Tetralin reduction

A remarkable feature of the Birch reduction of estradiol 3-methyl ether derivatives, as well as of other metal-ammonia reductions, is the extreme rapidity of reaction. Sodium and -butyl alcohol, a metal-alcohol combination having a comparatively slow rate of reduction, effects the reduction of estradiol 3-methyl ether to the extent of 96% in 5 minutes at —33° lithium also effects complete reduction under the same conditions as is to be expected. Shorter reaction times were not studied. At —70°, reduction with sodium occurs to the extent of 56 % in 5 minutes, although reduction with lithium is virtually complete (96%) in the same time. (The slow rates of reduction of compounds of the 5-methoxytetralin type is exemplified by 5-methoxy-tetralin itself with sodium and f-butyl alcohol reduction occurs to the extent of only 50% in 6 hours vs. 99+% with lithium.) The iron catalyzed reaction of sodium with alcohols must be very fast since it competes so well with the rapid Birch reduction. One cannot compensate for the presence of iron in a Birch reduction mixture containing sodium by adding additional metal to extend the reaction time. The iron catalyzed sodium-alcohol reaction is sufficiently rapid that the aromatic steroid still remains largely unreduced. 

A modification of the preceding preparation employs ethylenediamine as a convenient nonvolatile solvent and Tetralin as the commercially available starting material. The results of the reduction are essentially identical. 

As previously described, a mixture of and J -octalins can be prepared by the reduction of naphthalene or Tetralin. Another route to this mixture is the dehydration of a mixture of 2-decalol isomers. This latter route has certain advantages in that one can avoid the handling of lithium metal and low-boiling amines. Moreover, 2-decalol is available commercially or can be prepared by the hydrogenation of 2-naphthol (5). In either case a comparable mixture of octalins is obtained, which can be purified by selective hydroboration to give the pure J -octalin (Chapter 4, Section III). 

Autoxidation may in some cases be of preparative use thus reference has already been made to the large-scale production of phenol+ acetone by the acid-catalysed rearrangement of the hydroperoxide from 2-phenylpropane (cumene, p. 128). Another example involves the hydroperoxide (94) obtained by the air oxidation at 70° of tetrahydro-naphthalene (tetralin) the action of base then yields the ketone (a-tetralone, 95), and reductive fission of the 0—0 linkage the alcohol (a-tetralol, 96) ... 

Additionally, it has been noted that Tetralin operates via hydride transfer, at least in its reduction of quinones. Thus it has been shown that Tetralin readily donates hydrogen to electron-poor systems, such as quinones at 50°-160°C. The reaction is accelerated by electron-withdrawing substituents on the H-acceptor and polar solvents, and is unaffected by free radical initiators (6). These observations are consistent with hydride transfer, as is the more recent finding of a tritium isotope effect for the reaction (7). 

H2 + CH4, D2, P2 + Tetralin, GO + H2O were selected and reduction was conducted by varying the reaction time. Each isolated fraction was subjected to ultimate analysis, H-NMR, C-13 NMR, molecular weight measurement and the structural parameters were calculated. The results of the study of these structural parameters in the course of the reactions were evaluated and the reaction mechanisms thereof are discussed below. 

Reduction of tetralin to octalin with lithium and ethylenediamine proceeds slowly, but if heated to 85°C it becomes violent, with rapid evolution of hydrogen. 

An investigation of different organic solvents, buffer, surfactants, and organorhodium compounds established that the catalytic reduction of tetralin using [ Rh(l,5-hexadiene)Cl 2] proceeds with high efficiency at high substrate-to-catalyst ratios. The reaction occurs at r. t. and 1 atm. pressure in a biphasic mixture of hexane and an aqueous buffer containing a low concentration of a surfactant which stabilizes the catalysts.314... 

Partial reduction of polyarenes has been reported. Use of boron trifluoride hydrate (BF3 OH2) as the acid in conjunction with triethylsilane causes the reduction of certain activated aromatic systems 217,262 Thus, treatment of anthracene with a 4-6 molar excess of BE3 OH2 and a 30% molar excess of triethylsilane gives 9,10-dihydroanthracene in 89% yield after 1 hour at room temperature (Eq. 120). Naphthacene gives the analogously reduced product in 88% yield under the same conditions. These conditions also result in the formation of tetralin from 1-hydroxynaphthalene (52%, 4 hours), 2-hydroxy naphthalene (37%, 7 hours), 1-methoxynaphthalene (37%, 10 hours), 2-methoxynaphthalene (26%, 10 hours), and 1-naphthalenethiol (13%, 6 hours). Naphthalene, phenanthrene, 1-methylnaphthalene, 2-naphthalenethiol, phenol, anisole, toluene, and benzene all resist reduction under these conditions.217 Use of deuterated triethylsilane to reduce 1-methoxynaphthalene gives tetralin-l,l,3-yielding information on the mechanism of these reductions.262 2-Mercaptonaphthalenes are reduced to 2,3,4,5-tetrahydronaphthalenes in poor to modest yields.217 263... 

