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Aqueous glyoxylic acid

A Friedel-Crafts-type reaction of phenols under basic conditions is also possible. Aqueous alkaline phenol-aldehyde condensation is the reaction for generating phenol-formaldehyde resin.34 The condensation of phenol with glyoxylic acid in alkaline solution by using aqueous glyoxylic acid generates 4-hydroxyphenylacetic acid. The use of tetraalkylammonium hydroxide instead of sodium hydroxide increases the para-selectivity of the condensation.35 Base-catalyzed formation of benzo[b]furano[60]- and -[70]fullerenes occurred via the reaction of C60CI6 with phenol in the presence of aqueous KOH and under nitrogen.36... [Pg.208]

The initial studies of Lubineau et al. [41] focused on reacting cyclopentadiene with aqueous glyoxylic acid at different pH levels. The reaction rate increased substantially at lower pH. At pH 0.9, the reaction of cyclopentadiene in aqueous glyoxylic acid provides a-hydroxy-y-lactones 128 and 129 in 83% yield (73/27 ratio) after stirring the heterogeneous mixture for 1.5 h at 40°C ... [Pg.75]

The hetero Diels-Alder reaction also proceeds with acyclic dienes [45]. For example, reaction of 2-methylpentadiene with aqueous glyoxylic acid furnishes, after 1.5 h at 100°C, a near-quantitative yield of dihydropyrans 133 and 134 in a 64/36 ratio ... [Pg.76]

In a further synthesis, Gut ° used the cyclization of the thiosemi-carbazone of glyoxylic acid (56) the 2-thioxo-5-oxo-2,3,4,6-tetra-hydro-l,2,4-triazine (57) formed was converted to 6-azauracil by applying aqueous solution of chloroacetic acid. (This reaction will be discussed later, e.g.. Section II,B,4,b.) The same procedure was used... [Pg.208]

Bronsted-acid-catalyzed Diels-Alder reactions are not frequent because of the proton sensitivity of many dienes and cycloadducts, especially when long reaction times and high temperatures are required. Examples in aqueous medium involving imines activated by protonation as dienophiles and a proton-promoted Diels-Alder reaction of glyoxylic acid with cyclopentadiene are considered in Section 6.1. [Pg.185]

C-Disaccharide analogs of trehalose were recently [20c] prepared by using as a key step an aqueous Diels-Alder reaction between the sodium salt of glyoxylic acid and the water soluble homochiral glucopyranosil-l,3-pentadiene 19 (Equation 6.1). A mixture of four diastereoisomers in a 41 24 21 14 proportion was obtained after esterification with methanol and acetylation. The main diaster-eoisomer 20 was isolated and characterized as benzoyl-derivative. [Pg.260]

Addition to oxime ethers of glyoxylic acid generates A-benzyloxyamino acids. These reactions have been done in both organic solvents344 and aqueous mixtures.345 The reactions can be done with or without Bu3SnH as a chain carrier. [Pg.974]

Hanessian reported the synthesis of enantiomerically pure or highly enriched allylglycine and its chain-substituted analogs from the reaction of the sultam derivatives of O-benzyl glyoxylic acid oxime with ally he bromides in the presence of zinc powder in aqueous ammonium chloride (Eq. 11.41).72 Brown noticed the critical importance of water in the asymmetric allylboration of /V-trimethylsilyIbcnzaldimines with B-allyldiisopinocampheylborane.73 The reaction required one equivalent of water to proceed (Eq. 11.42). [Pg.355]

The oxidation of aqueous ethanedial to glyoxylic acid is inclined to induction periods and then runaway, cessation and renewed runaway, as the nitric acid is progessively added. Probably this is the same problem as with formic acid, oxalic acid (above). [Pg.1586]

Oxalic acid - Glyoxylic acid Europe, Japan - Pb cathode in aqueous solution... [Pg.145]

The photodecarboxylation of p-(nitrophenyl) glyoxylic acid 156, which was studied by time-resolved and steady-state methods at room temperature93, leads to p-nitrosobenzoic acid and carbon dioxide in good yields with = 0.28 in aqueous solution at pH 2-12 and excitation at 313, 280 or 254 nm (equation 76). An intermediate (Xmax = 350, r 2 xs) observed by nanosecond laser flash photolysis is assigned to the aci-form of the nitroketene... [Pg.783]

