Zinc Amalgam reduction with

By application of the Clemmensen reduction,aldehydes and ketones 1 can be converted into the corresponding hydrocarbons 2. As the reducing agent zinc amalgam, together with concentrated hydrochloric acid or gaseous hydrogen chloride, is used. 

The compound [(i7s-CsHs)Cr(NO)2] 2 was first prepared in low yields (<5%) by the reduction of (i75-CsHs)Cr(NO)2Cl with sodium tetrahydroborate in a two-phase water-benzene system.6 Recently, this complex was isolated in 75% yield from the zinc amalgam reduction of (i7s-C5Hs)Cr(NO)2Cl in tetrahydrofuran over a period of 21 hours.2 However, [07s-CsH5)Cr(NO)2]2 is synthesized most conveniently by the reduction of the above-mentioned chloro complex with sodium amalgam in benzene as outlined below. 

When the reactions of pyrroles and indoles with aldehydes are catalyzed by hydriodic acid, the initially formed carbinols or azafulvenes are reduced to yield the corresponding alkylpyrroles and alkylindoles (68CJC3291,70CJC139). The reductive alkylation of the pyrrole ring, using a range of aliphatic and aromatic aldehydes and ketones, may also be accomplished with phosphonium iodide, with hydrochloric acid and zinc amalgam, or with tin(II) bromide in hydrobromic acid. 

Treatment of [RuC1(NH3)5]2+ with Ag(02CCF3), followed by zinc amalgam reduction and addition of amine yields [Ru(L)(NH3)5]2+ (L = cyclohexylamine, benzylamine, methylamine).192 Oxidation of these complexes with Br2 produces the corresponding ruthenium(TII) species [Ru(L)(NH3)5]3+.192 Subsequent oxidation of the amine ligand can readily occur to give imine and nitrile products, explaining the relatively few complexes of this type that have been isolated (see Section 45.4.2). 

Reactions with 3-methylbutanal (82) (for ipsenol, 83) or senecio aldehyde (dimethylacrolein, 84, for ipsdienol, 85) were discussed previously (Vol. 4, p. 467). Many further publications on the subject have s peared. Isoprene can be tribrominated, first with bromine in carbon tetrachloride, then with N-bromosuccinimide. This is one route to 2-bromomethyl-l,3-butadiene (9, R = Br), obtained from the tribromide with zinc amalgam reduction, but in fact the tribromide reacted directly with the aldehydes 82 or 84 to give ipsenol (83) or ipsdienol (85). A reagent used for the reaction of 9 (R = Br) with the aldehydes... 

In connection with our interest in the synthesis of salvianolic acids [22,23], we needed aryllactic acids that are usually obtained by zinc amalgam reduction in boiling hydrochloric acid [39], Serendipitously, we isolated, along with the expected arylllactic acids, 2-hydroxyfuran-2-ones,... 

Ruthenium(II) A range of complexes of the type [Ru(L)(NH3)j] + (e.g. L = pyridine, pyridazine, pyrazine, pyrimidine,triazine, 2-cyanopyridine, 3-cyanopyridine, 4-cyan-opyridine, 2-, 3- and 4-RC(0)-substituted pyridines (R = CHMe2, CH2Et, CHjPr, OMe, NH2, OH, H, Ph ), IV-methylpyrazine, 4,4 -bipyridine, l,2-bis(4 -pyridyl)ethylene," hyp-oxanthine, guanine, xanthine,4-dimethylaminopyridine" ) have been prepared by reaction of [RuCl(NH3)j]Cl2 with a Ag" salt (AgOjCCF3 is often used) followed by zinc amalgam reduction... 

OJ4,im 193 pij195 V-methylpyrazine, 4,4 -bipyridine, l,2-bis(4 -pyridyl)ethylene, hyp-oxanthine, guanine, xanthine,4-dimethylaminopyridine" ) have been prepared by reaction of [RuCl(NH3)5]Cl2 with a Ag " salt (Ag02CCF3 is often used) followed by zinc amalgam reduction... 

This reaction was initially reported by Granacher in 1922. It is the preparation of thionic acid by the treatment of Aldol Condensation product from an aldehyde and rhodanine with a base (e.g., NaOH). Therefore, this reaction is known as the Granacher synthesis or Granacher reaction." The prepared thionic acid in this reaction can be further converted into a variety of derivatives under different conditions. For example, it can be transformed into a-thiol acid under a basic sodium amalgam reduction, whereas aliphatic acid is formed under an acidic zinc amalgam reduction. In addition, when the thionic acid is treated with ammonia, a-keto acid is generated, and the thionic acid can be converted into af-carboxyl oxime in reaction with hydroxylamine, from which either cy-amino acid or aliphatic nitrile forms via the treatment of sodium amalgam reduction or acetic anhydride, respectively. 

