40 wt % cobalt on kieselguhr, copper chromite (nonpromoted or promoted with barium), 5—10 wt % platinum on activated carbon, platinum (IV) oxide (Adams catalyst), and rhenium heptasulfide. Alcohol yields can sometimes be increased by the use of nonpolar (nonacidic) solvents and small amounts of bases, such as tertiary amines, which act as catalyst inhibitors. 

Ammonium chloroplatinate often can be used to advantage in place of chloroplatim c acid in the preparation of Adams catalyst. A mixture of 3 g. of ammonium chloroplatinate and 30 g. of sodium nitrate in a casserole or Pyrex beaker is heated gently at first until the rapid evolution of gas slackens and then more strongly until a temperature of 500° is reached. This operation requires about fifteen minutes and there is no spattering. The temperature is held at 500-520° for one-half hour and the mixture is then allowed to cool. The platinum oxide catalyst, collected in the usual way by extracting the soluble salts with water, weighs 1.5 g. and it is comparable in appearance and in activity to the material prepared from chloroplatinic acid. 

Cyanohydrin (52b 5 g mp 160-164°) is dissolved in acetic acid (200 ml) and placed in a 2-liter hydrogenation flask. Adams catalyst (0.75 g) is added (for 100 g cyanohydrin use 7.5 gof catalyst) and the mixture is hydrogenated until the theoretical amount of hydrogen is taken up (477 ml). The catalyst is removed by filtration, the filtrate is transferred to a 600 ml beaker provided with a stirrer and thermometer, treated with water (20 ml) and cooled to 0° (ice-salt). A solution of sodium nitrite (10 g) in water (30 ml) is added dropwise with stirring at 0°. The reaction mixture is then stirred for additional 2 hr at room temperature, treated with water (100 ml) and, after standing overnight, the precipitate is collected by filtration. The product is dissolved in ether (50 ml), the ether solution is washed sequentially... 

Hydrogenation with Adams catalyst took place only with the 6-alkyl derivatives. Dioxohexahydrotriazine itself acted as a catalyst poison (in common with 1,3,5-triazine and cyanuric acid ). Dioxo-tetrahydrotriazine as well as its A-alkyl and 6-alkyl derivatives can be readily hydrogenated by using Raney nickel. ... 

Oxidation of the hexahydro to tetrahydro derivatives was mentioned in connection with the synthesis of 3,5-dioxo-l,2,4-triazines (e.g., Section II,B,2,a). The reverse procedure, hydrogenation of the tetrahydro derivatives, was used with 6-azauracil, 6-azathymine, and their iV-methyl derivatives. With all these compounds hydrogenation proceeds smoothly in the presence of Adams catalyst. Only the hydrogenation of l-methyl-6-azathymine was not successful. ... 

Anhydro-bases derived from quaternary )S-carbolinium salts are reduced to p /r-A-substituted-l,2,3,4-tetrahydro-j8-carboline derivatives on hydrogenation over Adams catalyst in methanol solution made alkaline to ensure the presence of anhydro-base. ... 

Support for this suggestion comes from many quarters. Reduction of the jS-carboline anhydro-bases with sodium and alcohol or with tin and hydrochloric acid gives the 1,2,3,4-tetrahydro derivatives, as does catalytic reduction over platinum oxide in an alkaline medium. On the other hand, catalytic reduction with platinum oxide in acetic acid results in the formation of the 5,6,7,8-tetrahydro-j3-carbolinium derivatives (see Section III,A,2,a). It should be noted, however, that reduction of pyrido[l,2-6]indazole, in which the dipolar structure 211 is the main contributor to the resonance hybrid, could not be effected with hydrogen in the presence of Adams catalyst. 

Condensation of 2-quinolinecarboxaldehyde 98 with acetylacetone or ethyl acetate gave the acrylate derivatives 99 and 100, respectively. Cyclization of 99 with AC2O afforded the benzindolizine 101 (80ACSA(B)79). Reduction of 100 in presence of Adams catalyst followed by hydrolysis gave 102 (78PJC107) (Scheme 19). 

To 20 g of the above compound dissolved in 300 ml 95% ethanol In a Parr reaction vessel is added 1.5 g Adams catalyst, platinum dioxide, and the mixture shaken under hydrogen at 50 psi for 1 hour at ambient temperature. The mixture Is then filtered and the ethanol removed on a standard rotary evaporator. The resulting oil is dissolved in 200 ml ether and slowly added to 1,200 ml ether with continuous stirring. The product separates as crystals which are removed after 15 to 30 minutes by filtration. The compound melts at 148°C to 147°C and needs no further purification. 

Platinum and palladium are the most common catalysts for alkene hydrogenations. Palladium is normally used as a very fine powder supported" on an inert material such as charcoal (Pd/C) to maximize surface area. Platinum is normally used as PtC, a reagent called Adams catalyst after its discoverer, Roger Adams. 

Adams catalyst (Section 7.7) The Pt02 catalyst used for hydrogenations. 

Friedel-Crafts reaction Adams, Roger. 230 Adams catalyst, 230 Addition reaction, 137... 

Other methods of reducing the nitroso compound include the use of ammonium sulfide4 and hydrogenation utilizing Adams catalyst.5... 

