Benzofuran 2- methyl

Benzidine, N,N -diethyl-, 36, 21 Benzidine dihydrochloride, 36, 22 Bcnzil, 34, 42 Benzil dihydrazone, 34, 42 Benzilic acid, 33, 37 2-Benzimidazolethiol, 30, 56 l,2-Benzo-3,4-dihydrocarbazole, 30, 91 Benzofuran, 3-methyl, 33, 43 Benzofurazan oxide, 31,14, 15 37,1 Benzoguanamine, 33,13 Benzoic acid, 32, 94 37, 21 Benzoic acid, -acetyl-, methyl ester, 32, 81... 

Benzofurans, 5-hydroxy-2/3-phenyl-, nitration, 58, 224 Benzofurans, methyl-, side-chain bromination, 59, 249... 

Chromanone, 3-acetamido-2-methyl-reduction, 3, 729 Chromanone, 3-amino-synthesis, 3, 734 Chromanone, 3-arylidene-thermoisomerization, 3, 722 Chromanone, 3-benzylidene-thermolysis, 3, 728 Chromanone, 3-bromo-2-hydroxy-benzofuran from, 3, 729 Chromanone, 6,8-dimethyl-hydroxymethylation, 3, 731 Chromanone, 2,3-epoxy-as synthon, 3, 735... 

Isotubaic acid — see Benzofuran-5-carboxylic acid, 4-hydroxy-2-isopropyl-Isouramil occurrence, 3, 144 5-Isoxalones potentiometry, 6, 11 Isoxanthopterin, 6-acetonyl-structure, 3, 276 Isoxanthopterin, 3,8-dimethyl-rearrangements, 3, 309 Isoxanthopterin, 6-methoxy-3,8-dimethyl-synthesis, 3, 297 Isoxanthopterin, 6-methyl-bromination, 3, 301 Isoxanthopterin, 8-methyl-synthesis, 3, 319 Isoxanthopterin, 6-phenacyl-structure, 3, 276... 

Auwers and others soon discovered that the transformation 3 —> 6 did not consistently give flavonols such as 2. For example, alcoholic alkali treatment of dibromide 11 produced 2-benzoyl-benzofuran-3-one 12 instead of the corresponding flavonol. The same observation was made by Robert Robinson in a failed attempt to make datiscetin in 19257 It has reported that when there is a meta (to the coumarone ring oxygen) substituent such as methyl or methoxy, flavonol formation is hindered, whereas methyl, methoxy, and chlorine substituents at the ortho and para positions are conducive to flavonol formation. ... 

Reaction of the potassium salt of salicylaldehyde with chlo-roacetone affords first the corresponding phenolic ether aldol cyclization of the aldehyde with the ketonic side chain affords the benzofuran (1). Reduction of the carbonyl group by means of the Wolf-Kischner reaction affords 2-ethyl-benzofuran. Friedel-Crafts acylation with anisoyl chloride proceeds on the remaining unsubstituted position on the furan ring (2). The methyl ether is then cleaved by means of pyridine hydrochloride (3). lodina-tion of the phenol is accomplished by means of an alkaline solution of iodine and potassium iodide. There is thus obtained benziodarone (4)... 

Bromomethyl-3,4-dibromo-3,4-dihydrocoumarin 1 (Fig. 11.4) and its chloro-methylated analogue 2b rapidly and progressively inactivate a-chymotrypsin and also the activities of a series of trypsin-like proteases. A benzyl substituent characteristic of good substrates of a-chymotrypsin was introduced at the 3-position to make inhibition more selective. This substituted dihydrocoumarin 3 irreversibly inhibited a-chymotrypsin and other proteases. These functionalized six-membered aromatic lactones, and their five- and seven-membered counterparts, 3//-benzofuran-2-ones 2a26 and 4,5-dihydro-3//-benzo[b]oxepin-2-ones 2c,27 were the first efficient suicide inhibitors of serine proteases. Their postulated mechanism of action is shown in Scheme 11.2. 

From the copper-catalyzed reaction of methyl 2-diazo-3-oxobutyrate 57 a with Z-3-methoxystyrene, dihydrofuran 59 (formed with retention of olefin configuration) and butadienol 60 result130). Such an acyclic by-product also occurs when benzofuran is the cycloaddition partner. In that case, however, regioisomers 61 and 62, arising from the connection of the former diazo carbon with either the 2- or 3-position of the heterocycle, are obtained similarly, two isomeric dihydrofurans 63 and 64 are formed under Cu(hfacac)2 catalysis130). 

The nature of the substituents on the allene can have an impact on the outcome of a [2 + 2] cycloaddition reaction, as was illustrated by the Lewis acid catalyzed cycloadditions of l-thioaryl-3,3-dimethylallene (24) and 1 -methyl- 1-trimethylsilylallene to various 2-alkoxy-p-benzoquinones 25 (e.g. equation 8)17. The reactions were considered to proceed via carbocation intermediates formed by nucleophilic attack of the thioallene on the Lewis acid activated quinone. At lower temperatures, these carbocations closed to cyclobutanes 26, whereas at higher temperatures, the thermodynamically more stable benzofurans 27 were formed. 

