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2-Vinyl-2,5-dihydrofuran

A facile synthesis of enantiopure tricyclic furyl derivatives employing 4-vinyl-2,3-dihydrofuran via Diels-Alder cycloaddition reaction was reported <02TL7983>. A new capture-ROMP-release procedure for chromatography-free purification of N-hydroxysuccinimide Mitsunobu reactions was reported by Hanson, who used a Mitsunobu reaction to capture a variety of alcohols onto a norbomenyl A-hydroxysuccinirmde monomer. Treatment of this monomer under ROM-polymerization then generated a water-soluble polymer that was readily separable from other by-products. Subsequent reaction with hydrazine was utilized to release the O-alkylhydroxylamines in good purity from the water-soluble polymer <020L1007>. [Pg.176]

The 7, i5-unsaturated alcohol 99 is cyclized to 2-vinyl-5-phenyltetrahydro-furan (100) by exo cyclization in aqueous alcohol[124]. On the other hand, the dihydropyran 101 is formed by endo cyclization from a 7, (5-unsaturated alcohol substituted by two methyl groups at the i5-position. The direction of elimination of /3-hydrogen to give either enol ethers or allylic ethers can be controlled by using DMSO as a solvent and utilized in the synthesis of the tetronomycin precursor 102[125], The oxidation of the optically active 3-alkene-l,2-diol 103 affords the 2,5-dihydrofuran 104 in high ee. It should be noted that /3-OH is eliminated rather than /3-H at the end of the reac-tion[126]. [Pg.35]

The isomerization of vinyl- or ethynyl-oxiranes provides a frequently exploited source of dihydrofurans or furans, but analogous conversions of vinylaziridines have not been applied so often. While most of the examples in Scheme 87 entail cleavage of the carbon-heteroatom bond of the original heterocycle, the last two cases exemplify a growing number of such rearrangements in which initial carbon-carbon bond cleavage occurs. [Pg.137]

Another procedure relies on a domino Michael-O-alkylation reaction sequence to yield a variety of dihydrofurans. Combination of cyclohexanedione (30) with vinyl bromide 50 in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) provides dihydrofuran 51 in 83% yield. Numerous 1,3-dicarbonyls and vinyl bromides are amenable to this methodology, and thus a wide range of products like 51 are available via this strategy. [Pg.165]

Our development of the catalytic enantioselective inverse electron-demand cycloaddition reaction [49], which was followed by related papers by Evans et al. [38, 48], focused in the initial phase on the reaction of mainly / , y-unsaturated a-keto esters 53 with ethyl vinyl ether 46a and 2,3-dihydrofuran 50a (Scheme 4.34). [Pg.179]

In a more recent work the same research group has applied cyclic and acyclic vinyl ethers in the oxazaborolidinone-catalyzed 1,3-dipolar cycloaddition reaction with nitrones [30]. The reaction between nitrone 5 and 2,3-dihydrofuran 6 with 20 mol% of the phenyl glycine-derived catalyst 3c, gave the product 7 in 56% yield as the sole diastereomer, however, with a low ee of 38% (Scheme 6.9). [Pg.219]

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. [Pg.66]

The rhodium-mediated reaction of 69 with 2,3-dihydrofuran (a formal dipolar cycloaddition of a cyclic diazo dicarbonyl compound with a vinyl ether) yields 70. Corrqiound 70 can be transformed in a number of steps to 71 a,b <96TL2391>. [Pg.141]

B- HCCH involving weak primary hydrogen bonds Z- HCCH have revealed large non-linearities, but with an angle 0 that remains reasonably close to those predicted by the rules. Figure 22 illustrates this result through the experimentally determined geometries for the cases when B is 2,5-dihydrofuran [200], oxirane [201], formaldehyde [202], thiirane [203], and vinyl fluoride [204], On the other hand, as noted in Sect. 3.1.3, both... [Pg.67]

