Mesoxalic acid

The cyclization of thiosemicarbazones has therefore recently served as the basis for further syntheses of 6-azauracil and 6-azathymine. Barlow and Welch proceeded from thiosemicarbazone of mesoxalic acid (51, 52 R = COOH). The corresponding methylmercapto derivative (53 R = COOH, R = CHs) was hydrolyzed and decarboxylated... 

Dimethoxy-l,2-benzenediamine with mesoxalic acid (HO2CCOCO2H) gave 6,7-dimethoxy-3-oxo-3,4-dihydro-2-quinoxalmecarboxylic acid (213) (0.5M HCl, 98°C, 2 h ... 

Tartronic acid was oxidised to mesoxalic acid on 6%Pt2%Bi/C, prepared by exchange/redox, under acidic conditions (reaction f, Scheme 1) (29% yield at 53% conversion, pH=1.5). Figure 10 shows that the conversion rate of tartronic acid is high at first but decreases as the reaction proceeds, probably because the formed mesoxalic acid is more strongly adsorbed on the surface than tartronic acid. The initial high selectivity tapers off due to over-oxidation. 

This mechanism is supported by the fact that a secondary hydrazone such as (8) yields the azohydrazone (9) rather than the formazan.8 Ketone hydrazones also yield azohydrazones. The coupling of hydrazones of glyoxylic acid (10) with diazonium salts is accompanied by decarboxylation to yield 3-unsubstituted formazans (11). Similarly, hydrazones of mesoxalic acid (12) yield formazans with a carboxyl group in position 3, e.g., 13 (Scheme 2).910 Both 11 and 13 can react with diazonium salts to yield the... 

The ferricyanide oxidation of 4//-thiopyrans 206b to corresponding dioxocyclohexylidene derivatives 423 proceeds in the same manner as in the pyran series.250 Simple 4-thiopyrone (325) and mesoxalic acid were isolated after oxidation of 4-hydroxy-4//-thiopyran (2) with potassium permanganate.4... 

As shown in Scheme 3.4, there are several reaction pathways of glycerol oxidation to form dihydroxyacetone, glyceric acid, hydroxypyruvic acid, mesoxalic acid, and so on. Dihydroxyacetone is formed by the oxidation of a secondary hydroxy group under... 

The uncatalysed Belousov-Zhabotinsky (B-Z) reaction between malonic acid and acid bromate proceeds by two parallel mechanisms. In one reaction channel the first molecular products are glyoxalic acid and carbon dioxide, whereas in the other channel mesoxalic acid is the first molecular intermediate. The initial reaction for both pathways, for which mechanisms have been suggested, showed first-order dependence on malonic acid and bromate ion.166 The dependence of the maximal rate of the oxidation of hemin with acid bromate has the form v = [hemin]0-8 [Br03 ] [H+]12. Bromate radical, Br02, rather than elemental bromine, is said to play the crucial role. A mechanism has been suggested taking into account the bromate chemistry in B-Z reactions and appropriate steps for hemin. Based on the proposed mechanism, model calculations have been carried out. The results of computation agree with the main experimental features of the reaction.167... 

Along with nitration processes, isomerization processes may take place which in turn may lead to various fairly complex reactions. As a result such products as C02, CO, NH3 are formed. Such reactions are particularly notable in the nitration of phenols. Their mechanism has been explained by Seyevetz [81] in the following way. A phenol undergoes nitrosation under the influence of nitrous acid present in the nitrating acid. Nitrosophenol isomerizes to quinone oxime, which oxidizes at the double bonds to form mesoxalic acid and its oxime ... 

Figure 2.2.12 Reaction network of glycerol oxidation (GLY, glycerol DHA, dihydroxyace-tone GLA, glyceric aldehyde GLS, glyceric acid HBT, hydroxypyruvic acid MOS, mesoxalic acid TS, tartronic acid GOX, glyoxal GOS, glycolic acid GYS, glyoxylic acid OS, oxalic acid).

Hypoxanthine 6//-Purin-6-one, 1,7-dihydro- Mesoxalic acid Propanedioic acid, oxo-... 

Mesoxalic acid esters tend to undergo cycloaddition reactions at their central carbonyl function. Treatment of complex 37 with an excess of diethyl mesoxalate furnished the oxadiphosphatricyclo[3.1.0.0 ]hexane 40 as a colorless oil in 17% yield after chromatography (Scheme 15). When a threefold excess of tetracyanoethene was added to a solution of 37 in dichloromethane at —85 °C the color of the reaction mixture changed spontaneously from red to black, and 1,6-diphos-phatricyclo[3.1.0.0 ]hexane 41 was isolated in 15% yield (Scheme 15) <1999S639>. 

Mesoxalic Acid HOOC—C(OH)2—COOH Di— hydroxy Malonic Acid... 

Under such conditions two hydroxyl groups may be linked to this carbon forming a stable compound. Also mesoxalic acid by loss of (CO2) by heat yields glyoxylic acid, as above. 

It should be stated that the evidence is not complete and the constitution of mesoxalic acid is generally accepted as not yet established. 

By the introduction of one more hydroxyl group into malic acid we obtain a di-hydroxy succinic acid which, as a di-hydroxy compound, is analogous to mesoxalic acid and bears the same relation to succinic acid and to malic acid that mesoxalic acid bears to malonic acid and to tartronic acid. The acid of this constitution is the commonly occurring substance tartaric acid.. That tartaric acid contains two carboxyl groups and at the same time two alcohol hydroxyl groups and that it is in fact di-hydroxy succinic acid is proven by several syntheses and reactions. 

Oxidation of Bishy dr azones. Mild oxidation of the bishy drazones (41) with cupric chloride yielded yellow bicyclic compounds (66) and not the anticipated triazoles (72). The structures were confirmed by both degradative and spectroscopic (55-60) methods. Thus, upon treatment with alkali and acidification of the phenyl analogue of 66, the monophenylhydrazide of mesoxalic acid (68) was obtained. This compound gave 69 upon acetylation (57). Acetylation of 66 afforded a mono-O-acetyl derivative whose NMR spectrum showed only one imino... 

These compounds are listed in Table XLVIII. 4-Amino-3,5-pyrazolidinediones have been prepared by reduction of the corresponding 4-oximino compounds.981 1048,1339 The preparation of 4-arylazo-3,5-pyrazolidinediones by direct introduction of this substituent has already been mentioned in Section 2 of this chapter.976,1048 Billow and Bozenhardt257 have prepared 4-phenylazo-3,5-pyrazolidinedione by cyclization of the phenylhydrazone of mesoxalic acid hydrazide in acetic acid (eq. 259). Stepanov and Kuzin1340 have suggested that the... 

Pyrazolidinetrione has been prepared by oxidation of the anilide of mesoxalic acid with hydrogen peroxide in alkaline solution.63... 

The condensation of a-ketoacids and o-phenylenediamines gives quinoxalin-2-ones,7 and mesoxalic acid and o-phenylenediamine undergo the expected condensation reaction to give quinoxalin-3-one-2-carboxylic acid (1). With sodium mesoxalate an anomalous reaction occurs, the initial products (1) and l,2-dihydrobenzimidazole-2,2-dicarboxylic acid (2) undergo an intermolecular hydrogen transfer reaction to yield l,2,3,4-tetrahydro-3-oxoquinoxaline-2-carboxylic acid (3) and benzimidazole-2-carboxylic acid (4).8... 

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