Two methods for converting carbonyl groups to methylene units are the Clem mensen reduction (zinc amalgam and con centrated hydrochloric acid) and the Wolff-Kishner reduction (heat with hydra zine and potassium hydroxide in a high boiling alcohol)... 

This, on reduction with zinc dust and acetic acid, yielded the corresponding oxime, which was further reduced by sodium amalgam to -3 4 5-trimethoxyphenylethylamine, CgHjj(OMe)3. CH. CH. NHg, and this proved to be identical with mezcaline (I). Like the latter, it behaves on analysis as if it contained the grouping —NHMe but this had already been disproved by Heffter. Interest in the remarkable physiological properties attributed to mezcaline has led to many syntheses of this alkaloid and of its isomerides and analogues. ... 

Toluene from Toluidine.—It is often desirable to obtain tbe hydiocarbon from the base. The process of diazotisntion offers the only convenient method. The diazonium salt may be reduced by alcohol (Reaction 1, p. 162) or, as in the piesent instance, by sodium stannite. Less direct methods are the con-veision of the diazonium compound into (i) the hydrazine (see p. 174), (2) the acid and distillation with lime (p. 200), (3) the halogen derivative and reduction with sodium amalgam, 01, finally (4) the phenol and distillation with zinc dust. 

Benzoin yields hydrobenzoin on reduction with sodium amalgam, and clesoxybenzoin, C H,CO.CHj.C,Hj, when reduced with zinc and hydrochloric acid. 

Fig. 3. Evans-diagram for the cementation of Cu2+ and Pb2 with zinc amalgam of different zinc content. If the zinc concentration in the mercury employed for this special extraction technique is low, the anodic zinc-dissolution current density may be diffusion controlled and below the limiting cathodic current density for the copper reduction. The resulting mixed potential will lie near the halfwave potential for the reaction Cu2+ + 2e j Cu°(Hg) and only Cu2 ions are cemented into the mercury.

REDUCTION WITH AMALGAMATED ZINC THE JONES REDUCTOR 10.138... 

The most powerful reductant is therefore zinc amalgam, whilst bismuth amalgam is the least reducing. The final reduction products obtained with these amalgams for a few elements are collected in Table 10.10. 

Light filters for colorimeters, see Filters, optical Limiting cathode potential 509 see also Controlled potential electro-analysis Linear regression 145 Lion intoximeter 747 Liquid amalgams applications of, 412 apparatus for reductions, 413 general discussion, 412 reductions with, (T) 413 zinc amalgam, 413 Liquid ion exchangers structure, 204 uses, 204, 560... 

The solutions of mer-OsCl3(PR3)3 undergo an interesting reduction with zinc amalgam [155] to form OsCl2(PR3)2L (Figure 1.62), where L is a molecule abstracted from the atmosphere in the reaction flask if a noble gas, incapable of coordination, is employed, coordinative saturation is obtained by dimerization to [(PR3)3OsCl3Os(PR3)3]+. 

Bajic and Jaselskis [153] described a spectrophotometric method for the determination of nitrate and nitrite in seawater. It included the reduction of nitrate and nitrite to hydroxylamine by the zinc amalgam reactor (Jones reductor) at pH 3.4 and reoxidation of the product with iron (III) in the presence of ferrozine. Interference by high levels of nitrite could be eliminated with azide treatment. Levels of nitrate of 0.1 mg/1 could be detected with a precision of 3% in the presence of large amounts of nitrite and chloride. 

The neutralization values were influenced by reduction with strong reducing agents, lithium aluminum hydride, sodium borohydride, and amalgamated zinc plus hydrochloric acid (35, 46). For the most part, the consumption of NajCOj and of NaOEt decreased in equivalent amounts. This is further confirmation of the assumption that lactones of the fluorescein type or of the lactol type are present. The reaction with sodium ethoxide was shown to be no true neutralization, that is, exchange of H+for Na+, at all, but an addition reaction w ith the formation of the sodium salt of a semi-acetal or ketal ... 

A( ueous solutions of chromium(ll) sulfate have Ijeen prepared from chromium(lll) sulfate by reduction with zinc powder and from potassium dichromate by reduction with amalgamated zinc and sulfuric acid. Solid chromitim(II) sulfate penlahyrlrate can be obtained from the reaction of highly purified chromium metal... 

Another Zinc Reduction. Prepare or activate the zinc as follows 400 g of mossy zinc is treated with 800 ml of 5% aqueous solution of mercuric chloride for 1 hour. Decant the solution off and use the zinc right away. Add. 834 mole of compound to be reduced to the zinc amalgam, followed by as much HCl acid (.834 mole) diluted in as much water as is required to cover all the zinc. Reflux for 6 hours while adding small portions of dilute HCL acid. Cool, separate the upper, wash free of acid (a few portions of dilute sodium hydroxide), dry and distill to get about a 79% yield of product. 

---