Copper(II) triflate has also been used for the carbenoid cyclopropanation reaction of simple olefins like cyclohexene, 2-methylpropene, cis- or rran.y-2-butene and norbomene with vinyldiazomethane 2 26,27). Although the yields were low (20-38 %), this catalyst is far superior to other copper salts and chelates except for copper(II) hexafluoroacetylaeetonate [Cu(hfacac)2], which exhibits similar efficiency. However, highly nucleophilic vinyl ethers, such as dihydropyran and dihydrofuran cannot be cyclopropanated as they rapidly polymerize on contact with Cu(OTf)2. With these substrates, copper(II) trifluoroacetate or copper(II) hexafluoroacetylaeetonate have to be used. The vinylcyclopropanation is stereospecific with cis- and rra s-2-butene. The 7-vinylbicyclo[4.1.0]heptanes formed from cyclohexene are obtained with the same exo/endo ratio in both the Cu(OTf)2 and Cu(hfacac)2 catalyzed reaction. The... [Pg.80]

For some of the reactions depicted in Scheme 14, copper(II) hexafluoroacetyl-acetonate [Cu(hfacac)2] proved to be a better catalyst than other chelates neither cyclopropanes nor allylic insertion products were found, and the yield of dihydrofuran was not affected by temperature in the range 70-132 °C 130). However, in phenylogous vinyl ethers such as 4-methoxystyrene or trans-anethole, cyclopropanes (58a, b) rather than dihydrofurans resulted 131>. [Pg.116]

Considering the above-mentioned facts, according to which simple diazoketones yield dihydrofurans with ketene acetals but cyclopropanes with enol ethers, one exports an interlink between these clear-cut alternatives to exist, i.e. substrates from which both cyclopropanes and dihydrofurans result. In fact, providing an enol ether with a cation-stabilizing substituent in the a-position creates such a situation The Rh2(OAc)4-catalyzed decomposition of -diazoacetophenone in the presence of ethyl vinyl ether produces mainly cyclopropane 82 (R=H), but a small amount of dihydro-... [Pg.122]

Cyclopropane 87, obtained from n-butyl vinyl ether, rearranges to dihydrofuran 88 only at elevated temperature, and also partly during work-up on silica gel113). The complete conversion of 87 into veratrole by the action of HCl/CH3OH gave rise to the analogous two-step synthesis of hydrourushiol monomethyl ether from l-diazo-3,3-dimethoxy-2-nonadecanone 89113). Ether cleavage of the product yields hydrourushiol, one of the vesicant components of, inter alia, poison ivy. [Pg.123]

Ferreira developed a novel method for the preparation of masked 1,4-dicarbonyl derivatives for utilization in the Paal-Knorr synthesis of pyrroles <00SC3215>. In this process, the reaction between diazocompound 3 and n-butyl vinyl ether using dirhodium tetraacetate as catalyst provides dihydrofurans 4 which are easily converted into substituted... [Pg.112]

The Cu(I)-catalyzed cyclization for the formation of ethyl ( )-tetrahydro-4-methylene-2-phenyl-3-(phenylsulfonyl)furan-3-carboxylate 82 has been accomplished starting from propargyl alcohol and ethyl 2-phenylsulfonyl cinnamate. Upon treatment with Pd(0) and phenylvinyl zinc chloride as shown in the following scheme, the methylenetetrahydrofuran 82 can be converted to a 2,3,4-trisubstituted 2,5-dihydrofuran. In this manner, a number of substituents (aryl, vinyl and alkyl) can be introduced to C4 <00EJO1711>. Moderate yields of 2-(a-substituted N-tosyIaminomethyl)-2,5-dihydrofurans can be realized when N-tosylimines are treated with a 4-hydroxy-cis-butenyl arsonium salt or a sulfonium salt in the presence of KOH in acetonitrile. The mechanism is believed to involve a new ylide cyclization process <00T2967>. [Pg.147]

