Tetrahydrofuran from furan

Tetrahydrofurans from furans Selective ring hydrogenation... 

Uses. Furfural is primarily a chemical feedstock for a number of monomeric compounds and resins. One route produces furan by decarbonylation. Tetrahydrofuran is derived from furan by hydrogenation. Polytetramethylene ether glycol [25190-06-1] is manufactured from tetrahydrofuran by a ring opening polymeri2ation reaction. Another route (hydrogenation) produces furfuryl alcohol, tetrahydrofurfuryl alcohol, 2-methylfuran, and 2-methyltetrahydrofuran. A variety of proprietary synthetic resins are manufactured from furfural and/or furfuryl alcohol. Other... 

Peroxy acids normally form anhydrides when reacted with 1,2-dicaibonyl compounds in inert solvents or acids in alkaline or acidic media. An exception to this generality is the oxidation of the keto ester (74 Scheme 24), in which the ring oxygen facilitates tetrahydrofuran ring migration. Ohno and coworkers have exploited this reaction to develop a chemicoenzymatic approach from furan to the protected L-ribo-furanoside (75). 

Tetrahydrofurans, preparation, from 1,4-diols, 839 from furans, 833... 

Furans are volatile, fairly stable compounds with pleasant odours. Furan itself is slightly soluble in water. It is readily available, and its commercial importance is mainly due to its role as the precursor of the very widely used solvent tetrahydrofuran (THF). Furan is produced by the gas-phase decarbonylation of furfural (2-formylfuran, furan-2-carboxaldehyde), which in turn is prepared in very large quantities by the action of acids on vegetable residues mainly from the manufacture of porridge oats and cornflakes. Furfural was first prepared in this way as far back as 1831 and its name is derived from furfur which is the latin word for bran in due course, in 1870, the word furan was coined from the same root. 

Moore, J.A. and Kelly, J.E. (1978) Polyesters derived from furan and tetrahydrofuran nuclei. Macromolecules, 11 (3), 568-573. 

The aldehyde group stabilizes the furfural stmcture against the acid-catalyzed fission of the furan ring that readily occurs in furan and alkyl furan derivatives. Basic-type stabilizers, such as tertiary amines, can be used to inhibit oxidation of the furan structure [3]. Furfural can be oxidized to furoic acid or reduced to furfuryl alcohol which can be converted to furan by a catalyzed decarbonylation reaction. On an industrial scale furfural is the source for furfuryl alcohol, tetrahydrofurfuryl alcohol, furan, and tetrahydrofuran. Nitro-furan compounds derived from furfural are used as bactericides in humans. 

Furan is produced from furfural commercially by decarbonylation loss of carbon monoxide from furfural gives furan direcdy. Tetrahydrofuran (3) is the saturated analogue containing no double bonds. 

Therapeutics. Compounds containing the furan or tetrahydrofuran ring are biologically active and are present in a number of pharmaceutical products. Eurfurjdamine [617-89-0] is an intermediate in the diuretic, furosemide. Tetrahydrofurfurylamine [4795-29-3] may also have pharmaceutical applications. 5-(E)imethyiaininomethyi)furfuryi alcohol [15433-79-17 is an intermediate in the preparation of ranitidine, which is used for treating ulcers. 2-Acet5dfuran [1192-62-7] prepared from acetic anhydride and furan is an intermediate in the synthesis of cefuroxime, a penicillin derivative. 2-Euroic acid is prepared by the oxidation of furfural. Both furoic acid [88-14-2] and furoyl chloride [527-69-5] are used as pharmaceutical intermediates. 

In the now-obsolete furfural process, furfural was decarboxylated to furan which was then hydrogenated to tetrahydrofuran (THF). Reaction of THF with hydrogen chloride produced dichlorobutene. Adiponitrile was produced by the reaction of sodium cyanide with the dichlorobutene. The overall yield from furfural to adiponitrile was around 75%. 

Very simple compounds such as alkyl-substituted tetrahydrofurans can be dehydrogenated by chlorosulfonic acid or by oleum, these reagents having some capacity for oxidation, and furylium ions are produced (Section III,B), but the technique has not been exploited synthetically.19 The presence of an easily eliminated group helps indeed, the terpenoid furan solidagenone might well be an artefact formed during isolation from an unstable hydrofuran... 

The course of the reaction of phenacyl bromides (39) with nickel carbonyl is markedly dependent on the solvent employed in tetrahydrofuran the products are 1,2-dibenzoylethanes (cf. 40) but in dimethylformamide, 2,5-diarylfurans (41) are obtained in moderate to excellent yield (Scheme 53).90 It is possible that the furan derivatives (41) arise via intermediate fi,y-epoxyketones which can be isolated as products from a number of a-bromo-ketone substrates [cf. 39 and Section II].28... 

This rearrangement of allylic acetals can also be used for furan annelations, in which the formation of the new tetrahydrofuran ring is coupled with ring enlargement of the starting ring.3 The same dr-fused bicyclic tetrahydrofuran is formed from either one of the cis- or mwr-allylic diols used as starting materials. 

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