Benzothiophene-5,5-dioxide

Reductions of five-membered cyclic sulfones with lithium aluminum hydride were run in refluxing ether and of other sulfones in refluxing ethyl butyl ether (92°) (yields 12-92%). Benzothiophene-1,1-dioxide was reduced at the double bond as well, giving 2,3-dihydrobenzothiophene in 79% yield after 18 hours of refluxing in ether [687],... 

Benzothiophene-1,1-dioxide (VI) in benzene solution, is converted in sunlight into a stable photodimer (Vila or VHb), which is considered to contain a central cyclobutane structure.56 196 Even though the monomer cannot be isolated on thermal decomposition of the dimer, the latter in boiling ethyl phthalate decomposes, forming sulfur dioxide and... 

In addition to procedures for pyridine ring closure based on the use of 3-amino-thiophene derivatives, there are alternative methods for the construction of thieno [3,2-Z>]pyridines. One approach made use of cyclic (3-keto sulfones, which proved to be convenient synthons for the modified Hantzsch synthesis of fused pyridines (1986KGS1563, 1990JHC1453, 2000MI1, 2002USP6191140). For example, the reactions of benzothiophene 1,1-dioxide 168 with enamines 169 or methylene-active compounds 170 in the presence of NH4OAc produced fused dihydropyridines 171 (1990JHC1453). 

Benzothiophen-1,1-dioxide is polarographically reducible at about —1.3V at pH > 2 [197]. In alkaline solution the polarographic behavior is complicated by the addition of nucleophiles to the 2,3-double bond. Controlled potential reduction in acetate buffer produced 2,3-dihydrobenzothiophen-1,1-dioxide [198]. 

Michael addition of appropriate nucleophiles to benzo [ ] thiophene 1,1-dioxides followed by intramolecular condensation leads to the formation of heterocycle-annelated benzothiophene 1,1-dioxides. Thus, a wide variety of heterocycle-annelated compounds such as 138-142 were synthesized by addition of nucleophiles to 2-benzoyl-3-chlorobenzo[b] thiophene 1,1-dioxide 121 (Scheme 75) [195,203,204]. 

Photoadditions of bis-(p-sulphonyl)selenide and alkaneselenosulphonates and of thiophenol to alkenes have also been reported. The photoreaction of sulphur dioxide with cis-but-2-ene has been described, and the a-oxygenated benzothiophene dioxides (235) have been prepared in good yield by irradiation of the o-methylbenzaldehydes (236) in the presence of sulphur dioxide as shown in Scheme 14. ... 

A synthesis of (+)-estradiol from an alkyl 1,3-dihydrobenzo[c]thiophene-2,2-dioxide involving o-quinodimethane formation by thermal extrusion of SO2 and subsequent cycloaddition has been achieved in an overall yield of 50% (ref. 143). Thus a chiral cyclopentanone component (ref. 144) was used to alkylate the appropriate benzothiophene dioxide and the required tetracyclic stucture obtained directly with avoidance of the customary hydrogenation. It was found desirable at the alkylation stage to enhance deprotonation at Cl by having a cyano group in the benzenoid ring. The ( anotetracycle (R CN) was reacted... 

R = H) is a potent dienophile/ Unlike open-chain a/3-unsaturated sul-phones, it does not form the corresponding epoxide when treated with hydroperoxide anion, but instead yields the ketone (254) 3-substituted benzothiophen dioxides (253 R = Me, Et, or Ph) give alcohols (255) in this reaction. ... 

Few 1 -benzothiophene-S-oxides 218 were obtained in moderate yields by treatment of 1-arylacetylenes 219 with sulfur dioxide and benzene in the presence of antimony pentafluoride250 (equation 127). A series of cyclic sulphoxides have been prepared by hydrolysis of the corresponding alkoxy sulphonium salts 220251-254 (equation 128). Syn-sulphoxide 221 was obtained in a low yield (15-20%) in the reaction of the dianion of cyclooctatetraene 222 with thionyl chloride255 (equation 129). 

