Furan 2-hydroxymethyl-, reaction

In many cases, substituents linked to a pyrrole, furan or thiophene ring show similar reactivity to those linked to a benzenoid nucleus. This generalization is not true for amino or hydroxyl groups. Hydroxy compounds exist largely, or entirely, in an alternative nonaromatic tautomeric form. Derivatives of this type show little resemblance in their reactions to anilines or phenols. Thienyl- and especially pyrryl- and furyl-methyl halides show enhanced reactivity compared with benzyl halides because the halogen is made more labile by electron release of the type shown below. Hydroxymethyl and aminomethyl groups on heteroaromatic nuclei are activated to nucleophilic attack by a similar effect. 

Timko and Cram were the first to prepare true crown ethers containing the furanyl subcyclic unit ° . Destructive distillation of sucrose yielded 2-hydroxymethyl-5-formyl-furan 7 in 41% yield. This could be reduced to the corresponding diol in 91% yield by treatment with sodium borohydride. Reaction of the diol with tetraethylene glycol dito-sylate, and potassium t-butoxide in THE solution afforded the crown in 36% yield. The approach is illustrated below as Eq. (3.26). 

Some of the typical conditions of polycondensations used for aliphatic and aromatic monomers are not suitable for furan derivatives, e.g., the melt polycondensation of 2,5-furan dicarboxylic acid chloride with 2,5-b/s(hydroxymethyl) furan at about 80 °C only yields a black insoluble product5. The hydrochloric acid liberated in the reaction is clearly responsible for the charring of the furanic diol which like its simpler homologue furfuryl alcohol, resinifies rapidly in acidic media (see below). 

Hydroxymethyl)furan, Triethylamine Jenzen, A. F. et al., J. Fluorine Chem., 1988, 38, 205-208 Reaction of sulfur tetrafluoride with 2-hydroxymethylfuran in presence of triethylamine at —50°C is explosive in absence of a solvent. 

The development of synthetic methods for the selective introduction of short-chain perfluoroalkyl groups into organic molecules is of interest in drug development [464]. Fluoromodifications often confer unique properties on a molecule, for example in terms of increased metabolic stability and lipophilicity and, as a consequence, the pharmacokinetic profiles are often improved [465]. Burger and coworkers developed a domino process consisting of a SN reaction combined with a Claisen and a Cope rearrangement which allows the transformation of simple fluorinated compounds into more complex molecules with fluoro atoms [466]. Treatment of furan 2-917 with 2-hydroxymethyl thiophene (2-918) in the presence... 

An unusual rearrangement of a 3-hydroxymethyl-4-hydroxybutenolide into a furan-3-carboxylic acid occurs in the natural product, photogedunin, when it is treated with alkali the reaction is really related to some of those in sub-sections B, C, and E.llla... 

D-Erythrose has also been exposed to a boiling solution in pH 4.5 buffer. Low yields (<0.2%) of a number of products were obtained, as shown in Scheme 3. These included 5-(hydroxymethyl)-2-furaldehyde (11), 2-acetyl-5-(hydroxymethyl)furan (12), 3,4-dihydroxyacetophenone (13), 3,4-dihydroxy be nzaldehyde (14), 3,4-dihydroxybenzoic acid (15), 2,3-dihydroxytoluene (16), and 1,2-benzenediol (pyrocatechol) (17). Also detected were formic, hydroxyacetic, and 3-hydroxypropanoic acids. Pyrocatechol seems to be a product formed from all carbohydrates boiled in aqueous solutions at pH 4-10 it may constitute a statistical product arising from retro-aldol and re-aldol reactions. It has been shown that the aldol reaction may operate at a pH as low as 4. An aldol reaction... 

