Oxalate reductants

EbuUioscopic method, 37 Electrolytic reduction, oxalic acid, 102 nitrobenzene, 144, 145 Eosin, 187 Epichlorhydrin, in Estimation of carbon and hydrogen, 4 halogens, 22 nitrogen, 13 sulphur, 28 Ether, 59... 

Reduction of acid permanganate. Add a few ml. of dil. HgSO to 1 ml. of a solution of oxalic acid or of an oxalate. Warm gently and add a dilute solution of KMn04 drop by drop and note the decolorisation. 

NOTE. Many esters reduce Fehling s solution on warming. This reduction occurs rapidly with the alkyl esters of many aliphatic acids, but scarcely at all with similar esters of aromatic acids (f.g., ethyl oxalate reduces, but ethyl benzoate does not). Note also that this is a property of the ester itself thus both methyl and ethyl oxalate reduce Fehling s solution very rapidly, whereas neither oxalic acid, nor sodium oxalate, nor a mixture of the alcohol and oxalic acid (or sodium oxalate), reduces the solution. 

One route to o-nitrobenzyl ketones is by acylation of carbon nucleophiles by o-nitrophenylacetyl chloride. This reaction has been applied to such nucleophiles as diethyl malonatc[l], methyl acetoacetate[2], Meldrum s acid[3] and enamines[4]. The procedure given below for ethyl indole-2-acetate is a good example of this methodology. Acylation of u-nitrobenzyl anions, as illustrated by the reaction with diethyl oxalate in the classic Reissert procedure for preparing indolc-2-carboxylate esters[5], is another route to o-nitrobenzyl ketones. The o-nitrophenyl enamines generated in the first step of the Leimgruber-Batcho synthesis (see Section 2.1) are also potential substrates for C-acylation[6,7], Deformylation and reduction leads to 2-sub-stituted indoles. 

The reduction of o-nitrophenyl acetic acids or esters leads to cyclization to oxindoles. Several routes to o-nitrophenylacetic acid derivatives arc available, including nitroarylation of carbanions with o-nitroaryl halides[2l,22] or trif-late[23] and acylation of o-nitrotoluenes with diethyl oxalate followed by oxidation of the resulting 3-(u-nitrophenyl)pyruvate[24 26]. 

Acetone, (reduction with) ascorbic acid, citrate, CE, CN , 2,3-dimercaptopropan-I-oI, EDTA, formate, E, 8CN , 80 , tartrate, thiosemicarbazide, thiourea, triethanolamine CE, EDTA, F , 8CN , tartrate, thiourea, triethanolamine Citrate, CN , 8CN , tartrate, thiourea Citrate, EDTA, F , oxalate, tartrate, tiron... 

Mn04 Reduction with arsenate(III), ascorbic acid, azide, hydrazine, hydroxylamine, oxalic... 

In a complexation reaction, a Lewis base donates a pair of electrons to a Lewis acid. In an oxidation-reduction reaction, also known as a redox reaction, electrons are not shared, but are transferred from one reactant to another. As a result of this electron transfer, some of the elements involved in the reaction undergo a change in oxidation state. Those species experiencing an increase in their oxidation state are oxidized, while those experiencing a decrease in their oxidation state are reduced, for example, in the following redox reaction between fe + and oxalic acid, H2C2O4, iron is reduced since its oxidation state changes from -1-3 to +2. 

Re OPe . The final step in the chemical processing of rare earths depends on the intended use of the product. Rare-earth chlorides, usually electrolytically reduced to the metallic form for use in metallurgy, are obtained by crystallisation of aqueous chloride solutions. Rare-earth fluorides, used for electrolytic or metaHothermic reduction, are obtained by precipitation with hydrofluoric acid. Rare-earth oxides are obtained by firing hydroxides, carbonates or oxalates, first precipitated from the aqueous solution, at 900°C. 

Miscellaneous. Chloroplatinic acid is used in the production of automobile catalysts. Platino-type prints based on reduction of Pt(II) to Pt(0) by a photosensitive reducing agent such as iron(III) oxalate are used in art photography (261,262). Infrared imaging devices based on a platinum siLicide detector have been developed (263). 

