Furans, sulfonyl

R, 3 R, 4 R )-2-hutyltetr(ihydm-3-methyl-4-(pheny sulfonyl)furan yield 89% 95% ds... 

While (Z)-l,2-bis(phenylsulfonyl)ethylene (140) does not add to dienes such as furan, cyclopentadiene, cyclo-octatetraene, indene and /f-naphthol, ( )-l,2-bis(phenylsulfonyl)ethylene (141) is more reactive and the reaction with furan proceeds at room temperature for 2 h to give the adduct in 95% yield. The reactivity of dienophiles having sulfonyl group in the [4 + 2]cycloaddition is shown in equation 10393,101. 

AryT3,4-fused furans 63 are synthesized in moderate to good yields from propargyl nucleophiles and a-sulfonyl a,p-unsaturated ketones under palladium catalysis conditions... 

Tolylsulfones of indoles, pyrroles, pyrazoles, furans, thiophenes, indolines, and dibenzofurans react with tributyltin hydride under radical conditions by t/wo-substitution. The most likely mechanism appears to be addition of the RjSiv radical to the ring, followed by elimination of the sulfonyl group, but an electron-transfer mechanism cannot be excluded (Equation (61)).199... 

The reaction of alkynyllithium compounds with alkoxycarbene tungsten complexes leads to anionic propargyl tungsten complexes (Figure 2.33 see also Figure 3.9). These intermediates are stable at low temperatures and react upon Lewis acid catalysis with aldehydes or A -sulfonyl imines to yield five-membered heterocycles [280]. Oxidative methoxycarbonylation [375] of the intermediate vinyl tungsten complex, followed by elimination of methanol leads to pyrroles or furanes (Figure 2.33 Entry 6, Table 2.22). 

The Diels-Alder reaction between l,3-diarylbenzo[c]furans and simple alkenes and alkynes has been much investigated kinetically. Glass and Smith found a remarkable enhancement of dienophilicity by the trifluoromethane sulfonyl group in a series of substituted phenylacetylenes of type 205 with 205 (R = SiMcj) no reaction occurred. 

A number of patents have appeared on the preparation of biologically active sulfonyl derivatives of 2,3-dihydro-l,2,3-diazaborines. The boron heterocycle is fused to benzene, furan, pyrrole or thiophene e.g. 79GEP2809212). Apparently the compounds have bactericidal as well as fungicidal and trichomonacidal properties. 

An intramolecular 2-alkylation was also observed in a sulfonyl free radical induced addition-cyclization <95SL763>. A key intermediate in a new synthesis of pallescensin A (a biologically active labdane diterpene) was prepared by a cationic cyclization reaction with a furan <95SYN1141>. The sonochemical Barbier reaction was extended to carboxylate salts. 2-Furanylketones 10 can be obtained by sonication of a mixture of furan, lithium carboxylate, an alkylchloride, and lithium in THF <95JOC8>. 

Figure 8 Turnover of DFB to DFH in microsomes prepared from cell lines expressing a single CYP. Abbreviations DFB, [3-[(3,4-difluorobenzyl)oxy]-5,5-dimethyl-4-[4-(methyl-sulfonyl)phenyl]furan-2(5//)-one] DFH, [3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl) phenyl] furan-2(5//)-one] CYP, cytochrome P450. Source From Ref. 32.

In the tetrahydrofuran compounds there is opportunity for the existence of cis and irans isomers. They have been separated81 in the case of XL and XLII, the cis-form of which forms an anhydride. Evidence for the existence of the cts-form of 2,5-dishydroxymethyltetra-hydrofuran (XXXVIII) is found in the behavior of either its dichloro-or di-toluene-p-sulfonyl derivative with methanolic ammonia. From this reaction the dicyclic compound, 8-oxa-3-aza6fcyeZo [3,2,1] octane (XLIII) is obtained which can have been formed only from the m-form of the dicarbinol.82 An example of the addition of bromine to the furan... 

Nucleophilic substitution is a relatively rare reaction with pyrrole, thiophene, or furan and requires an activating group such as nitro, carbonyl, or sulfonyl, just as it does with benzene (Chapter 23). Here is an intramolecular example used to make the painkiller ketorolac. 

Furan (and 2,3-dihydrofuran) reacted as a 2jt-component with 4-vinylidene-2-oxazolidinone in a formal inverse electron demand Diels-Alder reaction with concomitant 1,3-sulfonyl migration to furnish a tricyclic product, as depicted below <07CEJ9686>. 

SULFONYL)M ETHYL] FUR AN AND 2-METHYL-3-[(PHENYLSULFONYL)METHYL]-2-CYCLOPENTEN-1-ONE (Benzene, [(2,3-dlbromO 1-propenyl)sulfonyl]>, Furan, 2-methyl-4-[(phenylsulfonyl)methyl]-, and 2-Cyclopenten-l-one,... 

The isomeric Step 4 ester, 5-(4-fluorophenyl)-4-(4-(methylthio)-phenyl)thiophene-2-carboxylic acid methyl ester, (I), has been prepared (3). The Step 5 furan derivative, (II), 3-(4-fluorophenyl)-4-(4-(methyl-sulfonyl)phenyl)furan has also been prepared and is described (3). 

Cesium fluoride promoted oxirane preparation starting from bis(sulfonyl fluorides) has been reported. In general, epoxide formation predominates over furan synthesis. Investigations of cyclohexane derivatives 1 show trans elimination to form 2 this still holds true when the syn chlorine is substituted by a bromine.Epoxide 4 is a versatile, general, enan-liomerically pure building block that is best synthesized by substitution of the mesylate 3. ... 

One additional example of a reaction of an enol-type derivative with an in situ-produced N-sulfonyl iminium species involves the TiCl4-pro-moted reaction of 22 with acetoxy furan 86 to yield butenolide 87 [25b] [Eq. (23)]. 

The influence of the organic moiety of the azide in cylcoadditions to enol ethers is analogous to that in additions to enamines. Comparative cycloadditions of 4-(methoxyphenyl)-, 4-(nitrophenyl)-, and 4-toluene-sulfonyl azide to 2,3-dihydro-furan show that the rate of cycloaddition increases dramatically in the sequence mentioned (Huisgen et al., 1965). Yet, the dihydrotriazoles formed (2.174) are stable only in the case of the first aryl azide mentioned. With 4-toluenesulfonyl azide the product of dediazoniation (2.175) was the only compound detected (96% yield). Analogous results were obtained with 3,4-dihydro-2//-pyran. 

Similar to furan, thiophene can be perfluoroalkylated in position 2 by the radicals, generated from perfluoroalkane sulfonyl chloride by ruthenium (11) catalyst. ... 

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