Sodium amalgam applications

This synthetic sequence for an olefin synthesis has been further developed by Kocienski who has shown that eliminative desulphonylations carried out on / -acyloxysulphones are remarkably stereoselective for the synthesis of trans-disubstituted-olefins. The method has wide applicability in that a-lithio phenyl sulphones are readily generated, and are readily coupled to aldehydes or ketones, to give j8-hydroxysulphones. The hydroxyl function of these is then esterified and the synthesis is completed by the reductive elimination with sodium amalgam. Kocienski has prepared two reviews that summarize his syntheses of a range of natural products - one of which is diumycinoP obtained... 

This is by far the most important reaction of tetrazolium salts and accounts for the bulk of their many applications. A large variety of reagents can reduce tetrazolium salts, e.g., 53 to formazans, e.g., 51. Ascorbic acid, hydrazine, and hydroxylamine have been recommended for the preparation of formazans from tetrazolium salts.245 Stronger reducing agents such as ammonium sulfide, sodium amalgam, sodium dithionite, and catalytic hydrogenation can further reduce the formazans to the amidrazones, e.g.,... 

The pK.d values of TV-methyltrifluoromethanesulfonamide (TfNHMe = 7.5) and TV-meth-yltoluenesulfonamide (TosNHMe= 11.7) have been examined and it was found that these sulfonamides are applicable to the Mitsunobu reaction conditions. 80 A modified Mitsunobu reaction has been used for the synthesis of A7"-alkyl amino acid esters 81,82 this method is only applicable to amino acid esters and not to the free acids. Thus, TV-Tos amino acid esters are condensed with MeOH, EtOH, or iPrOH in the presence of TPP and DEAD. The Tos group is deprotected by sodium in liquid ammonia or with sodium amalgam. 83 The deprotection of the Tos group has also been achieved electrochemically under mild conditions and in good yields. 84 ... 

Reaction LXVI. (a) Redaction of Unsaturated Acids by means of Sodium Amalgam in Alkaline Solution. (A., 121, 375 137, 237.)—The preparation below illustrates an important application of sodium amalgam, this substance being especially useful for reducing groups or double bonds in compounds containing carboxyl, as the alkali present keeps the substance in solution and protects the acid group. 

On the other hand, application of alkali metal amalgam permits the slowing down of the reaction of metals with alcohols, which is used in the industrial production of alkali metals alkoxides. Production of NaOR by Mathieson Alkali Works is based, for instance, on the reaction of sodium amalgam (formed as a result of the electrolysis of aqueous NaCl solution with the mercury cathode) with alcohol NaOR ROH is isolated from the solutions. Na residue in the amalgam is hydrolyzed, the obtained mixture is returned to the electrolyz-... 

Allylic alcohols from sulfones.1 Polish chemists have extended the Julia synthesis of alkenes (11, 474) to a synthesis of allylic alcohols. In the presence of 1 equiv. of BF3 etherate, a-alkoxy aldehydes react with lithiafed sulfones to form adducts that are converted to allylic alcohols on reduction with sodium amalgam. This reaction was developed specifically for a synthesis of prostaglandins from Corey s lactone-aldehyde, but should have wider application. 

The Marckwald synthesis116 employed the reaction of a-amino-ketones with cyanates, thiocyanates, and isothiocyanates to yield 3 -imidazol-2-ones or AH-imidazole-2-thiones which are readily converted into imidazoles. The chief limitation of this method, which has been discussed adequately in earlier reviews,1-3 is in the synthesis of the a-aminocarbonyl compounds. The most convenient procedure is by reduction with sodium amalgam of a-amino acids.117 Among recent applications of the method118 119 is the synthesis118 of 4,5-... 

Metal carbonyls are reduced by a variety of reagents, of which sodium amalgam is the most common, to produce air-sensitive low-valent anionic complexes. These anions vary widely in nucleophilicity and by far the greatest use has been made of the most nucleophilic, [Fe(CO)2(t/ -CjH5)]". However, [M(CO),] (M = Mn, Re), [M(CO)J- (M = Co, Ir), [M(CO)3( -C5Hj)]- (M = Cr, Mo, W), [V(CO)J- and [Fe(CO)4] have all found limited application. Examples are collected in Table 1. In general, fast, ionic reactions ... 