An early synthesis of pyrido[3,4-6]quinoxalines involved cyclization by strong heating of o-aminoanilinopyridinamine derivatives, e.g. (418) to give (419) (49JCS2540). In a related reaction, o-nitroanilinopyridines (420) were cyclized to pyrido-[2,3-6]- or -[3,4-6]-quinoxa-lines (421) by reduction with iron(II) oxalate, probably via a nitrene intermediate (74JCS(P1)1965). 

From their structures, it appears that the hydrolytic stability of macrocyclic lactones must necessarily be inferior to macrocyclic polyethers. Ease of synthesis of the cyclic esters is therefore one of the aspects which commend them to interest. It is probably for this reason that such lactones have not been made more often by the interesting approach of Kdgel and Schroder . These workers report the ozonolysis of dibenzo-18-crown-6 in a mixture of methanol and dichloromethane at —20°. Reduction of the ozon-ide at —75° using dimethylsulfide followed by warming and addition of acetone led to formation of 6 in 14% yield. The bis-oxalate had mp 164—165° from acetone, very similar to that of the starting crown. The transformation is illustrated below in Eq. (5.9). 

The process is one of electrolytic reduction and the apparatus is similar to that shown in Fig. 77, p. 144. It consists of a small porous cell (8 cm. x 2 cm. diam.) surrounded by a narrow beaher (ii cm. X 6 cm. diam.). The oxalic acid, mixed w lth too c.f. 10 per cent sulphuric acid (titrated against standard baryl.a solution] forms the cathode liquid and is placed in Iht beakei. The porous cell is filled with the same strength of siilphuiic acid and foims the anode liquid. The electrodes ara made from 01 dinary clean sheet lead. The anode consists of i thiu strip projecting about two inches from the cell and tliu... 

On a laboratory scale reduction of KCIO3 with moist oxalic acid generates the gas suitably diluted with oxides of carbon ... 

Dioxides are known for all the actinides as far as Cf. They have the fee fluorite structure (p. 118) in which each metal atom has CN = 8 the most common preparative method is ignition of the appropriate oxalate or hydroxide in air. Exceptions are Cm02 and Cf02, which require O2 rather than air, and Pa02 and UO2, which are obtained by reduction of higher oxides. 

The Reissert procedure involves base-catalyzed condensation of an o-nitrotoluene derivative 1 with an ethyl oxalate (2) which is followed by reductive cyclization to an indole-2-carboxylic acid derivative 4, as illustrated below . ... 

In 1897, Reissert reported the synthesis of a variety of substituted indoles from o-nitrotoluene derivatives. Condensation of o-nitrotoluene (5) with diethyl oxalate (2) in the presense of sodium ethoxide afforded ethyl o-nitrophenylpyruvate (6). After hydrolysis of the ester, the free acid, o-nitrophenylpyruvic acid (7), was reduced with zinc in acetic acid to the intermediate, o-aminophenylpyruvic acid (8), which underwent cyclization with loss of water under the conditions of reduction to furnish the indole-2-carboxylic acid (9). When the indole-2-carboxylic acid (9) was heated above its melting point, carbon dioxide was evolved with concomitant formation of the indole (10). 

The first use of chiral oxazolines as activating groups for nucleophilic additions to arenes was described by Meyers in 1984. " Reaction of naphthyloxazoline 3 with phenyllithium followed by alkylation of the resulting anion with iodomethane afforded dihydronaphthalene 10 in 99% yield as an 83 17 mixture of separable diastereomers. Reductive cleavage of 10 by sequential treatment with methyl fluorosulfonate, NaBKi, and aqueous oxalic acid afforded the corresponding enantiopure aldehyde 11 in 88% yield. 

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... 

One of the syntheses of f1 udalanine begins with base promoted condensation of ethyl fluoroacetate and ethyl oxalate to give This is then converted by hydrolytic processes to the insoluble hydrated lithium salt of fluoropyruvate (58). This last is reductively aminated by reduction with sodium boro-deuteride and the resulting racemate is resolved to give D-flu-dalanine (59). 

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