Aluminum amalgam preparation

Aluminum amalgam, prepared by Wislicenus method,28 and moist ether are usually used, being allowed to react with the unsaturated compound for 1-2 days with occasional addition of a little water. 

Benzopinacol has been prepared by the action of phenylmag-nesium bromide on benzil 1 or methyl benzilate. Usually it has been obtained by reduction of benzophenone, the reducing agents being zinc and sulfuric acid or acetic acid, aluminum amalgam, and magnesium and magnesium iodide. The present... 

I. Amalgamated aluminum is prepared as follows Aluminum turnings, freed from any oil by washing with ether, are stirred... 

Reductions with aluminum are carried out almost exclusively with aluminum amalgam. This is prepared by immersing strips of a thin aluminum foil in a 2% aqueous solution of mercuric chloride for 15-60 seconds, decanting the solution, rinsing the strips with absolute ethanol, then with ether, and cutting them with scissors into pieces of approximately 1 cm [141,142]. In aqueous and non-polar solvents aluminum amalgam reduces cumulative double bonds [143], ketones to pinacols [144], halogen compounds [145], nitro compounds [146, 147], azo compounds [148], azides [149], oximes [150] and quinones [151], and cleaves sulfones [141, 152, 153] and phenylhydrazones [154] (Procedure 30, p. 212). 

Nitroso compounds are usually not obtained directly but rather by reoxidation of hydroxylamino compounds or amines. Hydroxylamino compounds are prepared by electrolytic reduction using a lead anode and a copper cathode [573], by zinc in an aqueous solution of ammonium chloride [574 or by aluminum amalgam [147], generally in good yields. 

Reduction of oximino esters, i.e. oximes of keto esters, is very useful for the preparation of amino esters. Reductions are very selective since the oximes are easily reduced by catalytic hydrogenation over 10% palladium on carbon in ethanol (yield 78-82%) I094, by aluminum amalgam in ether (yields 52-87%) [750, 70P5], or by zinc dust in acetic acid (yield 77-78%). None of these reagents attacks the ester group. The last mentioned reaction gives an N-acetyl derivative [1096. ... 

In 1825, however, he studied the chemical action of the voltaic current, and tried to isolate chemically the metal believed to be present m alumina. He first prepared liquid aluminum chloride by passing a current of chlorine gas over a mixture of charcoal and alumina heated to redness. By allowing potassium amalgam to react with the aluminum chloride, he prepared an aluminum amalgam, and by distilling off the mercury out of contact with the air, he obtained a metal that looked like tin (11). 

The oximes of 4,5,6,7-tetrahydrobenzo[6]thiophen-4-one and -7-one undergo the Beckmann rearrangement to give 146 354 451 and 147 (R = H),362 respectively. Compound 147 (R=C1) may be prepared similarly and by treating 2-chloro-4,5,6,7-tetrahydrobenzo[ ]thio-phen-7-one with ammonia in the presence of PPA.356 The oxime of 4,5,6,7 -tetrahydrobenzo [6]thiophene- 4-one affords 4-aminobenzo [6]-thiophene in a modified Leuckart reaction.241,355 The same oxime may be converted into 4-amino-4,5,6,7-tetrahydrobenzo[ ]thiophene by reduction with aluminum amalgam in methanol.452 The parent ketone also affords 4-amino-4,5,6,7-tetrahydrobenzo[6]thiophene on reaction with formamide at 165°, followed by acidic hydrolysis of the resulting 4-formylamino compound.355... 

The only practical method for the preparation of pinacol hydrate is the reduction of acetone and the procedure described above is a modification of that of Holleman.1 The more common reducing agents that have been used are magnesium amalgam,2 aluminum amalgam,3 sodium,4 and sodium amalgam.5 Electrolytic reduction has also been used.6 1 Rec. trav. chim. 25, 206 (1906). 

Although the first preparation of pentacene reported by Clar in 1929 proceeded by the dehydrogenation of a difficult to prepare precursor molecule (9, Scheme 3.1) [23], most modern syntheses of pentacene and its end-functionalized derivatives proceed via the reduction of pentacenequinones, typically by the action of aluminum amalgam in cyclohexanol (Scheme 3.2) [24]. 

