Reductions Using Aluminum Amalgam

164 gms of p-methoxybenzyl-methyl-ketone, 2500 ccs. of ether, 500 CCS. of methanol, 100 ccs. of 40 % aqueous methylamine solution and 100 gms. of activated aluminium turnings are stirred for 6 to 7 hours with occasional slight warming. On completion of the conversion the mixture is filtered and the resulting base B-(/ -methoxyphenyl)-isopropylmethylamine separated from the solution by adding dilute acid thereto. On adding alkalies the free base is obtained in the form of an oil. Source Knoll 1938 

Replacement of P-2-P with phenylacetaldehyde produces pheny lethy lamine. 

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B. N-t-Butylhydroxylamine. Caution Since hydrogen may he liberated during the reduction with aluminum amalgam, the reaction should he conducted in a hood. Also, the aluminum amalgam may he pyrophoric. Consequently, it should he used, immediately and not allowed to become dry. 

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. ... 

Metal-induced reductive dimerization of carbonyl compounds is a useful synthetic method for the formation of vicinally functionalized carbon-carbon bonds. For stoichiometric reductive dimerizations, low-valent metals such as aluminum amalgam, titanium, vanadium, zinc, and samarium have been employed. Alternatively, ternary systems consisting of catalytic amounts of a metal salt or metal complex, a chlorosilane, and a stoichiometric co-reductant provide a catalytic method for the formation of pinacols based on reversible redox couples.2 The homocoupling of aldehydes is effected by vanadium or titanium catalysts in the presence of Me3SiCl and Zn or A1 to give the 1,2-diol derivatives high selectivity for the /-isomer is observed in the case of secondary aliphatic or aromatic aldehydes. 

Aluminum. Reductions with aluminum are not commonly found, however, I have included the preparation of the amalgam. Aluminum can be used to reduce aromatic nitro compounds (Org, Syn., 52, 77(1972). 

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. 

For the reduction to pinacols aluminum amalgam [825] or low valence state titanium chloride [207] were used. Under different conditions the titanium... 

Metal amalgams may be used for reduction of the keto groups in keto esters provided the medium does not cause hydrolysis of the ester. Because of that aluminum amalgam in ether is preferable to sodium amalgam in aqueous solutions. Diethyl oxalacetate was reduced to diethyl malate by sodium amalgam in 50% yield and with aluminum amalgam in 80% yield [148], Stereospecific reduction of a- and fi-keto esters to optically pure hydroxy esters was achieved by biochemical reduction in moderate to good yields. Saccharomyces cerevisiae converted methyl 2-keto-2-phenylacetate to methyl... 

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. ... 

Strontium metal also can be prepared by thermal reduction of its oxide with aluminum. Strontium oxide-aluminum mixture is heated at high temperature in vacuum. Strontium is collected by distillation in vacuum. Strontium also is obtained by reduction of its amalgam, hydride, and other salts. The amalgam is heated and the mercury is separated by distillation. If hydride is used, it is heated at 1,000°C in vacuum for decomposition and removal of hydrogen. Such thermal reductions yield high—purity metal. 

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). 

Reduction of [Mo(CO)2(bpy)2] using sodium amalgam or sodium naphthalenide gives paramagnetic [Mo(CO)2(bpy)2] in dimethoxyethane (81JOM(218)C31). Oxidation of [Mo(CO)2(bpy)2] using silver tetrafluoroborate in acetonitrile or aluminum chloride in methylene chloride and followed by sodium tetrafluoroborate gives... 

Reductive desulfurization of 9-(phenylsulfonyl)furo[2,3- ]quinoline and its 2-methyl derivative can be effected by treatment with LAH in THF solution at reflux, but proceeded poorly with aluminum amalgam, the reagent of choice for the reductive cleavage of vinyl sulfones <83JOC774>. Raney nickel was used to remove a thiomethyl substituent from the central ring of a furochromone direct precursor to visnagan <89JOC448l>. 

Reduction reduction of quinazolines to 3,4-dihydroquinazolines proceeds without much difficulty, especially when the quinazolines arc not substituted at C4. Under forcing conditions using sodium amalgam, sodium/alcohol, lithium aluminum hydride, and sometimes metal/acid reagent or electrolytic reduction, 1,2,3,4-tetrahydroquinazolincs may be formed. 

Sulfinyl and sulfonyl groups are easier to reduce than a-(aikylthio)carbonyl compounds. Aluminum amalgam has frequently been used for removal of sulfinyl and sulfonyl groups. This reagent is typically used in refluxing (wet) THF reduction of 3-keto sulfones can be carried out at room temperature by Na(Hg)x, if the solution is buffered with Na2HP04 ... 

The reduction of cinnamylidene fluorene by aluminum amalgam in moist ether to 1-fluorenyl-3-phenyl-l-propene (I), a 1,4-addition, exemplifies the use of Al(Hg) rather than Na(Hg) for the reduction of alkali-sensitive compounds in the presence of Na(Hg), I might be tautomerized to 3-phenyl-1-propylidene fluorene [26]. Another example is the reduction of a cumulene, l,l,6,6-tetraphenyl-l,2,3,4,5-hexapentaene, to 1,1,6,6-tetraphe-nyl-l,2,4,5-hexatetraene by Al(Hg) [27]. 

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