A Cyclization Approach toward Five-Membered Heteroaromatic o-Quinodimethanes via Fused-3-Sulfolenes

A general strategy involving the zincation of 4-bromo-3-chloro-2-sulfolene, in situ condensation with an α-heterosubstituted acetaldehyde, and subsequent cyclization reaction as the key steps toward the synthesis of furano- and thieno-3-sulfolenes is described. These fused-3-sulfolenes are demonstrated to be good precursors for the corresponding o-quinodimethanes.     

Dialkylative Cyclization Reactions of 3-(Phenylthio)-3-Sulfolenes

3-(Phenylthio)-3-sulfolene (4) underwent bridged dialkylative cyclization with 2-methylene-1,3-diiodopropane to give the bridged bicyclic 3-sulfolene 23, and spirodialkylation with 1,4-diiodobutane and 1,5-diiodopentane to give the spiro bicyclic 3-sulfolenes 15 as the major product. The reaction of 4 with 1,3-diiodopropane led to the fused bicyclic 2-sulfolene 12. 3-(Phenylthio)-3-sulfolenes bearing an ω-iodoalkyl group at the C-2 position gave the fused bicyclic 2-sulfolenes 28 and/or the spiro bicyclic 3-sulfolene 29 depending on the chain length.     

Isomerization of 3-aryl-4-sulfolenes and their reaction with some nucleophilic reagents

Bases convert 3-(4-substituted phenyl)-4-sulfolenes to 3-aryl-3-sulfolenes, which are subsequently isomerized to 3-aryl-2-sulfolenes. The ratios of the products depend on the character of the substituent in the phenyl ring, and electron-acceptor substituents accelerate the isomerization.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1072–1077, August, 1975.     

Reaction of sulfolenes and their derivatives with some sulfur-containing nucleophiles

Reaction of 2-sulfolene, 4-hydroxy-2-sulfolene, 4-bromo- and 3-chloro-2-sulfolenes, 3-chloro-4-hydroxysulfolane, and 3,4-dibromo(dichloro)sulfolanes with sodium methane-, hexane-, allene-, benzene-, and p-toluenesulfinates and magnesium gave 3-methyl-, 3-hexyl-, 3-allyl-, 3-phenyl-, and 3-(p-tolylsulfonyl)sulfolanes, 3-methyl-, 3-phenyl-, and 3-(p-tolylsulfonyl)-4-hydroxysulfolanes, and 3-phenyl- and 4-phenylsulfonyl-2-sulfolenes.     

Cross-coupling of organomanganese derivatives of 3-sulfolenes with allyl and propargyl bromides; a simple synthesis of functionalized 1,3-dienes

Reactions of organomanganese compounds RMnCl (R=3-sulfolen-2-yl or 5-methyl-3-sulfolen-2-yl) with allyl or propargyl bromides afford the corresponding 2-substituted or 2,5-disubstituted 3-sulfolenes in high yields. Thermolysis of the cross-coupling products results in 1,3,6-trienes or l,3-dien-6-ynes.All = allyl.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 106–113, January, 1994.     

Deprotonation/Alkylation Reactions of Sulfolenes

Deprotonation/methylation reactions have been carried out on a series of substituted 2-sulfolenes and 3-sulfolenes. For 2-sulfolenes, both allylic and vinylic deprotonation reactions occur to give, after treatment with methyl iodide, 2-methylated 3-sulfolenes and 2-methylated 2-sulfolenes. These products are useful intermediates because substituted 3-sulfolenes are precursors to substituted butadienes and 2-alkylated 2-sulfolenes are precursors to β-functionalized trans olefins.     

Synthesis of 1-Tosyl-4,6-dihydrothieno[3,4-d]pyrazole 5,5-Dioxides as Precursors to Pyrazole Analogue of o-Quinodimethane

A facile synthesis of 3-substituted 1-tosyl-4,6-dihydrothieno[3,4-d]pyrazole 5,5-dioxides from readily prepared 3-(phenylthio)-4-acyl-3-sulfolenes and their use as precursors to o-dimethylene pyrazole in [4 + 2] cycloaddition are described.     

Type-Two intramolecular diels-alder reactions of pyrazolo-o-quinodimethanes

Two isomeric series of homologous N-(acryloyloxy)alkylated pyrazolo-3-sulfolenes 10a-c and 18a-c have been efficiently synthesized from a common starting material, 4,6-dihydro-1H-thieno[3, 4-c]pyrazole (5). Thermolysis of these fused 3-sulfolenes provides the corresponding o-quinodimethanes which simultaneously undergo "type-two" intramolecular Diels-Alder reactions to form two- and three-atom-bridged tricyclic pyrazoles which are otherwise difficult to prepare. It was also demostrated that, depending on the N-substitution position of the pyrazolo-fused 3-sulfolenes, the temperature required for the thermal extrusion of SO(2) and the regioselectivity of the T2-IMDA reactions were influenced substantially.     

Reaction of 4-arylamino-2-sulfolenes with nucleophilic reagents

The nucleophilic reactions of 4-arylamino-2-sulfolenes with amines, alcohols, and mercaptans give 3-arylamino-2-sulfolenes and 3,4-substituted arylaminosulfolanes, the ratio between which depends on the nature of the reagents and the conditions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1332–1334, October, 1974.     

A Facile Synthesis of 3-Substituted Methyl 4,6-Dihydrothieno[3,4-b]thiophene-2-carboxylate 5,5-Dioxides as Precursors of o-Dimethylene Thiophene

A facile synthesis of 3-substituted methyl 4,6-dihydrothieno[3,4-b]thiophene-carboxylate 5,5-dioxides 1 from 3-(phenylthio)-4-acyl-3-sulfolenes 2 and their use as stable precursors of o-dimethylene thiophene 3 in [4 + 2] cycloaddition are described.     