Sponge Nickel Catalyst is typically used in the manufacture of amines and polyols. It is prepared by chemically treating a Nickel-aluminum amalgam with sodium hydroxide to remove... 

The aldehyde is also obtained by the hydroformylation of allylbenzene.6 An alternative method involves benzylation of 2-ethylthiazoline followed by reduction with aluminum amalgam and cleavage with mercuric chloride.( A sixth method of preparation is the phenylation of 2-vinyl-5,6-... 

The reactivity and chemistry of tetrahydro-3,6-pyridazinediones has not been much investigated. The parent compound (cyclic succinhydrazide) has been obtained by aluminum amalgam reduction of maleic hydrazide. Attempts to prepare it by alternative methods were unsuccessful (Section III,D). It forms a A,A-dimethyl or diacetyl and a A-monoethyl derivative with benzenesulfonyl... 

The reduction of aldols and ketols from the aldol condensation (method 102) is often a convenient route to branched 1,3-dio/s. Catalytic hydrogenation over platinum oxide, nickel-on-kieselguhr, and copper-chromium oxide has been used. Other procedures include electrolytic reduction and reduction by aluminum amalgam. 1,3-Diols may also be prepared by catalytic reduction of 1,3-diketones. Cleavage of the carbon-to-carbon and carbon-to-oxygen bonds accompanies this conversion. The effect of structure on the course of the reaction has been studied. ... 

This reaction has found little application to mercaptan syntheses since the mercaptans are usually as readily available (by other methods) as the disulfides. The S-S linkage is reduced by zinc in acetic or sulfuric " acid, lithium aluminum hydride, or metallic sodium. y-Hydroxy-propyl disulfide is reduced electrolytically in 70% yield. Reduction by sodium disulfide does not reduce the nitro group in the preparation of p-nitrothiophenol (65%), whereas zinc and acetic acid converts o-nitro-phenyl disulfide to o-aminothiophenol (90%). Disulfides made by the action of ammonium hydrogen sulfide on aldehydes are sources for difficultly available aromatic and heterocyclic mercaptans. The disulfides are reduced by aluminum amalgam and water. ... 

Certain aliphatic diamines have been prepared by reduction of nitro amines with hydrogen or aluminum amalgam. The starting materials are readily obtained by the reaction of nitroparaffins with formaldehyde and amines (method 444). 

The earliest method of this type, developed by Marckwald, employed the reaction of a-aminocarbonyl compounds (or their acetals) with cyanates, thiocyanates or isothiocyanates to give 3//-imidazoline-2-thiones. These compounds can be converted readily into imidazoles by oxidation or dehydrogenation. The major limitations of this synthetic procedure are the difficulty of synthesis of a wide variety of the a-aminocarbonyl compounds, and the limited range of 2-substituents which are introduced. The reduction of a-amino acids with aluminum amalgam provides one source of starting materials. The method has been applied to the preparation of 4,5-trimethyleneimidazole (83) from 2-bromocyclopentanone (70AHC(12)103), and to the synthesis of pilocarpine (84 Scheme 47) (80AHC(27)24l). If esters of a-amino acids react with cyanates or thiocyanates, the products are hydantoins and 2-thiohydantoins, respectively. 

Aldol-Type Addition. Aldol-type addition of the magnesium enolate of (R)-(+)-7-butyl 2-(p-tolylsulfinyl)acetate, prepared with 7-butylmagnesium bromide, with aldehydes and ketones afforded, after desulfurization with Aluminum Amalgam, p-hydroxy esters in very high diastereoselectivity (eq Two chiral centers are created in the first step with very high diastereoselectivity (mainly one diastereomer is formed). A model M based on the structure of the sulfinyl ester enolate (determined by C NMR) and on electrophilic assistance of magnesium to the carbonyl approach, was proposed to explain and predict the absolute configuration of the two created chiral centers. ... 

Aldol-Type Condensation. The aldol-type condensation of the enolate anion of sulfinylpropionate, which was prepared as usual with the base t-butylmagnesium bromide, with aldehydes afforded after desulfurization with Aluminum Amalgam the corresponding 3-hydroxy esters in high yield (90%) and, with aliphatic aldehydes, high diastereoselectivity (eq 3). The amount of asymmetric induction was determined by transformation of the 3-hydroxy esters to the corresponding isopropyl-substituted alcohols. 

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