Rhodococcus sp. Strain WU-K2R A Rhodococcus strain capable of sulfur-specific desulfurization of benzothiophene, naphthothiophene (NT), and some of their alkyl derivatives was reported [35]. The metabolites of BT desulfurization were BT sulfone, benzo[c][l,2]oxanthiin S-oxide, benzo[c][l,2]oxanthiin S,S-dioxide, o-hydroxystyrene, 2,(2 -hydroxyphenyl)ethan-l-al, and benzofuran. The NT metabolites were NT sulfone, 2 -hydroxynaphthyl ethene, and naphtho[2,l-b]furan [35], The exact biochemical pathway was not determined, however, part of the pathway for BT desulfurization was speculated to be similar to Paenibacillus All-2. 

Oxidation of thiophene and its derivatives was studied using hydrogen peroxide (H2O2), t-butyl-hydroperoxide and Ti-Beta redox molecular sieve as selective oxidation catalysts. A new reaction pathway was discovered and investigated using C-13 NMR, GC, GC-MS, HPLC, ion chromatography, and XANES. The thiophene oxidized to thiophene-sesquioxide [3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1.8-trioxide] and the sesquioxide oxidized mostly to sulfate. 2-Methyl-thiophene and 2,5 dimethylthiophene also oxidized to sulfate and sulfone products. The Benzothiophene oxidation product was sulfone. This proposed new reaction pathway is different from prior literature, which reported the formation of thiophene 1,1-dioxide (sulfone ) as a stable oxidation product... 

The 4a,9b double bond in 1,2,3,4-tetrahydrodibenzothiophene 5,5-dioxide (68) and similar compounds, is essentially nonaromatic and in this respect resembles the 2,3 bond in benzo[6]thiophene 1,1-dioxide. Catalytic reduction of 68 results in the formation of l,2,3,4,4a,9b-hexahydrodibenzothiophene 5,5-dioxide (92 /o). Subsequent reduction of the sulfone with LAH yields 1,2,3,4,4a,9b-hexahydrodibenzothiophene (69) as an oil (78 /o). Oxidation of 4-keto-l,2,3,4-tetrahydrodi-benzothiophene (44a) to its sulfone with peracetic acid (63 /o) followed by... 

The synthesis and preliminary biological activity of substituted 7-alkylseleno-l,4-dihydro[l,6]naphthyridines have been reported <2000DOC218> along with their further synthetic ttansformations <2001RCB122>. There have also been reports of the preparation of selenium-containing fused heterocycles. The C=0 function in benzothiophen-3-ones, 3,4-dihydrothiopyrano[3,2-. ]benzothiophen-4(2//)-ones, and 3,4-dihydro-2//,5//-thiopyrano[2, 3 4,5]thiopyrano[3,2-/ ]ben-zothiophen-4-ones reacts with selenium dioxide and thionyl chloride to give fused 1,2,3-selena and thiadiazoles via their semicarbazones <1999IJB308>. 

This strategy is used mostly for the synthesis of annelated pyrazoles in which the second reactant has two electrophilic sites in a 1,3-juxtaposition. Under control conditions, the first synthesis of a 3-aminopyrrolo[2,3-d]pyrazole (129) was realized from ethyl(3-cyano-4,5-diphenyl-pyrrolylthio)acetate (128) (Scheme 18) <91T8243>. The synthesis of the benzothieno[3,2-c]pyrazole (131) occurred as a two-step process with initial SNAr addition of hydrazine to the chloro-benzothiophene 5,5-dioxide (130) (Equation (42)) <74LA1248>. 

In the thiophene and benzothiophene series, nucleophilic substitution of hydrogen (Scheme 79) becomes possible due to the ability of 3d-orbitals of the sulfur atom to stabilize negative charge arising in an anionic -complex. Thiophene 1,1-dioxides are very good Michael acceptors. The addition of MeSNa to 3,4-di-// r/-bu ty 1 thiophene 1,1-dioxide <2000CL744> takes place in a 2,5- and 2,3-fashion to give a 56 44 mixture of adducts in 94% yield. 

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