Direct hydrogenation of key intermediate 248 over the Adams catalyst and subsequent lithium aluminum hydride reduction yielded the two stereoisomeric alcohols 256 and 257, which were separately transformed to ( )-corynantheal (258) and ( )-3-epicorynantheal (259), respectively, by Moffatt oxidation, followed by Wittig reaction with methyltriphenylphosphonium bromide and, finally, by demasking the aldehyde function (151, 152). 

Reflux 6.9 g triphenylphosphine and 6.6 g lauryl bromide (or equimolar amount of homolog) in 40 ml xylene for 60 hours. Remove solvent and wash residue with 5X20 ml ether (by decanting) to get 11 g lauryl triphenylphosphonium bromide (I). To a stirred suspension of 5.6 g (0.011M)(I) in 50 ml ether add 0.01M butyllithium solution (see Organic Reactions 8,258(1954) for preparation). Stir Vz hour at room temperature and slowly add 1.66 g 3,5-dimethoxybenzaldehyde (preparation given elsewhere here) in 10 ml ether over Vi hour. After 15 hours, filter, wash filtrate with water and dry, evaporate in vacuum. Dilute residue with pentane, filter and remove solvent. Dissolve the residual oil in 25 ml ethyl acetate and hydrogenate over O.lg Adams catalyst at one atmosphere and room temperature for 2 hours. Filter and evaporate in vacuum to get the 5-alkylresorcinol dimethyl ether which can be reciystallized from pentane and demethylated as described elsewhere here. 

The selectivity in favor of the desired monobenzylated product was found to be >99% and the immobilized Pt02 was found to be 4-5 times more active than the commercial Adams catalysts. In solution or in immobilized form, the PtOz colloid is effective in the hydrogenation of carbonyl compounds or of olefins. Recently, the heterogeneous catalytic amination of aryl bromides by immobilized Pd(0) particles has been reported [163], Secondary amines such as piperidine and diethyl amine are used in the amination of aryl bromides and the reaction proceeds with good turnover numbers and regio-control. The catalysts can be reused repeatedly without loss of activity or selectivity after filtration from the reaction mixture. 

Reetz, M.T. and Koch, M., Water-soluble colloidal Adams catalyst preparation and use in catalysis,... 

Carbon reacts also with other sulfur-containing compounds with resulting fixation of sulfur. Reaction of various forms of carbon with hydrogen sulfide was reported by Baraniecky, Riley, and Streeter (126) and by Polansky, Knapp, and Kinney (128). The reaction of carbon blacks with hydrogen sulfide and with sulfur was studied extensively by Studebaker (86). At 150°, the increase in sulfur content was proportional to the quinone content as measured by catalytic hydrogenation using Adams catalyst (see page 203). 

Ferber and Bruckner reduced />-aminobenzoic acid using Adams catalyst (Pt02) at atmospheric pressure, and Schneider and Dillman reduced p-aminobenzoic acid using 10% rhodium on carbon at 140 atm. and 70°. 3-Isoquinuclidone has been prepared, by the previously mentioned investigators, by heating the dry 4-aminocyclohexane carboxylic acid at elevated temperatures. 

Platinum (IV) oxide (Pt" + 20 —> Pt O ) is also known as platinum dioxide. It is a dark-brown to black powder known as Adams catalyst that is used as a hydrogenation catalyst. 

Hydroxy-N-Methylisomorphinan. 24 mg of the 3-hydroxy-delta-6-dehydro-N-methyl-morphan is hydrogenated over 5 mg of Adams catalyst in 15 cc of dcohol. H2 uptake is complete after 35 min. The solution is filtered, concentrated, and the residue is ciystallized from benzene to yield 24 mg of colorless fine prisms. 

Conversion of the keto ketoxime 1 to the exo-exo-amino alcohol 2 has been accomplished by hydrogenation over Adams catalyst and by reduction with lithium aluminum hydride. Amino alcohol 2 has also been prepared from 1 by a two-stage process in which selective reduction of the ketone is carried out with sodium borohydride, and the resultant hydroxy oxime is reduced with lithium aluminum hydride or by hydrogenation over Adams catalyst. ... 

Nitraramine and A-hydroxynitraramine were isolated from Nitraria schoberi (194,195). There are active hydrogen absorption bands in the IR spectrum of nitraramine at 3280 and 3530 cm- and a low intensity band at 1660 cm" (double bond). Acetylation of nitraramine (171) gave A-acetyl and A,0-diacetyl derivatives. Hydrogenation over Adams catalyst in acetic acid gave di-hydronitraramine (172) and dihydrodesoxynitraramine (173) (Scheme 30). The presence of peaks typical for quinolizidine alkaloids in the mass spectra of 171-... 

Scheme 14, Reaction conditions i, CH3COCI ii, H2, Adams catalyst.

Formula Pt02 MW 227.08 forms mono-, di-, and tetrahydrates Synonyms platinum(lV) oxide platinic oxide Adams catalyst... 

Platinum dioxide, also known as Adams catalyst, is used commercially in many hydrogenation reactions at ordinary temperatures, such as reduction of olefinic and acetylenic unsaturation, aromatics, nitro, and carbonyl groups. 

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