Although the present procedure illustrates the formation of the diazoacetic ester without isolation of the intermediate ester of glyoxylic acid />-toluenesulfonylhydrazone, the two geometric isomers of this hydrazone can be isolated if only one molar equivalent of triethylamine is used in the reaction of the acid chloride with the alcohol. The extremely mild conditions required for the further conversion of these hydrazones to the diazo esters should be noted. Other methods for decomposing arylsulfonyl-hydrazones to form diazocarbonyl compounds have included aqueous sodium hydroxide, sodium hydride in dimethoxyethane at 60°, and aluminum oxide in methylene chloride or ethyl acetate." Although the latter method competes in mildness and convenience with the procedure described here, it was found not to be applicable to the preparation of aliphatic diazoesters such as ethyl 2-diazopropionate. Hence the conditions used in the present procedure may offer a useful complement to the last-mentioned method when the appropriate arylsulfonylhydrazone is available. [Pg.14]

Almotriptan has also been synthesized via decarboxylation of the carboxylic acid intermediate 65, but a detailed preparation of 65 was not provided in the patent literature (Scheme 22)." The patent indicates that the carboxy indole 65 was prepared according to the method of Gonzalez.°° Thus, (2-oxo-tetrahydro-3-furanyl)-glyoxylic acid ethyl ester (62) was heated in aqueous H2SO4 to give 2-oxo-5-hydroxypentanoic acid in situ, which was treated with hydrazine 59 to produce hydrazone 63. Fischer cyclization of 63 using HCl gas in DMF gave the lactone 64, which was converted to carboxylic acid 65. Decarboxylation of 65 was catalyzed by cuprous oxide in quinoline at 190 °C to afford almotriptan (5)." ... [Pg.178]

Reduction Products. Glyoxylic acid is produced as aqueous solution by the electrolytic reduction of oxalic acid. It is used for the manufacture of vanillin... [Pg.1185]

Colloidal particles of CdS were examined by Eggins et al. [131]. In C02-saturated aqueous solutions containing tetramethyl ammonium chloride, illumination with an arc-lamp produced formic acid and formaldehyde along with glyoxylic acid and acetic acid. Either hydroquinone or Na2S03 was used as the hole scavenger to increase yields. When CdSe colloids were examined for C02 photoreduction, those with a particle size <50 A were seen to produce formic acid under illumination in aqueous solution, whilst larger particles exhibited no photoreduction [132],... [Pg.310]

A mixture containing 2.83 g (0.01 mole) of 3-hydroxymethyl-9-methyl-2,3,9-tetrahydro-4H-carbazol-4-one-3-glyoxylic acid lactone, 15 ml of dioxane, 1.32 g of triethylamine, 1.0 g of ethanol and 1.64 g (0.02 mole) of 2-methylimidazole is boiled under reflux while stirring for 5 hours. Thereafter, the reaction mixture is diluted with 45 ml of water and cooled down. The precipitate is filtered off, washed with aqueous dioxane and dried to obtain 2.56 g (87.3%) of the title compound, m.p. 220°-223°C. [Pg.2513]

Reductive dechlorination also produces inorganic chloride ion, but glyoxylic acid [Eq. (63)] rather than formic acid. As with the halomethanes, peroxyl radical formation is an important intermediate. Oxygen is clearly important to achieving dechlorination in aqueous solution. [Pg.325]


See other pages where Aqueous glyoxylic acid is mentioned: [Pg.152]    [Pg.346]    [Pg.73]    [Pg.75]    [Pg.77]    [Pg.152]    [Pg.346]    [Pg.73]    [Pg.75]    [Pg.77]    [Pg.27]    [Pg.520]    [Pg.191]    [Pg.221]    [Pg.403]    [Pg.12]    [Pg.353]    [Pg.196]    [Pg.152]    [Pg.22]    [Pg.289]    [Pg.343]    [Pg.134]    [Pg.248]    [Pg.227]    [Pg.3519]    [Pg.25]    [Pg.289]    [Pg.661]    [Pg.22]    [Pg.83]    [Pg.1617]    [Pg.850]   
See also in sourсe #XX -- [ Pg.353 ]




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