Mesoxalic acid, preparation

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. 

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... 

Mesoxalic acid (or ketomalonic acid) is a good chelating agent and potentially a valuable synthon for organic synthesis. It has been prepared by oxidation of sodium tartronate on PtBi/C catalyst at 60 °C without pH control the maximum yield was 65% at 80% conversion [67]. Operating at 80 °C, 50% mesoxalic acid was obtained at total conversion of tartronic acid. The solution was free from other oxidation products, which were totally oxidized to CO2. 

Quinoxaline-2-carboxylic acids substituted in the 3-position have been widely prepared by reaction of an o-phenylenediamine with mesoxalic acid or its diethyl ester. Mesoxalic acid ester condensation proceeds as shown in Scheme 1. The resulting quinoxalinone carboxylate can be... 

Alloxan was prepared as ossieritrico by Brugnatelli by the action of nitric acid, or of chlorine or iodine in presence of water, on uric acid. Wohler and Liebig called it alloxan because it was supposed to contain the elements of allantoin and oxalic acid. Mesoxalic acid had been noticed by Scheele. Wohler and Liebig investigated a substance prepared by Prout, which they wrongly... 

Diphenylcinnoline can be prepared from benzil monophenylhydrazone in the presence of about 80% sulfuric acid (49MI21200). Synthetically more important, however, is the cyclization of mesoxalyl chloride phenylhydrazones under Frledel-Crafts -conditions (61JCS2828). As outlined in Scheme 67, the starting mesoxalate phenylhydrazones are obtained by coupling dlazotized aromatic amines with diethyl malonate. After conversion... 

DIALKYL MESOXALATES BY OZONOLYSIS OF DIALKYL BENZALMALONATES PREPARATION OF DIMETHYL MESOXALATE (Propanediolc acid, oxo-, dimethyl ester)... 

The volume concludes with the preparation of four useful starting materials. The highly electrophilic tricarbonyl reagent DIMETHYL MESOXALATE finds application as a two-electron component in various pericyclic processes. 9-BROMO-9-PHENYL-FLUORENE is becoming increasingly used for the protection of primary amines, particularly amino acids and amino esters. Two methods for introducing the 9-phenylfluorenyl group are illustrated in the preparations of (S)-N-(9-PHENYLFLUOREN-9-YL)ALANINE AND (S)-DIMETHYL N-(9-PHENYLFLUOREN-9-YL)ASPARTATE. 

Doubts over the orientation of compounds such as those above can frequently be resolved by oxidation of the side chain, decarboxylation of the resulting carboxylic acid, iV-methylation, and comparison with the N-methyl oxo compounds 50 and 51. These compounds have been prepared unambiguously from methylamino aminopyridines by reaction with diethyl mesoxalate (Et02CC0C02Et), " followed by hydrolysis and decarboxylation. Thus 2-amino-3-methylaminopyridine (49) gave the... 

When conventional heating was used, a satisfactory yield was obtained after 4 h at 135 °C in a sealed tube [32]. Ethyl glyoxylate is a weaker carbonyl dienophile than diethyl mesoxalate, and a catalyst (ZnCl2) was added to afford the expected DA adducts with dienes 12 and 13 in goods yields (Table 9.2, entries 2 and 7). For reaction with 13, the catalyst SnCU [34] was substituted by ZnCl2 to prevent formation of the ene reaction product (Table 9.2, entry and 7). Although adduct 16 was previously prepared from 15 [32], its direct DA synthesis from 12 and glyoxylic acid could be performed under the action of MW and without a catalyst (Table 9.2, entry 3). 

Condensation of Hydroxy Aldehydes with Ethyl Glyoxalate or Mesoxalate (I4S). The intermediate 3-keto ester is not isolated. n-Glucoheptoascorbic acid was prepared in this way from glucose. 

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