Dibenzothiophene structure

Protoporphyrin-IX, N-methyl-, 4, 396 Protoporphyrins, 4, 382 photooxygenation, 4, 402 Prototropic tautomerism polyheteroatom six-membered rings, 3, 1055 Prozapine properties, 7, 545 Pschorr reaction carbolines from, 4, 523 dibenzazepines from, 7, 533 dibenzothiophenes from, 4, 107 phenanthridines from, 2, 433 Pseudilin, pentabromo-synthesis, 1, 449 Pseudoazulene synthesis, 4, 526 Pseudobases in synthesis reviews, 1, 62 Pseudocyanines, 2, 331 Pseudothiohydantoin synthesis, 6, 296 Pseudouracil structure, 3, 68 Pseudoyangonin IR spectra, 3, 596 Pseudoyohimbine synthesis, 2, 271 Psicofuranine biological activity, 5, 603 as pharmaceutical, 1, 153, 160... 

Of some relevance in this connection is a study216 on the structure of the anion radicals formed when diaryl sulphones react with n-butyllithium in hexane-HMPA solution under an argon atmosphere. Apparently, a dehydrogenative cyclization and a further one-electron reduction occurs to produce the anion radicals of substituted dibenzothiophene-S, S-dioxides. These anion radicals were studied by ESR spectroscopy. 

Under anaerobic conditions dibenzothiophene is metabolized to a carboxybenzothiophene whose structure has not been established (Annweiler et al. 2001). 

Two strains were isolated and purified, Pseudomonas sp. CDT-4, and Nocardia aster-oides, CDT-4b (ATCC 202160 and 202161, respectively). The microbes were passed through a multiple screen, first to allow growth on dibenzothiophene (DBT) as a sole source of sulfur, and then on fossil fuels, to identify organisms capable of desulfurization without metabolizing the DBT phenyl ring structures. N. asteroides sp. CDT-4b was found to metabolize DBT. The Pseudomonas species was found to utilize trace levels of sulfate from media and was found to be incapable of growth on DBT as a sole source of sulfur. However, the co-culture could remove more than 20% sulfur, with supplementation of a second sulfur-free carbon source. 

Probably the most important recent advance in the chemistry of dibenzothiophene has been the adoption of NMR techniques for structural determination. This will eliminate much of the tedious synthetic work which was previously needed to establish the structure of new derivatives. 

The spin-spin coupling constants for the spectrum of dibenzothiophene in carbon tetrachloride and acetone have been accurately determined by computer analysis and listed. In routine structural studies of derivatives of dibenzothiophene it is usually found that ortho-couplings are close to 8 Hz, meta couplings about 2 Hz and between 0.5 and 1 Hz. In chloroform-dj, H-2 and 3 in dibenzothiophene have the same chemical shift and the spectrum of 1,4-dimethyldibenzothiophene in this solvent also shows H-2,3 as a singlet at 87.03. Apart from the minimal coupling which has been detected between H-1,9 of 0.08 Hz, no interring coupling is observed in dibenzothiophenes. 

Sawicki, in 1954, deduced the structure of a number of mono- and disubstituted dibenzothiophenes by spectral comparison with known TT-isoelectronio derivatives of carbazole and thereby established the foundations for general structure determination of unknown derivatives of both dibenzothiophene and dibenzoselenophene. - This approach has now been largely replaced by NMR techniques however, general... 

Proton hyperfine structure at magnetic fields below 100 G in electron magnetic resonance absorptions by oriented triplet dibenzothiophene has been obtained in biphenyl single crystals. ... 

With the exception of 4-methoxydibenzothiophene, which is well characterized, the literature concerning the remaining three mono-methoxy compounds is somewhat confused. As mentioned earlier (Section III, C, 3), dibenzothiophene is metabolized as 1 -hydroxydibenzo-thiophene 5,5-dioxide, which was converted to the corresponding methoxy compound by methylation for structure determination. The position of the methoxy group was determined by the fact that the melting point of the product was different from those of the other three methoxy sulfones, each of which was listed for the first time, but without details of source or preparation. Tilak had attempted the preparation of... 

As mentioned earlier, oxidation of dibenzothiophene to either the sulfoxide or sulfone causes electrophilic attack to occur at the 3-position rather than at the normal 2-position. This trend is further exemplified by the behavior of 4-methyldibenzothiophene which is nitrated in the 2-position (26%), while nitration of 4-methyldibenzothiophene 5,5-dioxide occurs in the 3-position yielding 112. The structures of both of these products were deduced from their NMR spectra. 

Friedel-Oafts diacylation of dibenzothiophene with 7-oxo-lH-benzo[d,e]anthracene-3-carbonyl chloride, followed by ring closure in molten sodium chloride-aluminum chloride, is reported to yield 131 which is claimed to be useful as an orange dyestuff. No evidence for the structure of 131 was presented although analogous succinoylation studies (Section VI,G,2) would indicate that the structure is correct. 

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