Furan, 3-bromo

The Hiyama coupling offers an alternative when selectivity and/or availability of other reagents are problematic. Hiyama et al. coupled alkyltrifluorosilane 137 with 2-bromo-furan 136 to give the corresponding cross-coupled product 138 in moderate yield in the presence of catalytic Pd(Ph3P)4 and tliree equivalents of TBAF [122, 123]. In this case, more than one equivalent of fluoride ion was needed to form a pentacoordinated silicate. Alkyltrifluorosilane 137 was prepared by hydrosilylation of the corresponding terminal olefin with trichlorosilane followed by fluorination with CuFj. 

A mixture of 2-t-butylfuran and 2,5-di-t-butylfuran is obtained by the action of t-butyl chloride on furan in the presence of mesitylene nolybdenum tricarbonyl." The intermediate in the nitration of furan-2-aldehyde in acetic anhydride has been identified as compound (26). Treatment of 5-bromo-2-furoic acid with sulphur tetrafluoride in hydrogen fluoride yields the dihydrofuran (27). Bromo-furans are converted into aryl-furans by crosscoupling with aryl Grignard reagents in the presence of nickel(II)-phosphine complexes. 2-Furoic acid is lithiated at position 5, 3-furoic acid at C-2. 2-Methylfuran yields the 5-methylthio-derivative by lithiation and subsequent treatment with dimethyl disulphide. The corresponding phenylthio-compound (28) has been converted into a series of 4-substituted 2-methyl-furans (29 R = alkyl, MeaSi, CO2H, or RCHOH) by the sequence bromi-nation, lithiation, treatment with the appropriate electrophile, and, finally, desulphurization with Raney nickel. 2-Lithiofuran reacts with copper(II)... 

Bromo 2-(t-Butoxy)-5-(tri-fl-butylstannyl)furan, PhCH.PdlPPhjl Cl 60 [9J... 

Ben2o[i]furan, cis-5-bromo-2,3-dihydro-3-hydroxy-2-isopropyl-... 

Furan, 3-bromo-C7, 4, 587 <75JCS[Pg.21]

Furan-2-carbaldehyde, 3-bromo- H NMR. 4, 558 (70TL3407) Furan-2-carbaldehyde, 4-bromo-... 

PE, 4, 25, 587 <76JCS(P2)276) Furan-2-carbonitrile, 3-bromo- H NMR, 4, 558 <71BSF990) Furan-2-carbonitrile, 2-hydro-5-methylene- H NMR, 4, 577 75TL36I9, 70TL777) Furan-3-carbonitrile... 

Furan-2-carboxylic acid, 5-bromo-, methyl ester UV, 4, 588 <57JOC323>... 

Benzo[b]furan, 2-aryl-2,3-dihydro- H NMR, 4, 570 Benzo[b]furan, 2-bromo-nitration, 4, 604 Benzo[b]furan, 5-cinnamoyl-properties, 4, 708 Benzo[b]furan, 2-cyano-photochemical reactions, 4, 636 Benzo[b]furan, 2,3-dialkyl-synthesis, 4, 710 Benzo[b]furan, 2,3-dihydro-aromaticity... 

Furan, 2,5-bis(trimethylsilyloxy)-cycloaddition reactions, 4, 625 Diels-Alder reactions, 4, 77 synthesis, 1, 417 Furan, bromo-dipole moments, 4, 553 Furan, 2-bromo-electron diffraction, 4, 537 reactions, 4, 78 synthesis, 4, 604 Furan, 3-bromo-electron diffraction, 4, 537 Furan, 2-bromomethyl-5-nitro-reactions... 

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... 

Furan-2-carbonyl chloride, 5-alkyl-3,4-dichloro-synthesis, 4, 690 Furancarboxamides rotational isomerism, 4, 543 Furan-2-carboxylic acid, 5-acetylamino-ethyl ester reactions, 4, 647 Furan-2-carboxylic acid, amino-properties, 4, 708 Furan-2-carboxylic acid, 5-bromo-nitration, 4, 603, 711 Furan-2-carboxylic acid, 3-methyl-methyl ester bromination, 4, 604 Furan-2-carboxylic acid, 5-methyl-nitration, 4, 602... 

Although bromo derivatives have been used, the two most common ot-halocarbonyl compounds for this reaction are chloroacetaldehyde and chloroacetone. The dicarbonyl component is typically ethyl acetoacetate or one of its derivatives. A variety of bases including triethylamine and potassium hydroxide can promote the reaction however, the most popular base is pyridine. Conversion to the furan takes place either at room temperature or upon heating to 50°C with reaction times varying from four hours to five days and yields ranging from 30-86%. 

The only tetrasubstituted furans that have been prepared using the Feist-Benary reaction are substituted tetrahydrobenzofurans and octahydrodibenzofurans. This strategy was pioneered by Stetter and Chatterjea and applied in a series of total syntheses by Magnus. Stetter demonstrated that 1,3-cyclohexanedione (30) can act as the P-dicarbonyl component and readily combines with either 3-bromo-2-ketobutyric (29) acid or ethyl 2-chloroacetoacetate (32) in the presence of potassium hydroxide to yield tetrahydrobenzofuran derivatives 31 and 33, respectively. ... 

Pyridyne (26) has been shown to exist by trapping it with furan. It must be considered to be an intermediate in the reaction of 3-bromo-2-chloropyridine (49) with lithium amalgam because in the presence of furan a small amount (2%) of quinoline (50) is formed. ... 

Quinolynes are generated and behave analogously to pyridynes. The reaction of 3-bromo-4-chloro- and 3-bromo-2-chloro-quinoline with lithium amalgam in the presence of furan gives phenanthridine (83, 9% yield) and acridine (85, 0.1% yield), respectively, via 3,4-... 

The heteroaryne 1 is trapped as the Diels-Alder adduct when 6-bromo-l,3/4, 5,2,4-trilhia-diazepine is treated with various dienes in the presence of N./V-diisopropylethylamine or sodium methoxide, e.g. trapping of 1 with furan to give 2.391... 

The presence of methyl groups in the 2- and 3-position directs bromination to the adjacent carbon. When both positions are substituted by methyl there is an initial addition process, but the ultimate products are bromi-nated in a side chain. Even 3-methylbenzo[h]furan reacted with NBS to give 2-bromo-3-bromomethylbenzo[h]furan (48HCA78 84BAU445). The 2-phenyl derivative of 1 gave a mixture of 3-bromo and 3,6-dibromo... 

Quaternary ammonium tribromides in methanol-dichloromethane did not brominate the furan ring of 3-methyl-8//-cyclohepta[/>]furan-8-one. Instead, the 7-bromo derivative was formed (92BCJ295). 

Bromination of 4//-furo[3,2-b]indole (50) occurred at the 2-position and was assisted by prior N-benzylation with the 4-benzoyl compound a 61% yield of the 2-bromo derivative was obtained. Thus, a-attack in the furan moiety predominates (78JHC123). When the pyrazolofuran (51) was treated with one molar equivalent of bromine, a mixture of the 2-bromo... 

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