2.4- Furan dicarboxylic acid production reactions

Furan-2,5-dicarboxylic acid reacts similarly, but a temperature of 150°C is required for the reactions to proceed. Again, reaction in the presence of disulfur dichloride gives exclusively the fluorinated product, 2,5-difluoro-2,5-bis(trifluoromethyl)-2,5-dihydrofuran (21), while in the presence of chlorine a mixture of chlorofluoro derivatives 22 and 23 is formed.245... 

Aqueous alkali hydrolyzes lactones and the products, e.g. (287), are frequently unstable or recyclize, depending on other substituents present. Coumarin is hydrolyzed by dilute alkali first to the yellow cis acid (coumarinic acid) salt (288) which recyclizes to coumarin on acidification but when heated with alkali isomerizes to the trans acid (coumaric acid) salt (289). When it is desirable to identify the hydrolytic product of such a reaction it is better to incorporate a methylating agent so that the reverse reaction cannot then occur. Hot aqueous alkali converts methyl 3-bromocoumalate (290) into furan-2,4-dicarboxylic acid (73JCS(Pl)ll30). 

The oxidation of substituted furans by hydrogen peroxide is a complex reaction. The products formed include maleic and fumaric acids and saturated dicarboxylic acids.310-312... 

The reaction of furancarboxylic acids with sulfur tetrafluoride leads to the corresponding trifluoromethyl-substituted furans in good yields (see examples in Table 6). A number of furancarboxylic acids, mainly furan-2-carboxylic acids, and furan-2,5- and -3,4-dicarboxylic acids, show a different behavior. Here highly fluorinated dihydrofurans, e g. 25, are formed. This class of compounds is also obtained with the reagent system sulfur tetrafluoride/hydrogen fluoridc/chlorine or sulfur tetrafluoride/hydrogen fluoride/sulfuryl chloride. In some cases chlorine-containing products are found. 

There have been a number of reports on the Maillard reaction. Oxidation of the melanoidins produced from D-glucose and glycine with potassium permanganate and peracetic acid yielded, among other products, furan-2,5-dicarboxylic acid, suggesting that 5-hydroxymethyl-2-furaldehyde is a precursor of the melanoidic pigments produced in the Maillard reaction. 2-(2-Formyl-5-hydroxymethyl-... 

The reverse reactions of Diels-Alder reactions for thermal dissociations of cycloadducts in to dienes and dienophiles at higher temperatures or in the presence of Lewis acid or base are known as the retro-Diels-Alder (rDA) reactions. These reactions in most cases proceed in a concerted process. These reactions are often used for separation of diene or dienophile from their mixture with other compounds. Proper selection of conditions of these reactions provides new dienes and dienophiles, which are important synthons for synthesis of several bioactive natural products and organic molecules of complex structures. For example, the D-A adduct of 4-phenyl oxazole 110 with methyl acetylene dicarboxylate, on retro-D-A reaction gives new compounds, benzonitrile, and furan 3,4-dicarboxylic acid methyl ester 111 [65]. 

Tetrahydrofurandimethanol. THF glycol 2,5-bis(hydroxymethyl)tetrahydrofuran. C,l I tiOy mol wt 132.16. C 54.53%. H 9.15%, O 36.32% Prepd from diallyl by oxidation with perbenzoic acid in chloroform, boiling with di) sulfuric acid and hydrolyzing the reaction product with KOH soln Boeseken, Bee. Trav. Chim. 45, 838 (1926) by Raney nickel reduction of 5 -hydroxymethylfurfural or of dimethyl furan-2.5-dicarboxylate Cope, Baxter, J. Am. Chem. Soc. 77, 393 (1955). The usual form obtained is the cis form, described here. 

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