Furfural synthesis

Intermediate step in the synthesis of a fragrance from furfural Synthesis of phenylacetic acid, an intermediate in the perfumery industry... 

Furfural is formed by dehydration of pentose. Xylose is a major aldopentose and is involved as a form of xylan in hemicelluloses. Unlike glucose, furfural can be formed from xylose by Bronsted acids alone at high temperature, although the furfural selectivity is low. A variety of Bronsted acid catalysts have been examined for furfural synthesis and they are H-type zeolites such as H-mordenite and H-Y faujasite [183], delaminated zeolite [184], H-MCM-22 [185], ion-exchange resins [186], sulfonated porous silicas [187-189], porous niobium silicate [190], metal oxide nanosheets [51], and sulfated zirconia [191]. Sulfated tin oxide (S04 /Sn02) is an effective catalyst for furfural formation [192] because of the combination of Lewis acid and Bronsted acid properties, as well as HMF synthesis. 

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. 

Sugar is destroyed by pH extremes, and inadequate pH control can cause significant sucrose losses in sugar mills. Sucrose is one of the most acid-labile disaccharides known (27), and its hydrolysis to invert is readily catalyzed by heat and low pH prolonged exposure converts the monosaccharides to hydroxymethyl furfural, which has appHcations for synthesis of glycols, ethers, polymers, and pharmaceuticals (16,30). The molecular mechanism that occurs during acid hydrolysis operates, albeit slowly, as high as pH 8.5 (18). 

Maltol. Otsuka Chemical Co. in Japan has operated several electroorganic processes on a small commercial scale. It has used plate and frame and aimular cells at currents in the range of 4500—6000 A (133). The process for the synthesis of maltol [118-71 -8], a food additive and flavor enhancer, starts from furfural [98-01-1] (see Food additives Flavors and spices). The electrochemical step is the oxidation of a-methylfurfural to give a cycHc acetal. The remaining reaction sequence is acid-catalyzed ring expansion, epoxidation with hydrogen peroxide, and then acid-catalyzed rearrangement to yield maltol, ie ... 

Furfural — see Furan-2-oarbaldehyde, 532 Furfuryl acetate, o -(butoxycarbonyl)-anodic oxidation, 1, 424 Furfuryi acrylate polymerization, 1, 279 Furfuryl alcohol configuration, 4, 544 2-Furfuryl alcohol polyoondensation, 1, 278 reactions, 4, 70-71 Furfuryl alcohol, dihydro-pyran-4-one synthesis from, 3, 815 Furfuryl alcohol, tetrahydro-polymers, 1, 276 rearrangement, 3, 773 Furfuryl chloride reactions... 

Installation of a different side chain completely alters the pharmacological profile leading to a new class of muscle relaxants. The synthesis begins with copper(II)-promoted di-azonium coupling between furfural (j ) and 3,4-dichlorobenzene-diazonium chloride (15) to give bi aryl aldehyde Next, condensation with 1-aminohydantoin produces the muscle relaxant clodanolene (17). ... 

The NMR spectra have shown the formation of Schiff base as an intermediate product in the synthesis of the fully N-deacetylated oligomers from chitosan.32 The mechanism of the Schiff base reaction leading to chain cleavage and formation of 5-hydroxymethyl-2-furfural has been proposed. 

Pure xylan is not employed in industry. but crude xylan or pentosans are of industrial importance. Xylan has been proposed as a textile size but is not employed as yet for this purpose.130 Perhaps the largest use of pentosans is in their conversion to furfural, which has many applications and serves as the source of other furan derivatives. At the present time, large quantities of furfural are used in the extractive purification of petroleum products, and recently a large plant has been constructed to convert furfural by a series of reactions to adipic acid and hexamethylene-diamine, basic ingredients in the synthesis of nylon. In commercial furfural manufacture, rough ground corn cobs are subjected to steam distillation in the presence of hydrochloric acid. As mentioned above, direct preferential hydrolysis of the pentosan in cobs or other pentosan-bearing products could be used for the commercial manufacture of D-xylose. 

The two most important natural pentoses, 1 -arabinose and 1 -xylose, occur in nature as polymeric anhydrides, the so-called pentosans, viz. araban, the chief constituent of many vegetable gums (cherry gum, gum arabic, bran gum), and xylan, in wood. From these pentapolyoses there are produced by hydrolysis first the simple pentoses which are then converted by sufficiently strong acids into furfural. This aldehyde is thus also produced as a by-product in the saccharification of wood (cellulose) by dilute acids. Furfural, being a tertiary aldehyde, is very similar to benzaldehyde, and like the latter undergoes the acyloin reaction (furoin) and takes part in the Perkin synthesis. It also resembles benzaldehyde in its reaction with ammonia (p. 215). 

