Thiophene-5-oxides

Thiophene oxides and dioxides have recently been thoroughly reviewed280,281. 

The cycloaddition reactions of thiophene oxides and dioxides (290 and 291280,281) have already been discussed (Section V.A). 

Thiolane oxides, Thiolene oxides, Thiophene oxides... 

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... 

Oxidation of these model sulfur compounds was studied without solvent to investigate the chemical structure of the products using S K-edge XANES. A solvent free tri-phase (organic/ H202aq./catalyst) was used under the described conditions. Figure 1 shows the XANES spectra from the organic and aqueous phases as well as reference materials. The thiophene oxidized to thiophene-sesquioxide [3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1.8-trioxide ] first.. The sesquioxide solid precipitated from the solvent free reaction mixture and was identified by NMR, IR and C,H,S elemental analytical. The sesquioxide oxidized to sulfate. 2-MT and 2,5 DMT also oxidized to... 

The oxidation of thiophene and its derivatives with H202 was studied using a Ti-Beta molecular sieve. The oxidation product is very dependent from the aromaticity of model compounds. The thiophene oxidation product was mostly sulfates and the benzothiophene oxidation product was benzothiophene sulfone. Oxidation of mono and di-alkyl thiophenes also produced sulfates and sulfones. The diffusivity and aromaticity of the relevant sulfur compounds, intermediates and stable product, as well as the proposed new mechanism of oxidation will be discussed. This proposed new reaction pathway is different from current literature, which reports the formation of sulfones as a stable oxidation product. 

The observed catalytic effect of the crown ether appears to be dependent on the nucleophile employed in both polymerization and corresponding model reactions. Not surprisingly, it appears that the stronger the nucleophile employed, the smaller the catalytic influence of the crown ether. For example, with potassium thiophen-oxide yields of polymer or model products were almost quantitative with or without catalyst. By contrast, the reaction of PFB with potassium phthalimide, a considerably weaker nucleophile, affords 6 in 50% with catalyst and in 2-3% without catalyst under identical conditions. However, it may be that this qualitative difference in rates is, in fact, an artifact of different solubilities of the crown complexed nucleophiles in the organic liquid phase. A careful kinetic study of nucleophilicity in catalyzed versus non-catalyzed reactions study is presently underway. 

This paved the way for an Sn2 displacement with potassium thiophen-oxide, and sulfide oxidation to obtain phenylsulfone 5. Metallation of 5 was accomplished at —78°C with M-butyllithium in tetrahydrofuran (THF). The resulting a-phenylsulfonyl anion added readily to aldehyde 8 to afford a mixture of P-alkoxysulfones that underwent smooth O-acylation with acetic anhydride. The mixture of p-acetoxysulfones so formed was then reacted with 6% Na/Hg amalgam in methanol and ethyl... 

Chloro-3-methylpyrazine undergoes the expected reactions with aniline, methylaniline, sodium phenoxide, and sodium thiophen-oxide.304 Normal products of substitution are also obtained with piperidine and other heterocyclic amines such as pyrrolidine.305 However, when 2-chloro-3-methylpyrazine (98) is treated with sodamide in liquid ammonia 2-chloro-3-(3 -methyl-2 -pyrazylmethyl)-pyrazine (99) is produced as indicated (Scheme 29) in 70% yield.304... 

An indirect method for the synthesis of aryl alkyl sulhdes involves treatment of an aryl halide with butyllithium and then elemental sulfur. The resulting thiophen-oxide anion reacts with an alkyl halide to give the targeted sulhde. °... 

Oxidation of sulfur compounds. Xanthates are converted to sulfines, and i-butylsulfmamides to sulfonamides. Thus, amines can be protected via sulfmylation, and the sulfonamides are cleaved by TFA or TfOH. Thiophene oxides are obtained when thiophenes are treated with MCPBA-BFj OEtj. ... 

Cleavage of an 5-2-nitrobenzyl phosphorothioate is achieved with thiophen-oxide in 5 min." ... 

An exotic organomolybdenum complex derivative of terthiophene 44 was found to be electropolymerizable to give a thin electrochromic film with two Mo-centered oxidations superimposed upon the thiophene oxidation. The film switched between purple (undoped) and transparent blue (doped). These colors are quite different from... 

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