Dichloroacetic acid oxidations

The use of dichloroacetic acid instead of pyridinium trifluoroacetate increases the rate of oxidation considerably. This acid has been used in one case to obtain an optimum yield of the 11-ketoestrone (8) from the corresponding 1 la-hydroxy compound. ... 

The aldehyde 38 was obtained from 35, by way of 36 and 37, by the carbodiimide—dimethyl sulfoxide oxidation procedure52 in the presence of 3-(3-dimethylaminopropyl)-l-ethylcarbodiimide hydrochloride (EDAC)53 and dichloroacetic acid. It was isolated in the form of its crystalline 1,3-diphenylimidazolidine derivative (39) by trapping the freshly prepared aldehyde 38 with N,N -diphen-ylethylenediamine. (This reagent was developed by Wanzlick and Lochel54 for the selective derivatization of aldehydes, and has been exploited for the isolation of nucleoside 5 -aldehydes55 and other aldehydo derivatives of carbohydrates by Moffatt and coworkers.52(b))... 

Both tetrachloroethene and pentachloroethane undergo subsequent hepatic metabolism. Pentachloroethane is reductively dechlorinated by microsomes to yield trichloroethene. (Reductive dechlorination was favored when there were three chlorines on one carbon and at least one chlorine on the vicinal carbon [Thompson et al. 1984], a characteristic shared by hexachloroethane and pentachloroethane). Trichloroethene and tetrachloroethene were then oxidized by hepatic enzymes to form trichloroethanol and trichloroacetic acid as terminal reaction products. Apparently additional dechlorination reactions can occur since labeled dichloroethanol, dichloroacetic acid, monochloroacetic acid, and oxalic acid have been... 

Following oral administration to animals, dichlorvos is rapidly absorbed from the digestive tract and extensively metabolized in the liver. The metabolism of dichlorvos has not been clearly elucidated because almost none of its potential metabolites has been yet unequivocally identified due mainly to its very rapid biotransformation rate (6). It appears, however, that the initial hydrolysis of dichlorvos, which occurs in all species, leads presumably to dichloroacetaldehyde (40), which is further metabolized by reduction to dichloroethanol or oxidation to dichloroacetic acid. In addition, dealkylation to desmethyldichlorvos appears to be another minor route of biotransformation, except in the mouse where desmethyldichlorvos constitutes at least 18% of the administered radioactivity. The metabolites of dichlorvos do not persist in tissues, whereas only trace levels occur in the milk of lactating mammals (41). There is no evidence tliat the metabolites of dichlorvos are toxic. 

A look at the mechanism (page 98) shows that DCC—in order to be attacked by DMSO needs to be activated by protonation. On the other hand, the reaction fails in the presence of a strong acid, such as HC1, H2SO4 or HCIO4, because these would prevent the formation of the sulfur ylide.11 Moffatt et al. found that the oxidation of testosterone (14) succeeds using mild acids with pKa inside a narrow window.14a For example, no oxidation occurs with acetic acid (pKa = 4.76) or trichloroacetic acid (pKa = 0.66), because their pKas lay outside the acidity window, while monochloroacetic acid (pKa = 2.86) leads to a slow and incomplete reaction, and dichloroacetic acid (pKa = 1.25) produces a quantitative oxidation in ten minutes. 

Moffatt et al. found that the optimized reaction conditions developed for the oxidation of testosterone (14), worked ideally in the oxidation of other alcohols. Later, researchers tended to apply, on reactions run at room temperature on very diverse alcohols, these optimized conditions involving 3 equivalents of DCC or other carbodiimide, 0.5 equivalents of pyridinium trifluoroacetate with some extra pyridine added, and neat DMSO or a mixture of DMSO and benzene as solvent. The only substantial changes to this standard protocol involve the growing use of the water-soluble carbodiimide EDC,17 instead of DCC, in order to facilitate the work-ups, and the occasional employment of dichloroacetic acid,18 which proved very effective in the oxidation of some complex polar alcohols, instead of pyridinium trifluoroacetate. 

During the oxidation of greatly hindered alcohols, it can be advisable to use 0.5 equivalents of ortophosphoric acid (MW = 98.0) (solid phosphoric acid) instead of pyridinium trifluoroacetate. This causes an acceleration of the oxidation, although it normally leads to greater amounts of side compounds. On some highly polar compounds, the use of 0.5 equivalents of dichloroacetic acid (DCAA) (MW = 128.9, d = 1.47) can provide best results. 

This fluorine-containing, oxidation-resistant alcohol is best oxidized by the Pfitzner-Moffatt reaction, using dichloroacetic acid as catalyst. Observe the use of toluene, instead of carcinogenic benzene, as solvent. A Swern oxidation was not reproducible, and caused substantial epimerization of the isobutyl side chain. Collins oxidation was successful, but ... 

