Furans 2.5- dihydro- from

AHC(18)337>. The 3-alkylbenzo[6 ]furans result from cyclodehydration of aryloxyacetones the most common dehydrating agents are sulfuric acid, phosphorus oxychloride and poly-phosphoric acid. The allyl ethers of phenols can be converted to 2-alkyl-2,3-dihydro-benzo[6]furan by heating with polyphosphoric acid, pyridine hydrochloride or magnesium chloride at 180 °C the intermediate o-allylphenol is not isolated. 

Efforts have been focused on the synthesis of 5-ethyl-5,8-dihydro-8-oxofuro[3,2-Z)][l,8]naph-thyridine 7-carboxylic acid (37), known as DJ-6783, due to its wide spectrum of potent antimicrobial activity <86MI 837-01 >. A few synthetic routes have been studied, which were all based on the strategy of constructing the furan ring from naphthyridine derivatives. A synthetic route demonstrated in... 

Anderson and Horspool have reported on the reaction of some alkyl-2,3-diphenylfurans (131) with tetrachloro-1,2-benzoquinone to give dihydro-furobenzodioxins (132). The subsequent paper describes the synthesis of some phenanthro[9,10-3]furans (133) from the above products (Scheme 3). 

Benzo[b]furan, 2,3-dihydro-2-hydroxymethyl-4//-chromene synthesis from, 3, 764 Benzo[b]furan, 2,3-dihydro-2-isopropenyl-synthesis, 4, 678, 680... 

Benzo[b]furan-4(5H)-one, 6,7-dihydro-synthesis, 4, 710 Benzofuranones H NMR, 4, 579 Benzo[b]furanones from 3-hydroxyflavanone, 3, 729 Benzo[b]furan-2(3H)-ones — see 2-Coumaranones Benzo[b]furan-3(2H)-ones IR spectra, 4, 590 reactions, 4, 650 Benzo[ c]furan-1 (3 W) -ones carbanions, 4, 579 H NMR, 4, 579 reactions with arynes, 1, 415 structure, 4, 552... 

Furan, 2,5-dialkoxy-2-( 1 -hydroxyalkyl)-2,5-dihydro-ring expansion, 1, 425 Furan, 2,5-dialkoxytetrahydro-pyrrole synthesis from, 4, 330 Furan, 2,4-dialkyl-synthesis, 4, 661, 685 Furan, 2,5-dialkyl-... 

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... 

D) Preparation of 2-(1-Hydroxyethyi)-3-Methyi-5-(2-Oxo-2,5-Dihydro-4-Furyi)Benzo[b] Furan (3574 CB) 13,2 grams of compound 3556 CB of which the preparation is described in (C) are treated successively with 66 ml of methylene chloride, 27 ml of methanol and, with stirring, 1.6 grams of sodium borohydride added in stages. The reaciton takes 1 hour. The mixture is poured into water acidified with a sufficient amount of acetic acid, the solvents are stripped under vacuum, the crystalline product removed, washed with water, and recrystallized from ethyl acetate. Yield 90%. MP <=158°C. 

E) Preparation of 2-( 1-Succinyloxyethyl)-3-Methyl-5-(2-Oxo-2,5-Dihydro-4-Furyl)Bemo[b] -Furan (409 CBj 8.65 grams of compound 3574 CB in 43 ml of pyridine are warmed for 30 minutes, on a water bath, with succinic anhydride. At the end of this, the pyridine is stripped off in vacuo. The mixture is treated with dilute sulfuric acid and with ether, the crystalline product filtered off, washed with water and with ether, and recrystallized from ethyl acetate (9.35 grams). MPq = 144°C (measured after drying at 90°C and 0.1 mm). Yield 77%. The product yields an equimolecular compound with morpholine. MPc= 136°C (from ethyl acetate). 

Dihydro-2,5-dimethoxyfuran 824 reacts neat at 24°C with TCS 14 via the intermediate 825, the 2-trimethylsilyloxyfuran 826 (which can also be readily prepared from 5H-furan-2-one), and 827-829 to give the crystalline trimer 830 in 20% yield [21]. In the presence of aldehydes such as thiophen-2-aldehyde 831a or benzaldehyde 831b, however, 824 reacts via 832 to give the condensation products 833 a and 833 b, which are obtained in 30 and 62% yield, respectively [22, 23] (Scheme 6.11). Because it is postulated 2-trimethylsilyloxyfuran 826 is a intermedi-... 

Furan was dimethoxylated to give 2,5-dihydro-2,5-dimethoxyfuran, using electrogenerated bromine molecules generated from bromide salts in electrolyte solutions [71]. This reaction was characterized in classical electrochemical reactors such as pump cells, packed bipolar cells and solid polymer electrolyte cells. In the last type of reactor, no bromide salt or electrolyte was used rather, the furan was oxidized directly at the anode. H owever, high consumption of the order of 5-9 kWh kg (at 8-20 V cell voltage) was needed to reach a current efficiency of 75%. 

Diacyl triafulvenes yield with enamines the 6-amino-5,6-dihydro-6aH-cyclo-penta(b)furans 524 of structure type A/B, type B is only obtained from enamines... 

Scheme 6.76 Generation of l-oxa-2,3-cyclohexadiene (351) from 5-bromo-3,4-dihydro-2H-pyran (376) and trapping products of351 obtained from furan, 2,3-dimethyl-1,3-butadiene, 1,1-diphenyl-ethylene, ( )-l-phenylpropene, ( )-2-butene, (Z)-2-butene and tert-butyl alcohol , according to Schlosserand co-workers.

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