Zinc amalgam, reduction

The pentammine aqua ion [Ru(NH3)j(H20)]2+, best made by zinc amalgam reduction and aquation of [Ru(NH3)5C1]2+, undergoes extensively studied substitution reactions first order in both the ruthenium complex and the incoming ligand (e.g. NH3, py) and is a convenient source of other... 

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. 

Zinc amalgam reduction of Moiv(TPP)C12 under NO leads to c/s-Mou(TPP)(NO)2 which is converted to trans-Mo (TPP)(NO)(HOMe) on column chromatography (Scheme 13).49... 

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). 

Zinc amalgam reduction of Ru(acac)3 in the presence of olefinic N- or O-donor chelating ligands affords the corresponding complexes 89 of ruthenium(II) . ... 

Zinc amalgam reduction of PhMeAsOjH yields PhMeAsH. Reduction of the arsonic acid function, without attack on the substituted aryl ring, yields p-MeC H jAsH ... 

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... 

Ruthenium(II) [Ru(NH3)50H2] can be most efficiently prepared by zinc amalgam reduction of [RuCl(NH3)5]Cl2 in aqueous solution. More recently, an alternative route avoiding Zn + and Cl" ion has been developed based on the aquation of electrochemically reduced [Ru(03SCF3)(NH3)5] " . Alternative routes include the photolysis and acid-catalysed hydrolysis of [Ru(NH3)g] and the reduction of [Ru(NH3)5(OH2)]. The lability of the aqua ligand in these systems makes [Ru(NH3)jOH2] an excellent starting material for the synthesis of substituted pentaammine complexes, and for the study of their kinetics of formation. 

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. 

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