Metabolism of 1,1-dichloroethane by hepatic microsomes resulted in the production of acetic acid as the major metabolite and 2,2-dichloroethanol, mono-, and dichloroacetic acid as minor metabolites (Table 2-4) (McCall et al. 1983). On the basis of these results, pathways for the metabolism of 1,1-dichloroethane were proposed (Figure 2-3). The initial steps in the metabolism of 1,1-dichloroethane were proposed to involve cytochrome P-450-dependent hydroxylations at either carbon. Hydroxylation at C-1 would result in the production of an unstable alpha-haloalcohol, which can lose HCI to yield acetyl chloride. An alternative, but less favorable reaction, would be a chlorine shift to yield chloroacetyl chloride. These acyl chlorides can react with water to generate free acids or react with cellular constituents. Hydroxylation at C-2 would produce 2,2-dichloroethanol, which would undergo subsequent oxidation to dichloroacetaldehyde and dichloroacetic acid (McCall et al.1983). 

The crystal structure of the hydroxyphosphorane (88) prepared by N2O4 oxidation of (87) showed an almost perfect tbp structure with the unit cell containing two molecules of the same helicity connected by H-bonds between the P-OH and carbonyl groups.The phosphorus ester (89), fashioned from two n-butyl tartrate moieties exists in solution due to intramolecular hydrogen bonds. On treatment with triethylamine, however, it forms the triethylammo-nium salt (90) of the corresponding hydroxyphosphorane. The pKa value of (89) was determined to be 7.7 in DMF and 4.4 in DMSO, similar to values for dichloroacetic acid in the same two solvents. ... 

A great advantage of electrochemical reactions compared with chemical conversions is the effective contribution to pollution control. The direct electron transfer from the electrode to the substrate avoids the problem of separation and waste treatment of the frequently toxic end products of the chemical oxidants or reductants. Furthermore, by electrodialysis, organic acids or bases can be regenerated from their salts without the use of sulfuric acid or sodium hydroxide, for example, which lead to the coproduction of sodium salts or sulfates as waste [79]. At the same time, inorganic acids and bases, necessary for chemical production, are provided by this process. An application of electrodialysis has been demonstrated in the preparation of methoxyacetic acid by oxidation of methoxyethanol at the nickel hydroxide electrode [80]. Finally, unwanted side products can be converted into the wanted product, which increases the economy of the process and reduces the problem of waste separation and treatment. This is accomplished in the manufacture of chloroacetic acid by chlorination of acetic acid. There the side product dichloroacetic acid, formed by overchlorination, is cathodically converted to chloroacetic acid [81]. 

Cuprous Oxide 1317-39-1 Dichloroacetic Acid Methyl Ester 116-54-1 Diisobutyl Adipate 141-04-8... 

An axenic poplar cell culture experiment exhibited conclusively that poplar cells are capable of transforming and mineralizing TCE without the involvement of microbial metabolism. The metabolites of TCE in cell cultures include trichloroethanol, trichloroacetic acid, and dichloroacetic acid, which was the most predominant. Chloral hydrate was also found at levels lower than the detection limit and is a product of TCE oxidation by cytochrome P-450 oxygenase and the precursor of trichloroethanol and trichloroacetic acid in mammalian systems. The same metabolites were identified in field sites where vegetation was exposed to TCE contaminated groundwater and in laboratory studies. ... 

Prepared from chloral and urea by condensation catalysed with HCl, it is a crystalline compound insoluble in water and stable to acids. In alkaline medium it is decomposed into dichloroacetic acid and urea. In the soil it yields trichloroacetic acid by oxidative decomposition. According to Melnikov (1971a) these reactions... 

ETHANE PENTACHLORIDE (76-01-7) CHCljCClj Noncombustible liquid. Incompatible with water, producing dichloroacetic acid. May self-ignite in air. Incompatible with strong oxidizers. Contact with aluminum, cadmium, mercury, hot iron, alkalis, alkali metals causes dehologenation, forming chloroacetylene gas which is spontaneously explosive in air. Contact with potassium may explode (after a short delay) or form shock- and friction sensitive materials. Incompatible with potassium-sodium alloy + bromoform reaction may be violent. 

METHYL DICHLOROETHANOATE (116-54-1) C3H4CI2O2 Combustible, water-reactive liquid (flash point 176°F/80°C). Contact with water causes heat and decomposition to corrosive dichloroacetic acid. Aqueous solution is an acid. Incompatible with sulfuric acid, alkalis, ammonia, aliphatic amines, alkanolamines, alkylene oxides, amides, epichlorohydrin, organic anhydrides, isocyanates, vinyl acetate. Strong oxidizers may cause fire and explosions. Attacks metals in the presence of moisture. Thermal decomposition releases toxic phosgene and HCl gases. 

A Man to in. (2,5-Dioxo-4-imidazolldinyl>urea 5-ureidohydantoin glyoxyldiureide cordianine Psoralon Saptalan. C4H6N40, mol wt 158,12, C 30,38%, H 3.82%, N 35.44%, O 30.36%. Product of purine metabolism. Prepd synthetically by the oxidation of uric acid with alkaline potassium permanganate Org. Syn, coll, vol. II, 23 (1943), By heating urea with dichloroacetic acid C. N. Zellner, 3. R. Stevens, U.S. pat, 2,158,098 (1939 to Merck Co ) Acetyl derivs Biltz. Loewe, J. Prakt. Chem. 141, 291 (1934). Optically active forms have been obtained by extraction procedures. 

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