Sodium amalgam is employed in the manufacture of sodium hydroxide sodium—potassium alloy, NaK, is used in heat-transfer applications and sodium—lead alloy is used in the manufacture of tetraethj ead and tetramethyllead, and methylcyclopentadienyknanganesetricarbonji, a gasoline additive growing in importance for improving refining efficiency and octane contribution. 

A few examples of the reduction of aliphatic diazo compounds to hydrazines exist," but this is not a generally applicable method for the synthesis of alkylhydrazines. On the other hand, arylhydrazines can be prepared by reduction of aromatic diazonium salts.The most commonly used reagents for this conversion are sulfur dioxide (or sodium sulfite) and tin(II) chloride, these being used to reduce arenediazo-nium chlorides in aqueous solution. Several other reagents, including sodium amalgam and triphenylphosphine, have been used for specific reductions of this type. Arenediazonium tetrafluoro-borates have been reduced to the correspwnding hydrazinium salts (3) by benzeneselenol in dichloro-... 

The reduction of the p-acyloxy sulfone is most often carried out with sodium amalgam, as the examples below indicate. The reductive elimination can be buffered with disodium hydrogenphosphate for sensitive substrates. In certain applications it has proven advantageous to utilize lithium or sodium in ammonia. For example, Keck s synthesis of pseudomonic acid C made use of the lithium/ammonia reductive elimination to simultaneously form an alkene and deprotect a benzyl ether.In studies directed toward the same target, Williams made use of a reductive elimination procedure developed by Lythgoe, involving the formation of the xanthate ester followed by reduction with tri-n-butyltin hydride. ... 

Several types of chemical reduction performed on pyrimidine nucleosides may have application to the pyrimidine nucleotides. For example, sodium amalgam in dilute acetic acid has been used for converting thymidine and 2 -deoxyuridine into a mixture of reduced derivatives, from which... 

The first synthesis, that of eri/fftro-tetrodialdose, was made by Wohl and Mylo, starting from acetylene. The basis of the method employed (both here and in the further syntheses of this dialdose) is the hydroxylation of malealdehyde or a derivative of the latter. The next method introduced was Uenzelmann s application of catalytic reduction by the Rosenmund procedure to tetra-O-acetylmucyl dichloride he thus obtained the corresponding tetraacetate of gaZacto-hexodialdose. By this procedure, the only known heptodialdose has also been prepared. Another reduction procedure, controlled reduction of D-glucurono-6,3-lactone with borohydride or sodium amalgam, was used by MacDonald and H. O. L. Fischer and by F. G. Fischer and Schmidt. ... 

A generally applicable method of preparing dialkyl- and diaryl-mercury compounds is by treatment of alkyl or aryl halides or alkyl sulfates with sodium amalgam 160... 

Ruthenium complex 33 has been prepared by thermolysis as shown in Scheme 1 for early transition metals [25]. However, this procedure is not applicable to nickel, platinum and palladium complexes because they undergo reductive elimination, rather than beta elimination. Complexes 31 and 32 have been prepared by sodium amalgam reduction of the corresponding a-complex 37, as shown in Scheme 6 [6,7,24]. 

In many of the applications of this chemistry, the identity of the cation is not important, and so we consider the use of sodium amalgam only. The classical summary of industrial amalgam chemistry is that of MacMullin [167], and we shall follow his treatment here. 

This reaction, preceded by the formation of Hg[Co(CO)4]2 from sodium amalgam and dicobalt octacarbonyl in a hydrocarbon solvent, is the basis of a recently proposed method for the purification of mercury 37). However, the cost of dicobalt octacarbonyl makes the widespread application of this mercury purification method unlikely. Treatment of Hg[Co(CO)4]2 with trimethylphosphite also liberates mercury, producing the nonionic derivative [Co(CO)3P(OCH3)3]2 rather than a salt 26)... 

The method was also used for the determination of cysteine and glutathi but its application presents, mainly in biological materials, the doubts expressed in the previous paragraphs. For the determination of cystine a method is employed based on the reduction of cystine in an acidic medium with sodium amalgam or on the reaction with sulphite at pH 8-12 according to equation ... 

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