Magnesium amalgams

Magnesium amalgam. Mainly used for removing traces of water from alcohols by refluxing the alcohol in the presence of the Mg amalgam followed by distillation. 

Hyponitrites can be prepared in variable (low) yields by several routes of which the commonest are reduction of aqueous nitrite solutions using sodium (or magnesium) amalgam, and condensation of organic nitrites with hydroxylamine in NaOEt/EtOH ... 

Scheme 5.13 provides several examples of reductive carbon-carbon bond formation, including formation of diols, alkenes, and acyloins. Entry 1 uses magnesium amalgam in the presence of dichlorodimethylsilane. The role of the silane may be to... 

Addition of zirconocene to unsymmetric acetylenes is often regiospe-cific. Thus the reaction of 1-trimethylsilyl-l-propyne (50) with zirconocene dichloride and magnesium amalgam gives the zirconocycle 51, where the large trimethylsilyl groups are adjacent to zirconium.21 Iodination of 51 affords diiodide 52, which has been converted to the corresponding di-stibaferrocene 55 and dibismaferrocene 56. 

Korneev, M. I., 1955, Pool Boiling Heat Transfer with Mercury and Magnesium Amalgams, Teploener-getika 2 44. (2)... 

Reductive coupling of imines 43 (R1 = Me, Ph or 2-pyridyl R2 = Me, Pr, t-Bu or PI1CH2) in THF under the influence of a low-valent titanium species, produced by the action of magnesium amalgam on titanium(IV) chloride, gave the DL-diamines... 

Somewhat less frequent than the reductions of aliphatic ketones to secondary alcohols and to hydrocarbons are one-electron reductions to pinacols. These are accomplished by metals such as sodium, but better still by magnesium or aluminum. Acetone gave 43-50% yield of pinacol on refluxing with magnesium amalgam in benzene [140], and 45% and 51% yields on refluxing in methylene chloride or tetrahydrofuran, respectively [825. ... 

These dimerizations are analogous to those of the radical anions R2C - 0 which are intermediates in the reduction of ketones to pinacols. Indeed, in the presence of magnesium amalgam, pyridine... 

The methods for producing diacetone alcohol are the action of barium hydroxide on acetone 1 the action of calcium hydroxide on acetone 2 the action of concentrated sodium hydroxide or potassium hydroxide on acetone 3 the action of magnesium amalgam on acetone 4 and the action of nitrous acid on diace-tonamine.5 The last method was not considered because of the difficulty of preparing diacetonamine. Of the methods employing acetone only, the first two seemed more promising, since the others are reported as giving low yields of impure product. It was soon found that barium hydroxide acted more rapidly than calcium hydroxide (as reported by L. P. Kyriakides) and this method was therefore employed. 

It is worth noting that if the aldol condensation takes place in the presence of magnesium amalgam, the aldehydic group is simultaneously reduced and a 1 3-dihydric alcohol is formed. 

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). 

One popular way to perform the reaction is to use magnesium amalgam as this avoids the formation of anions indeed the magnesium atom holds the two radicals together 36 so that the dimer... 

Drop a small lump of magnesium amalgam into a test tube of cold water. A violent reaction takes place. A gas... 

These dimerizations are analogous to those of the radical anions R2C 0 which are intermediates in the reduction of ketones to pinacols. Indeed, in the presence of magnesium amalgam, pyridine condenses with acetophenone to give alcohol 396 by oxidation of the intermediate dihydropyridine. In a similar reaction type, pyridine with zinc and acetic anhydride or ethyl chloroformate yields (397 R = Me or OEt, respectively). 

CH2Br2 N [20] Di-Grignard reagent obtained using magnesium amalgam in diisopropyl ether, and vacuum line technique. Yield 80%... 

It has been used particularly to prepare samples for physicochemical studies [125-127], The reaction may be carried out in the absence of solvent, in which case the product is extracted from the magnesium amalgam formed by a suitable solvent [128, 129], In a solvent such as diethyl ether the reaction may be very slow, but proceeds in virtually quantatitive yield [130, 131],... 

There is a patent claiming that magnesium amalgam reduced [RhCl(PPh3)3] to [Rh(PPh3)2]2.41 However, since the high field H NMR spectra of these complexes have not been obtained, there... 

Several experimenters 3 advocate preparing pure hydrogen by the interaction of aluminium-amalgam or magnesium-amalgam and water, and consider the method very convenient ... 

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