The second alcohol toxin of significance is tremetol, the toxin found in white snakeroot in the midwest and ray less goldenrod in the southwest. Tremetol is an oily extract of the plant and was first associated with the toxic effects, and named appropriately by Couch in 1927. Tremetol is a mixture of methyl ketone benzofuran derivatives, including tremetone, dehydrotremetone, and hydroxytremetone (Beier and Norman, 1990). 

Two possible mechanisms are proposed. Primarily the enol radical cation is formed. It either undergoes deprotonation because of its intrinsic acidity, producing an a-carbonyl radical, which is oxidized in a further one-electron oxidation step to an a-carbonyl cation. Cyclization leads to an intermediate cyclo-hexadienyl cation. On the other hand, cyclization of the enol radical cation can be faster than deprotonation, producing a distonic radical cation, which, after proton loss and second one-electron oxidation, leads to the same cyclo-hexadienyl cation intermediate as in the first reaction pathway. After a 1,2-methyl shift and further deprotonation, the benzofuran is obtained. Since the oxidation potentials of the enols are about 0.3-0.5 V higher than those of the corresponding a-carbonyl radicals, the author prefers the first reaction pathway via a-carbonyl cations [112]. Under the same reaction conditions, the oxidation of 2-mesityl-2-phenylethenol 74 does not lead to benzofuran but to oxazole 75 in yields of up to 85 %. The oxazole 75 is generated by nucleophilic attack of acetonitrile on the a-carbonyl cation or the proceeding enol radical cation. 

Substituted acetophenones and a benzofuran were also isolated. The acetophenones may arise in a manner similar to that noted for 2,3-dihy-droxyphenyl methyl ketone (2,3-dihydroxyacetophenone) obtained from D-glucuronic acid. ... 

Reductive detelluration of cyclic telluroethers (typical procedure) To a solution of 2,3-diliydro-2-[(phenylteUuro)methyl]benzofuran (0.338 g, 1 mmol) in toluene (6 ml.) is injected TBTH (0.67 ml, 2.5 mmol) at room temperamre, and the resulting solution is stirred under reflux for 1 h. The solution is evaporated under vacuum and the residual yellowish oil subjected to Si02 column chromatography (eluting with benzene/hexane, 3 1) to give pure 2,3-dihydro-2-methylbenzofuran as a colourless oil (0.128 g (95%) b.p. 93-94°C/23 torr). 

Gaultheria procumbens Unidentified endophyte 5-OH-2-(l -OH- 5-OH-2-(l -0X0-5 methyl-4-hexenyl)benzofuran 67... 

The reaction of 2,5-disubstituted 3-furyl bromides with butyl-lithium and octafluorocyclopentene in dry tetrahydrofuran (THF) at —78°C gave bis(furyl)ethenes 82 (06JMC4690). Photochrome 83 (05JOC10323, 06EJ03105) (29-46% yield) and a series of its derivatives 84 (55-65%) containing different substituents at position 6 of the ben-zofuran ring were synthesized from 3-bromo-2-methyl-1-benzofuran (08JPP(A)146). 

Benzofuran-2-carbaldehydes readily undergo Wittig reactions in tetra-hydrofuran at room temperature with the resonance-stabilized ylide 2-car-boxy-l-methoxycarbonylethyltriphenylphosphorane, affording high yields of ( )-4-(2-benzofuranyl)-3-methoxycarbonylbut-3-enoic acids. This method is preferable to the Stobbe condensation. The Stobbe-type intermediates undergo quantitative cyclization to methyl l-acetoxydibenzofuran-3-carboxylates on exposure to acetic anhydride at 100 C. Examples are shown in Scheme 27. The intermediate 109 has been used in a synthesis of cannabifuran (110), and the intermediate 111 has been used in a synthesis of the lichen metabolite schizopeltic acid (112). ... 

Few data are available on the electrophilic substitution of dibenzofurans containing more than one substituent. 1,4-Dimethyldibenzofuran affords, as expected, the 2-aldehyde on reaction with dichloromethyl methyl ether and tin(IV) chloride. " The nitration of 2,4-dimethyldibenzofuran has also been studied. Acetylation of 4-methoxy-7-nitro- and 8-nitrodibenzofuran occurs exclusively at the 1-position. Similarly, both 4,6- and 3,4-dimethoxydi-benzofuran undergo bromination and acetylation at the 1-position. The acetylation of 1,3-dimethyl-, 1,4-dimethyl-, and 2,4-dimethyl-7-methoxydibenzofuran have been studied the acetyl group enters the 8-position. The chlorination of 3,7-dichlorodibenzofuran has also been studied. ... 

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