Adams catalyst Alcohols

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. 

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. 

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). 

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. ... 

It is well established that oxygen in the presence of platinum (Adams catalyst) can achieve specific oxidation of secondary alcohols by a preferential attack upon hydrogen in an equatorial position (25). Catalytic oxidation of methyl a- and /3-D-galactopyranoside (26), fallowed by catalytic reduction with hydrogen, led to the formation of methyl a- and /3-6-deoxy-D-galactopyranoside (D-fuco-pyranoside) in 15% and 35% yield, respectively. This oxidation-reduction sequence with selective oxidation at carbon 4 as the initial step is structurally closely related to the above described pathway for TDPG-oxidoreductase. 

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). 

Phenylethylamine has been made by a number of reactions, many of which are unsuitable for preparative purposes. Only the most important methods, from a preparative point of view, are given here. The present method is adapted from that of Adkins,1 which in turn was based upon those of Mignonac,2 von Braun and coworkers,3 and Mailhe.4 Benzyl cyanide has been converted to the amine by catalytic reduction with palladium on charcoal,5 with palladium on barium sulfate,6 and with Adams catalyst 7 by chemical reduction with sodium and alcohol,8 and with zinc dust and mineral acids.9 Hydrocinnamic acid has been converted to the azide and thence by the Curtius rearrangement to /3-phenyl-ethylamine 10 also the Hofmann degradation of hydrocinnamide has been used successfully.11 /3-Nitrostyrene,12 phenylthioaceta-mide,13 and the benzoyl derivative of mandelonitrile 14 all yield /3-phenylethylamine upon reduction. The amine has also been prepared by cleavage of N- (/3-phenylethyl) -phthalimide 15 with hydrazine by the Delepine synthesis from /3-phenylethyl iodide and hexamethylenetetramine 16 by the hydrolysis of the corre-... 

The variety of reaction products can be demonstrated by the following examples. Alcohols usually form with platinum oxide catalysts e.g., in the case of furfuryl alcohol with Adams catalyst in ethanol, at least seven reaction products are obtained ... 

Aldehydes are easily hydrogenated to alcohols but ketones are more difficult to reduce because of steric hindrance. Hydrogenolysis is a problem with the catalytic reduction of carbonyls, particularly when linked to aromatic systems. Pd and H2 reduce alkenes faster than carbonyls. Metal catalyst Pt is commonly used for the reduction of carbonyls. For example, the Adams catalyst (Pt02) reduces 2-naphthaldehyde (6.31) to 6.32 in 80% when used with FeCls as a promoter. When excess of the promoter is used the product is 2-methylnaphthalene (6.33), which is also obtained by the reduction of 6.31 with Pd on BaS04 and H2. 

Naphthalene is reduced to 1,4-dihydronaphthalene by sodium and alcohol. Isomerization of this product to 3,4-dihydronaphthalene occurs with sodamide in liquid ammonia. Tetrahydronaphthalene (tetralin) is formed from naphthalene by sodium in amyl alcohol or by reduction with nickel-aluminum alloy and aqueous alkali. Catalytic hydrogenation of naphthalene can be stopped at the tetralin stage over copper chromite, Raney nickel, or alkali metal catalysts. cis-Decahydronaphthalene is produced by high-pressure hydrogenation of tetralin over Adams catalyst, whereas a mixture of cis- and trans-decalins is obtained from naphthalene under the same conditions. ... 

Various ketones have been converted to optically active alcohols with high optical purity and in high yield using alcohol dehydrogenases. In addition, successful reductions have been performed by catalytic hydrogenation, over Adams catalyst, " Raney nickel, and palladium on carbon, and lithium in tcrf-butyl alcohol/ammonia, and in one case even with lithium dibutylcuprate. ... 

When reduced with sodium amalgam in absolute alcohol, compound 96 yielded a crystalline product with molecular formula C22H33NO4. On the basis of mass spectral and IR data as well as the formation of a diacetate derivative, structure 98 was assigned to this reduction product. Hydrogenation of compound 96 with Adams catalyst afforded compound 99. 

A catalyst prepared as a suspension by warming diloroplatinic acid and an organosilicon hydride such as triethylsilane in 95 /o-ethanol is remarkably stable on storage and in many cases more active than Adams catalyst Diisobutyl aluminum hydride has been found to be an excellent reagent for the selective reduction of 2-en-l-ones and 2-ene-l,4-diones to the corresponding alcohols . Nickel boride catalysts have been recommended for the hydrogenation of strained carbon-... 

Reactions catalysed by Adams catalyst can be carried out in alcoholic solution which is sometimes enhanced by the presence of HCl a variety of other organic solvents have been used which include EtOAc, EtOAc+15% AcOH, EtOAc+8%EtOH, and glacial AcOH and neat CF3CO2H is a particirlarly good solvent for the reduction of C=N in heterocyclic compounds. 

This is carried out by reduction with hydrogen in the presence of Pt02 (Adams catalyst) or palladium on a carrier (26) in ethanol. After filtering off the catalyst, the solution is worked up best by evaporating alcohol after the addition of acetic acid. The residue can be worked up immediately by acetylating it with acetic anhydride. The reduction of nitro groups takes place easily even in the case of dinitro compounds and nitrophenols. 

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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