Furan opening

Furan opening. Enediones are produced when furans are oxidized with the urea-HjOj adduct catalyzed by MeReOj. 

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... 

Furan hot-box resins are used in both ferrous and nonferrous foundries (66,67). In this process, resin and catalyst are intimately mixed with dry sand and then blown into heated metal boxes containing a cavity the shape of the desired core. In seconds, the surface of the sand mass hardens and, as soon as the core has cured sufficiently to be rigid and handleable the box is opened and the core removed. Automotive cores with exceUent dimensional accuracy and high strengths are made via this forty-year-old process. 

Aqueous ring-opening metathesis polymerization (ROMP) was first described in 1989 (90) and it has been appHed to maleic anhydride (91). Furan [110-00-9] reacts in a Diels-Alder reaction with maleic anhydride to give exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3—dicarboxylate anhydride [6118-51 -0] (24). The condensed product is treated with a soluble mthenium(Ill) [7440-18-8] catalyst in water to give upon acidification the polymer (25). Several apphcations for this new copolymer have been suggested (91). 

The chemical consequences of /3-protonation are illustrated further by the ring-opening reactions of furans with methanolic hydrogen chloride and of (V-substituted pyrroles with hydroxylamine hydrochloride (Scheme 11) (82CC800). 

Benzo[Z)]thiophene reacts with dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate in a cyclo-addition-fragmentation reaction to yield (143), whereas benzo[A]furan and N- methylindole yield products (144) arising from ring opening and recyclization (76AP679). 

Benzo[b]furan, 3-(2-hydroxy-3,5-dichlorophenyl)-5,7-dichloro-properties, 4, 708 Benzo[b]furan, 2-lithio-synthesis, 4, 652 Benzo[i]furan, 3-lithio-ring opening, 4, 79 Benzo[b]furan, methoxy-mass spectrometry, 4, 583 Benzo[b]furan, 6-methoxy-2,3-diphenyl-synthesis, 4, 679... 

With a few recent exceptions the reactions in this group have been with the a-ketocarbenes, CH COOMe, CH COOEt, and CH-COCHs, derived from the corresponding diazo compounds. Sorm and coworkers have reported the ring-opening of furan and methylfurans upon reaction with diazoacetone decomposed by copper, via attack at... 

Furan is typically tiVC) coordinated in a series of organometallic compounds. However, it is its ti (C=C) coordination that opened a perspective toward a broad series of derivatized furans. It can be a bridging ligand forming (C=C)... 

The irradiation of 2-trimethylsilylfuran (29) gave the corresponding ring-opening product 30 in 68% yield (Scheme 12) (83JA6316). Other trimethylsilyl derivatives showed the same behavior (Scheme 12). The allene 32, obtained starting from the furan 31, can be thermally converted into 2,4-ditrimethylsilylfuran (33). 

Treatment of 2-phenyl-l,3-benzoxazepines with hydrochloric acid in acetic acid gives benzo-furans by hydrolytic opening of the oxazepine ring, followed by loss of benzamide and re-cyclization.23... 

Diels-Alder cycloaddition of 3,4-bis(trifluoromethyl)furan with ethyl propynoate involved addition of two a,/3-unsaturated esters followed by acid-catalyzed ring opening, rearrangement, and elimination of ethanol to give a 6,7-bis(trifluoromethyl)isocoumarin-3-carboxylate [92JFC(56)359]. 

The ESR spectrum of the furan radical anion indicates that the Cem-0 bond is ruptured in the electron transfer process whereby the oxygen atom acquires the negative charge and the C-2 end of the open ring possesses a free radical character ... 

A comparison of the cationic polymerization of 2,3-dihydrofurans with that of furan and 2-alkylfurans shows that the complications of the latters two, arising from the dienic character of the monomers, obviously vanish when the monomer is a simple cyclic vinyl ether with just one reactive site, viz. the carbon-carbon double bond. However, it also points out that ring opening in the polymerization of furans by acidic catalysts in the absence of water is unlikely, because otherwise it would also occur to some degree in the polymerization of dihydrofurans. 

This section deals with investigations specifically aimed at producing homopolymers and copolymers of furan carbonyl compounds by the selective opening of the carbonyl bond. The many reports on polymerization of 2-furaldehyde which in fact deal with complicated acid-catalysed resinification reactions which involve both the formyl group and the furan ring are reviewed in Chapter VI. 

The furan derivative (23) has been tested in vivo in tests of motor activity (open-field test) and antinociception (hot-plate test) as well as its capacity to enhance the hypokinetic and/or analgesic actions of subeffective doses of... 

Selective transformations Selective styrene ring opening [103] One-pot domino process for regioselective synthesis of a-carbonyl furans [104] Tandem process for synthesis of quinoxalines [105] Atmospheric oxidation of toluene [106] Cyclohexane oxidation [107] Synthesis of imines from alcohols [108] Synthesis of 2-aminodiphenylamine [109] 9H-Fluorene oxidation [110] Dehydrogenation of ethane in the presence of C02 [111] Decomposition of methane [112] Carbon monoxide oxidation [113]... 

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