Reaction of arylamines with some β,β′-substituted sulfolanes and β-substituted 2- and 3-sulfolenes

The reaction of,gb -substituted sulfolanes and-substituted 2- and 3-sulfolenes with aromatic amines was investigated. 4-Arylamino-2-sulfolenes and 3-arylamino-4-hydroxysulfolanes were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1193–1195, September, 1972.     

Ruthenium-catalyzed diyne hydrative cyclization: synthesis of substituted 1,3-diene synthons

[reaction: see text]. A novel and versatile strategy for the synthesis of highly functionalized substituted 3-sulfolenes based on [CpRu(CH3CN)3]PF6-catalyzed hydrative cyclization has been developed. A marked ketone directing effect in ruthenium-catalyzed cyclization was observed for the first time. This provides complementary chemoselectivity for the synthesis of 3-sulfolenes and other cyclic enones. The utility of this method has been demonstrated by SO2 extrusion of 3-sulfolenes to afford 1,3-dienes and the subsequent inter- and intramolecular Diels-Alder reaction.     

Isomerization of 4-amino-2-sulfolenes

The base-catalyzed isomerization of 4-arylamino- and 4-morpholino-2-sulfolenes to 3-substituted 2-sulfolenes was investigated by UV spectroscopy. A shift in the _as frequencies of the SO₂ group was noted in the IR spectra of the latter.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 627–630, May, 1975.     

A General Preparation of 2-Acyl-3-(Phenylthio)-1, 3-Butadienes

The title dienes 1 are prepared by thermolysis of 3-sulfolenes 2, which are readily obtained by ultrasound promoted allylzincation of bromides 4 with aldehydes followed by PCC oxidation.     

Synthesis and Applications of 3-Phenylthio-2-Sulfolenes

Treatment of 3-phenylthio-2-sulfolene ( 1 ) with an equimolar proportion of butyllithium at ?78 °C in THF followed by addition of an electrophile gave the 2-substituted 3-phenylthio-2-sulfolenes (2). The deprotonation was found to proceed only at the vinylic C-2 position. Some of the 2-sulfolenes 2 underwent desulfonylation upon heating with base. Of particular interest was the conversion of 3-phenylthio-2-trimethylsilyl-2-sulfolene ( 2h ) to its 3-sulfolene isomer 6 by sequential addition of butyllithium and salicylic acid at low temperatures. The 3-sulfolene 6 was desulfonylated by Kugelrohr distillation at 150° C under vacuum to give (Z)-2-phenylthio-l-trimethylsilyl-1,3-butadiene ( 8 ). The regiochemistry of the Diels Alder reaction of this highly reactive diene 8 was found to be controlled by the phenylthio group, and the stereochemistry is endo addition. Diene 8 was oxidized to its sulfone derivative 12 which also underwent a stereospecific Diels-Alder reaction.     

Reaction of sulfolanyl sulfonates with some nucleophilic reagents

The corresponding -substituted sulfolane derivatives were isolated in the reaction of 3-sulfolanyl arene(alkane)sulfonates with amines, alcohols, and mercaptans. Depending on the nature of the nucleophile, 3,4-disubstituted sulfolanes and 4- and 3-substituted 2-sulfolenes were obtained with 3,4-sulfolanyl disulfonates and 4-sulfolen-2-yl sulfonates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 625–630, May, 1974.     

Syntheses and Diel-Alder Reactions of Bis(Alkylidene)Cyclohexanes

Substituted cyclohexene-fused 3-sulfolenes have been prepared by the direct deprotonation/alkylation reactions of a readily available starting material. These fused 3-sulfolenes undergo inter- and intramolecular Diels-Alder reactions at high temperatures to give properly substituted bi- and tricyclic molecules.     

The Diels-Alder Reaction of Dienes Derived from Substituted 3-(Phenyl-Thio)-3-Sulfolenes

Substituted 3-(phenylthio)-3-sulfolenes (3) and (4) are good precursors for 2-(phenylthio)-1,3-butadienes (5) and (6). The Diels-Alder reaction of the dienes derived from (3) and (4) with various dienophiles was studied. It was found that heating of sulfolenes (3) with methyl propiolate and N-phenylmaleimide afforded the Diels-Alder adducts of (5) directly and with complete regio- and stereospecificity. The same reaction with methyl vinyl ketone gave a mixture of endo and exo addition products. If sulfolenes (3) were first converted to the dienes (5) using lithium aluminum hydride and then reacted with methyl vinyl ketone in the presence of anhydrous zinc chloride, the stereoselectivity could be improved. Sulfolenes (4) also underwent cycloreversion/cycloaddition with methyl acrylate, methyl vinyl ketone, and N-phenylmaleimide, but gave mostly the double bond-isomerized cycloaddition products. The regiochemistry of cycloaddition was delicately dependent on the dienophiles used.     

The synthesis of oxides of sulfolene and some of its methyl derivatives

The synthesis of the oxides of 3-sulfolene, 2-methyl-3-sulfolene, and 3-methyl-3-sulfolene by the reaction of the corresponding 3-sulfolenes with peracetic acid has been described.     

Synthesis and characterisation of 3- and 4-(pentafluorosulfanyl)benzoic acid derivatives: X-ray structure of 3-SF5-C6H4-COOH

The high yield synthesis of 3- and 4-(pentafluorosulfanyl)benzoic acid derivatives is described starting from the NO₂-derivatives, which are reduced to the corresponding anilines. Then the NH₂- group is converted to bromide and subsequently to the HCO moiety. The benzaldeydes are then oxidised to the corresponding benzoic acids. The X-ray structure of 3-SF₅-C₆H₄-COOH is also reported.