Reduction furans

Many other methods for reducing 34 were explored, but none gave more satisfactory results. The best alternative used 1400 psi H2 over Lindlar catalyst under these conditions, furan reduction was suppressed, but reduction of the C(3—4j n bond occurred to some extent, and this byproduct was inseparable from the desired 1 and unreacted 31. 

Palladium catalysts can also be used for furan reductions. Depending on the reaction conditions, civ-substituted tetrahydrofurans (e.g., 8)46, as well as ring-cleaved products, can be obtained. Palladium on barium sulfate or calcium carbonate preferentially gives the tetrahydro-furan derivatives46. 

Ring hydrogenation of furans—Reductive furan ring opening—Preferential hydrogenation of carbon-carbon double bonds s. 16, 86... 

Most known end-of-pipe technologies used for PAHs and dioxin/furan reduction are DeNOx/DeDiox systems " involving the addition of Ugnite coke, activated carbon or an activated carbon/lime mixture (Fig. 5.3). ... 

Hartenstein, H. (2003). Dioxin and Furan Reduction Technologies for Combustion and Industrial Thermal Process Facilities, The Handbook of Environ. Chem., Vol. 3, Part O, pp. 389 23. 

While not as widely used as other methods of generating tetrahydrofurans, furan reductions can be an effective means of generating saturated rings. Outlined here is a single example which represents the state of the art in 2012 [61]. In an effort to... 

In chapter entitled Synthesis of Substituted Tetrahydrofurans, J. D. Rainier outlines the advances that have been made during the last 10 years in the synthesis of tetrahydrofurans such as nucleophilic additions to acetals and hemiacetals, cycloadditions, oxidative cyclizations, furan reductions, Prins-pinacol cascades, ring-opening of bicyclic substrates, and nucleophilic substitutions. 

Hydrogenation with Raney catalysts Ring hydrogenation of furans Reductive furan ring opening Preferential hydrogenation of carbon-carbon doubie bonds... 

The disadvantages associated with the Clemmensen reduction of carbonyl compounds (see 3 above), viz., (a) the production of small amounts of carbinols and unsaturated compounds as by-products, (h) the poor results obtained with many compounds of high molecular weight, (c) the non-appUcability to furan and pyrrole compounds (owing to their sensitivity to acids), and (d) the sensitivity to steric hindrance, are absent in the modified Wolff-Kishner reduction. 

In rats, the oxidative and reductive metaboHsm products have been identified as the 4-hydroxylated furan and [(3-cyano-l-oxopropyl)methyleneamino]-2-4-imidazohdinedione, respectively (27,42). In addition, the ease of electron transfer as a mechanism of activity with nitrofurantoin and nitrofurazone has been studied (43). 

Aminofurans cannot be prepared by reduction of 2-nitrofurans or by hydrolysis of 2-acetamidofurans. The latter are prepared by the reduction of 2-nitrofurans in the presence of acetic anhydride. Benzofuranone (161) and not 2-aminobenzofuran is obtained from tin and hydrochloric acid reduction of 2-nitrobenzo[h]furan (160). 

Pyrrolethiols, readily obtained from the corresponding thiocyanates by reduction or treatment with alkali, rapidly oxidize to the corresponding disulfides. They are converted into thioethers by reaction with alkyl halides in the presence of base. Both furan- and thiophene-thiols exist predominantly as such rather than in tautomeric thione forms. 

The ring closure of 1,4-enediones has also been used for furan synthesis even though the precursor is at the wrong oxidation level. The examples in Scheme 14 indicate some of the ways in which the necessary reduction has been effected. 

Benzo[b]furan, 2-nitro-reduction, 4, 74, 647 Benzo[b]furan, 5-nitro-mass spectrometry, 4, 583 Benzo[b]furan, 2-(4-nitrophenyl)-properties, 4, 708 Benzo[b]furan, 2-phenyl-bromination, 4, 605 chloromethylation, 4, 607 nitration, 4, 604 photochemical reactions, 4, 636 properties, 4, 697 Benzo[b]furan, 3-phenyl-synthesis, 4, 697... 

Benzo[c]furan, 1-cyan 0-3-phenyl-synthesis, 4, 683 Benzo[c]furan, 1,3-diatyl-cycloaddition reactions, 4, 635 reduction, 4, 614 synthesis, 4, 701 Benzo[c]furan, 1,3-di-t-butyl-synthesis, 4, 703 Benzo[c]furan, 1,3-dihydro-NMR, 4, 572-574, structure, 4, 549 synthesis, 4, 683 Benzo[c]furan, 4,7-dihydro-synthesis, 4, 682... 

Furan-2-carbaldehyde, 3-amino-Friedlander synthesis, 4, 648 Furan-2-carbaldehyde, 3-azido-reduction, 4, 647 Furan-2-carbaldehyde, 4-bromo-X-ray diffraction, 4, 543 Furan-2-carbaldehyde, 5-bromo-nucleophilic substitution, 4, 612 reactions... 

Birch reductions in ammonia-tetrahydro-furan-/-butyl alcohol, 49... 

Reductions in ammonia-toluene-tetrahydro-furan solution, 54... 

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