Abstract This chapter presents the latest achievements reported in the asymmetric hydroformylation of olefins. It focuses on rhodium systems containing diphosphites and phosphine-phosphite ligands, because of their significance in the subject. Particular attention is paid to the mechanistic aspects and the characterization of intermediates in the hydroformylation of vinyl arenes because these are the most important breakthroughs in the area. The chapter also presents the application of this catalytic reaction to vinyl acetate, dihydrofurans and unsaturated nitriles because of its industrial relevance. [Pg.44]

Optimum yields of (3-vinyl-y-butyrolactols from the Pd(II) promoted reaction of vinyl triflates with Z-but-2-en-l,4-diol (Scheme 6.33) are attained when tetra-n-butylammonium chloride is added (47]. The lactol is conveniently oxidized to the lactone with celite-supported silver carbonate. The corresponding arylbutyrolactols are obtained in high yield (70-80%) from an analogous reaction of iodoarenes with the enediol. The yields of 2-alkenyl-2,5-dihydrofurans, resulting from the Pd(0) catalysed reaction of cyclic alkynylcarbonates with acrylic esters via tandem C-C and C-0 bond forming reactions, are enhanced by the presence of tetra-n-butyl-ammonium fluoride (e.g. Scheme 6.33) (48]. [Pg.297]

DIHYDROFURAN DIVINYL ETHER METHACROLEIN 2-BUTYNE-1,4-DIOL ganna-BUTYROLACTONE cis-CROTONIC ACID trans-CROTONIC ACID METHACRYLIC ACID METHYL ACRYLATE VINYL ACETATE ACETIC ANHYDRIDE SUCCINIC ACID DIGLYCOLIC ACID MALIC ACID TARTARIC ACID n-BUTYRONITRILE ISOBUTYRONITRILE ACETONE CYANOHYDRIN... [Pg.35]

Stannyl cuprates couple with vinyl halides or triflates [16c-d, 85], and a vinyl stannane produced this way has been used in the synthesis of 7-[( )-alkylidene]-cephalosporins [117]. Vinyl substitution reactions starting from dihydrofurans are... [Pg.107]

Scheme 3.33. Metalate rearrangement of a mixed vinyl(stannyl)cuprate derived from a 2,3-dihydrofuran (TIPS = triisopropylsilyl) [118b]. Scheme 3.33. Metalate rearrangement of a mixed vinyl(stannyl)cuprate derived from a 2,3-dihydrofuran (TIPS = triisopropylsilyl) [118b].
The western part 97 of tylosin aglycon (96), a 16-membered macrolide, has also been synthesized using this Kocienski metalate rearrangement [66]. Treatment of the lithiated dihydrofuran 99 with the stannyl cuprate [67] obtained from Bu3SnLi and CuCN, followed by Mel alkylation, exclusively gave the E vinyl stan-nane 100, in 80% yield. In the last stage, stannyl cupration [68] of the deprotected enyne diol 101 afforded the desired ( , E) stannyl diene 97 in 85% yield. [Pg.307]

Complex [RuCl(=C=C=CPh2)( 7 -p-cymene)(PCy3)][PF6] (or its triflate salt) was also effective in the RCM of enynes. Thus, as shown in Scheme 38, the straightforward synthesis of 3-vinyl-2,5-dihydrofurans 104 from enynes 103... [Pg.195]


See other pages where 2-Vinyl-2,5-dihydrofuran is mentioned: [Pg.113]    [Pg.48]    [Pg.86]    [Pg.45]    [Pg.65]    [Pg.77]    [Pg.77]    [Pg.88]    [Pg.92]    [Pg.133]    [Pg.68]    [Pg.164]    [Pg.187]    [Pg.219]    [Pg.192]    [Pg.192]    [Pg.125]    [Pg.835]    [Pg.157]    [Pg.145]    [Pg.451]    [Pg.223]    [Pg.123]    [Pg.218]    [Pg.199]   
See also in sourсe #XX -- [ Pg.176 ]




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