Methoxytetralin [Partial Reduction of a Substituted Naphthalene to a Tetralin].262 1,5-Dimethoxynaphthalene (300 mg, 1.0 mmol) dissolved in... 

Methoxytetralin, substituted naphthalene reduction to tetralin, 132-133 Methyl-2-(phenylcarbamoyl)butanoate, a,-unsaturated ester hydrocarbamoylation, 134 4-Methylbenzyl chloride [reductive... 

Tetrahydropyran (THP), aldehyde etherification, 67-68 Tetralin compounds, 5-methoxytetralin reduction of substituted naphthalene, 132-133... 

Our initial conclusion from the FT-IR data on the residua is that it is the reduction in the carboxyl concentration which is most important to the improvements brought about by preliquefaction, and this reduction requires the catalyst but not the solvent and probably not the hydrogen. The major reasons for these conclusions are 1) pretreatments dry, with naphthalene (with hydrogen and nitrogen) and with tetralin, all reduced the carboxyl concentration, and the dry and naphthalene cases both produced improved liquefaction yields 2) the presence of hydrogen does not appear to make much difference between HC 1401-350 and NC 1401-350 and 3) the increased aromatics were not present in the dry preliquefaction residue (HCD 1401-350) and so, do not appear necessary for the improvement in liquefaction. 

Many reductions with sodium are carried out in boiling alcohols in methanol (b.p. 64°), ethanol (b.p. 78°), butanol (b.p. 117-118°), and isoamyl alcohol (b.p. 132°). More intensive reductions are achieved at higher temperatures. For example reduction of naphthalene with sodium in ethanol gives 1,4-dihydronaphthalene whereas in boiling isoamyl alcohol tetralin is formed. 

The effect of operating variables on the electrochemical reduction of tetralin used as a model compound for the hydrogenation of coal is described. The effect of adding a proton donor (fort-butyl alcohol) on the reduction of an olefin was also investigated. 

Reduction of 1-decene had to be carried out at a lower concentration (0.073M) since decene was not completely soluble at the concentrations used in the case of tetralin (0.22M). Electrolysis was interrupted after 0.0062 Faradays were passed through the solution, corresponding to 42.2% conversion of 1-decene to decane at 100% current efficiency. In these runs, a carbon cathode was used. Current efficiency for reducing 1-decene was 27.3%. In the presence of an equimolar amount of terf-butyl alcohol (0.073M), the current efficiency for 1-decene was 38.6%, corresponding to a 41% increase. 

Based on results of electrochemical reductions of tetralin in ethylenediamine, current efficiency is highest with aluminum as cathode material and with lithium chloride as electrolyte. A substantial increase in current efficiency was obtained in reducing 1-decene by adding a proton donor. 

Dr. Sternberg No kinetic measurements were carried out with coal. We did carry out measurements with tetralin using lower lithium chloride concentrations and found a marked decrease in the rate of reduction. However, interpreting the results will have to await perfection of a better technique (now under study) for carrying out these reductions at a controlled potential. 

Reduction of arenes.1 Raney nickel (Mozingo type) in combination with 2-propanol (reflux) effects reduction of aromatic rings in 2-18 hours. Naphthalene is reduced in 18 hours to tetralin (90% yield) and cis- and frans-decalin (10% yield). Anisole is reduced in 110 hours to cyclohexyl methyl ether (90% yield). Nitrobenzene is reduced quickly to aniline and then further to cyclohexylamine and cyclohexylisopropylamine. 

Naphthalene can be reduced more easily than benzene. With sodium in alcohol, 1,4-dihydronaphthalene is formed. Catalytic hydrogenation gives tetralin (1,2,3,4-tetrahydronaphthalene). Further reduction to give perhydro-naphthalene (decalin) can be achieved on prolonged catalytic hydrogenation at relatively high temperatures and pressures ... 

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