Sulfur containing benzo thiophenes

Competitive metallation experiments with IV-methylpyrrole and thiophene and with IV-methylindole and benzo[6]thiophene indicate that the sulfur-containing heterocycles react more rapidly with H-butyllithium in ether. The comparative reactivity of thiophene and furan with butyllithium depends on the metallation conditions. In hexane, furan reacts more rapidly than thiophene but in ether, in the presence of tetramethylethylenediamine (TMEDA), the order of reactivity is reversed (77JCS(P1)887). Competitive metallation experiments have established that dibenzofuran is more easily lithiated than dibenzothiophene, which in turn is more easily lithiated than A-ethylcarbazole. These compounds lose the proton bound to carbon 4 in dibenzofuran and dibenzothiophene and the equivalent proton (bound to carbon 1) in the carbazole (64JOM(2)304). 

Benzo[ >]thiophene dianion (173) has been prepared by reduction of benzo[ >J thiophene with sodium metal at - 78°C in [2H8]THF. The H and 13C NMR spectra of the purple solution obtained prove that it is the dianion and not a radical anion. This is the first example of a sulfur-containing (4n)Tr polycyclic dianion. The dianion undergoes oxidation to benzo[ ]thiophene with oxygen (85CC1033). 

Unwanted sulfur-containing components may be removed from petroleum oils by hydrodesulfurization over a Co-Mo catalyst at high temperatures under pressure ( unifining or hydrofining ).38 However, benzo[6]thiophene is hydrodesulfurized with difficulty over a molybdenum catalyst89 40 and it is difficult to remove completely from petroleum oils by hydrofining.41... 

Photodimerizations have been observed in a variety of sulfur-containing heterocycles notable examples include the photodimerization of 2- and 3-ary lbenzo[b]thiophens,287 benzo[h]thiophen 1-oxide,288 benzo[h]thiophen 1,1-dioxide,289 and its 2-bromo289 and 2-methyl derivatives.290 All four possible dimers were obtained on irradiation of thio-chromone in aromatic solvents,291 and 1-thiauracil (345) is converted into... 

Ab initio MO calculations have been carried out on benzo[. ]thiophene (BT), 2-methylbenzo[/ ]thiophene (2-MeBT), 3-methylbenzo[ ]thiophene (3-MeBT), and a number of organometallic complexes containing these thiophenic moieties in an attempt to understand the usual preference for insertion of metal fragments into the sulfur-carbon(vinyl) bond of BT and the recent observations of insertion into the sulfur-carbon(aryl) bond <19980M3798>. 

Dianions derived from sulfur and oxygen containing polycyclic systems have not been reported until very recently. The weak carbon-sulfur bond could discourage attempts to prepare such dianions. Sulfur removal studies by alkali metals were successful due to the properties of the carbon-sulfur bond 182,183). Reductive alkylation studies on model compounds which are relevant to sulfur containing systems demonstrated the stability of hydrocarbon dianions 182). A spectroscopic study performed under mild conditions afforded the characterization of sulfur and oxygen containing dianions 184 186). Benzo[b]thiophene, (73), 1,3-diphenylbenzo[c]thiophene (74) and l,3-diphenylbenzo[c]furan (75) form the respective dianions at low temperature. 

Sulfur-containing compounds These may be thiols, sulfides, thiophenes, benzo- and dibenzo-thiophenes, and more complex structures. Solvent extraction reduces measured sulfur levels and therefore the content of sulfur compounds in solvent refined lubes in solvent refined lubes, oxidation studies show that there appears to be an optimum level for sulfur compounds. Lube hydrocracking generally will reduce sulfur to about 10 ppm or less in the base stocks. The 4,6-di-alkyl... 

Hydrodesulfurization [HDS, Eq. (1)] is the process by which sulfur is removed from fossil materials upon treatment with a high pressure of H2 (3.5-17 MPa) at high temperature (300-425 °C) in the presence of heterogenexius catalysts, generally transition metal sulfides (Mo, W, Co, Ni) supported on alumina [1]. About 90% of the sulfur in fossil materials is contained in thiophenic molecules, which comprise an enormous variety of substituted thiophenes, and benzo[b]thiophenes, di-benzo[b,d]thiophenes as well as other fused-ring thiophenes, most of which are generally less easily desulfurized over heterogeneous catalysts than any other sulfur compound in petroleum feedstocks (e.g., thiols, sulfide, and disulfides). 

Figure 2. Flame photometric detection of sulfur-containing volatiles from O.lg of cooked ground-beef, top left), beef cooked to an end-point temperature (EPT) of 70° C. Sample was purged at 50° C in the SPTD the same day it was prepared, top, right), same as the top, left but the sample was stored for 4 days, bottom, left), beef cooked to an EPT of 70° C. Sample was purged at 100° C in the SPTD the same day as it was prepared, bottom, right), same as the bottom, left but the sample was stored for 4 days. B = benzo-thiophene external standard.

When benzyl halides, benzylidene halides, benzotrichloride, or aryl-substituted haloethanes are heated with sulfur, complex mixtures containing thiophenes, benzo[6]thiophenes, and other condensed... 

There is surprisingly little reliable information on the sulfonation of benzo[6]thiophene or its derivatives. Benzo[6]thiophene is more readily sulfonated than naphthalene.699 Reaction with concentrated sulfuric acid at 80° gives a mixture of mono-, di-, and trisulfonic acids, reaction with 70% sulfuric acid at 80° gives a monosulfonic acid,699 and reaction with 18% oleum gives a disulfonic acid 86 in each case the orientation of the products is unknown. Treatment of benzo[6]thiophene with concentrated sulfuric acid in acetic anhydride at 20° gives 3-acetylbenzo[6]thiophene (ca. 10%) and a sulfonation product (isolated as the potassium salt), which was believed to be the 3-sulfonic acid.660 Recently, the sulfonation product has been shown to contain the 2- (8%) and 3-isomer (92%), by conversion into the sulfonyl chlorides and reduction to a separable mixture of 2- and 3-mercaptobenzo[6]thiophene.84... 

Oil sand asphaltenes pyrolysis oil also contain n-alkane-derived cyclic sulfides along with /z-alkane-derived thiophenes, benzo- and dibenzothiophenes, showing that the precursor oil was of n-alkanoic origin. Approximately 25% of the sulfur in these asphaltenes is in the form of sulfides. 

Cava and Pollack s elegant synthesis of benzo[c]thiophene52 has been extended to the synthesis of, for example, naphtho[l,2-c]thio-phene (47),52 methyl benzo[c]thiophene-5-carboxylate,54 and 1,3-dimethyl- (48)55 and l,3,4,6-tetraphenylthieno[3,4-c]thiophene (49).56 The last compound is of particular interest because it is a remarkably stable (cf. compound 48 which only exists transiently) nonclassical thiophene containing ten n electrons for which the only uncharged resonance structure (49) contains a tetravalent sulfur atom. When the sulfoxide (50) is pyrolyzed over aluminum oxide, it gives the parent cyclic sulfide and 51 by disproportionation.57 However, when 50 is heated in acetic anhydride in the presence of iV-phenylmaleimide,... 

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