3-Methyl-2-furoic acid, oxidation

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

XXXVI) from this sirup have been unsuccessful. Instead, 2-formyl-5-methyl-3-furoic acid (XLIX) has been obtained. Apparently, oxidation proceeds beyond the stage of glycol cleavage, as with the benzimidazole... 

As an example, a convenient preparation of methyl (E) and (Z)-4,4-dimethoxybutenoa-tes can be performed by anodic oxidation of furfuryl alcohol, furfural or furoic acid via a dimethoxylated dihydrofuran intermediate (Scheme 132) [157]. 

After the autoclaving (100°) of D-glucose solutions, both 5-(hydroxy-methyl)-2-furoic acid and 2,5-furandicarboxylic acid were detected. No attempt was made to remove oxygen from the starting solutions. Although the D-glucose solution was not initially acidic, subsequent experience indicated that the final pH was probably 4. Air exposure (mild oxidation) of the mixtures increased the two furancarboxylic acids at the expense of 11. 

Diloxanide was first prepared by the reaction of 4-hydroxy-A-methyl aniline with sodium cyanide and chloral hydrate in the presence of a base [9]. Furoic acid was prepared by the hypochlorite oxidation of... 

Methyl-2-furoic acid has been prepared by the oxidation of 3-methyl-2-furaldehyde 4 and by the degradation of 3-methyl-2-isovalerylfuran (Elsholtzia ketone).5 3-Methylfuran has been prepared by the present method 6 and more recently by a three-step method starting with methallyl chloride and ethyl orthoformate.7 Circuitous routes from citric acid 8 and malic acid 9 have also been used. 

Although aldehydes are more easily ozidized than alcohols, reagents and conditions are similar in the conversion of both substances to acids. Sulfuric-chromic acid mixture has been used to prepare propionic acid from the alcohol (65%), heptanoic acid from the aldehyde (70%), and furoic acid from furfural (75%). ° Alkaline permanganate is employed in the preparation of methyldiphenylacetic acid from the aldehyde (45%) and ethyl-n-butylacetic acid from the aldehyde or alcohol (74%). ° Acid permanganate is used for the oxidation of heptaldehyde to heptanoic acid (78%) and 6-methyl-l-octanol to 6-methyloctanoic acid (66%). ... 

Further details of Kondo s perillene (236) synthesis (Vol. 5, p. 43 Vol. 6, p. 16) have been publishedanother synthesis was based (Scheme 4) upon photochemical isomerization-lactonization of (237)/ Reduction and alkylation of 3-methyl-2-furoic acid with l-bromo-3-methylbut-2-ene gave (238) which was oxidatively decarboxylated with lead tetra-acetate-cupric acetate to rosefuran (239). ... 

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