Thermolysis of D-fructose in acid solution provides 11 and 2-(2-hydrox-yacetyl)furan (44) as major products. Earlier work had established the presence of 44 in the product mixtures obtained after acid-catalyzed dehydrations of D-glucose and sucrose. Eleven other products were identified in the D-fructose reaction-mixture, including formic acid, acetic acid, 2-furaldehyde, levulinic acid, 2-acetyl-3-hydroxyfuran (isomaltol), and 4-hydroxy-2-(hydroxymethyl)-5-methyl-3(2//)-furanone (59). Acetic acid and formic acid can be formed by an acid-catalyzed decomposition of 2-acetyl-3-hydroxyfuran, whereas levulinic acid is a degradation prod-uct of 11. 2,3-Dihydro-3,5-dihydroxy-6-methyl-4//-pyran-4-one has also been isolated after acid treatment of D-fructose.The pyranone is a dehydration product of the pyranose form of l-deoxy-D-eo f o-2,3-hexodiulose. In aqueous acid seems to be the major reaction product of the pyranone. 

Hydroxymethyl furfural. 2,5-diformylfuran (DFF) is a furan derivative that has many uses, including use as a polymer building block. By utilizing a platinum catalyst supported on carbon, and running the reaction in water at high temperatures, DFF is produced as the major product in neutral solution. If low temperatures and high pH are employed, 2,5-furandicarboxylic acid results. 

The formation of furan derivatives in acid-catalyzed dehydrations of carbohydrate substrates is a well known reaction, first reported by Dobereiner186 in 1832. Among the plethora of compounds formed, 2-furaldehyde is the main product obtained from all of the pentoses, whereas 5-(hydroxymethyl)-2-furaldehyde is the major product... 

Diastereoselective Diels-Alder reactions The (S)- and (R)-3-(2-pyridylsul-finyl)acrylates (1) are obtained by addition of 2-mercaptopyridine to ( + )-menthyl propiolate followed by oxidation and fractional crystallization of the diastereoiso-meric sulfoxides. In the presence of (QH AIG, both undergo highly diastereoselective Diels-Alder reactions with furan to give mainly endo-adducts without epimerization of the sulfoxide group. The products are converted as shown into ( + )- and ( - )-ewdo-2-hydroxymethyl-7-oxabicyclo[2.2.1]heptane (2). 

The transformation of pentoses and hexoses into 2-furaldehyde and 5-(hydroxymethyl)-2-furaldehyde, respectively, by the action of acids is a well-known reaction. Professor Bognar was long interested in ascertaining whether this reaction is reversible. With both a theoretical and a practical goal, the Bogn r group then synthesized the dl forms of several important monosaccharides (xylose, ribose, and arabinose) from the aforementioned furan derivatives. 

Andreu, C. Villarroya, J.-P. Garcia-Gastaldi, A. Medio-Simon, M. Server-Carrio, J. Varea, T. Enzymatic esterification of bicyclic meso-diols derived from 2,5-bis(hydroxymethyl)-furan. An enantioselective Diels-Alder reaction equivalent. Tetrahedron Asymmetry 1998,... 

The most important aspect of the chemistry of the furan ring in 5-hydroxymethylfurfural is its scission under the influence of acidic reagents. In the very earliest work on the acidic degradation of hexoses, levulinic and formic acids were obtained which were shown subsequently to have arisen from the decomposition of 5-hydroxymethylfurfural. This degradation was studied by Teunissen53 87 who measured its rate and showed it to be a unimolecular reaction. He proposed the scheme represented by XLIV-XLIX for the conversion of 5-hydroxymethyl-... 

Pyrrole can be condensed under alkaline conditions with formaldehyde to give products of either N- or C-hydroxymethylation (Scheme 56). Benzo[ ]furan gives an isolable alcohol on reaction with glyoxylate using Y (OTf)3 as catalyst where attack has taken place at C(3) <2000JOC4732>. 

Bis(hydroxymethyl) furan and 5-hydroxymethyl furfural (available from C6 sugars) have been oxidized to furan-2,5-dicarboxylic acid (44)- Linear polyesters, polyurethanes, and polyamides containing these monomers have been described in the literature (45-43) and have been made via condensation polymerization techniques including bulk, solution, and interfacial mixing procedures. Gandini (5,34) reviewed the poly condensation reactions up to 1986 and... 

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