C4-C5 bond formation and between C9 and CIO. In both cases, the addition of silyl enol ether 2 to furfural was achieved with the T0I-BINAP-CUF2. For the synthesis of the C1-C7 segment the S-catalyst was used and the J -catalyst furnished segment 27 (Scheme 11). 

Recent work on the synthesis, structure and some properties of macromolecules bearing furan rings is discussed. Two basic sources of monomers are considered, viz. furfural for monomers apt to undergo chain polymerization and hydroxymethylfurfural for monomers suitable for step polymerization.Within the first context, free radical, catiomc and anionic systems are reviewed and the peculiarities arising from the presence of furan moieties in the monomer and/or the polymer examined in detail. As for the second context, the polymers considered are polyesters, polyethers, polyamides and polyurethanes. Finally, the chemical modification of aU these oligomers, polymers and copolymers is envisaged on the basis of the unique reactivity of the furan heterocycle. 

A number of lower volume chemicals can be obtained from wood hydrolysis. Furfural is formed from the hydrolysis of some polysaccharides to pentoses, followed by dehydration. This process is still used in the Soviet Union. Furfural is used in small amounts in some phenol plastics it is a small minor pesticide and an important commercial solvent. It can be converted into the common solvent tetrahydrofuran (THF) and an important solvent and intermediate in organic synthesis, furfuryl alcohol. 

In the Claisen-Schmidt condensation at the same temperature and with ethanol solvent present, lower yields of a-enones were observed. The best yield corresponds to condensation of the most reactive furfural with acetophenone, giving 95% a-enone after 1 h in a batch reactor. A comparison of the results characterizing the two reactions led to the conclusion that the W-H reaction provides the more efficient and selective synthesis of a-enones however, the CS condensation provides the more economic approach. 

Ciclopirox olamine (Loprox) is a pyridone derivative available for the treatment of cutaneous dermatophyte infections, cutaneous C. albicans infections, and tinea versicolor caused by Malassezia furfur. It interferes with fungal growth by inhibiting macromolecule synthesis. 

A new commercial use for butadiene is its employment in the nylon synthesis joining furfural, benzene, and cyclohexane as raw materials for nylon salt components. Amother olefinic hydrocarbon, which has found large scale application in recent years, is propylene tetramer, widely employed in reaction with aromatic nuclei to yield an alkylated aromatic base used in synthetic detergent production. 

A simple synthesis of the novel hydroxylase inhibitor oudenone (76) has been reported which utilizes the furan ring as a masked hydroxybutyl unit (71JA1285). 2-Acetyl-l,3-cyclopentanedione was condensed with furfural in the presence of morpholine to yield (75). Hydrogenation of this product over platinum in the presence of sodium hydroxide followed by neutralization with hydrochloric acid yielded ( )-oudenone plus the side product (77 Scheme 18). It is interesting to note that hydrolysis of (76) at 150 °C in a sealed tube splits it into 1,3-cyclopentanedione and y-propyl-y-butyrolactone, a reaction which is the reversal of the foregoing synthetic process. 

The preceding sections described the newer methods for the synthesis of furan and its derivatives. This section snmmariy.es the best practical methods for the synthesis of the parent furan and benzofuran ring structures and their substituted derivatives. It is from furfural that furan itself is prepared industrially by the catalytic decarbonylation in steam. 

Acetyl furan [1192-62-7], prepared from acetic anhydride and furan is an intermediate in the synthesis of cefuroxime, a penicillin derivative. 2-Furoic 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. 

Buten-1-ol, 2-chloro-, acetate, 67,105 2-Butenol, 4-(diethylamino)-, acetate, 67, 105 Butenolide synthesis, from furfural, 68, 162... 

At that time, however, these reactions were not brought to the level of preparative synthesis of nitriles. The main obstacle seemed to be further transformation of the nitriles to acids. In some cases, upon treating al-doximes with alkalies, it was not at all possible to fix nitriles since they immediately converted to acids. The anti(E)-isomers exhibit an enhanced reactivity in these cases. Thus, when boiled in 2 N NaOH, -aldoximes are slowly converted to a mixture of the corresponding carboxylic acids and sy/i(Z)-aldoximes to evolve ammonia (36JA1227). Under these conditions for 4 hr the - and Z-benzaldoximes undergo 13 and 48% conversion to form benzoic acid in 10 and 38% yield, respectively. Analogously, the -and Z-oximes of furfural, under the same conditions for 1.5 hr, are converted to furan-2-carboxylic acid in 33 and 62% conversion and 18 and 49% yield, respectively. 

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