Dibenzothiophenes, oxidation

It was shown that dibenzothiophene oxide 17 is inert to 1-benzyl-l,4-dihydro nicotinamide (BNAH) but that, in the presence of catalytic amounts of metalloporphyrin, 17 is reduced quantitatively by BNAH. From experimental results with different catalysts [meso-tetraphenylporphinato iron(III) chloride (TPPFeCl) being the best] and a series of substituted sulfoxides, Oae and coworkers80 suggest an initial SET from BNAH to Fe1 followed by a second SET from the catalyst to the sulfoxide. The results are also consistent with an initial coordination of the substrate to Fem, thus weakening the sulfur-oxygen bond in a way reminiscent of the reduction of sulfoxides with sodium borohydride in the presence of catalytic amounts of cobalt chloride81. 

The usual range of reactions has been recorded for the aldehydes of dibenzothiophene. Oxidation yields the corresponding acid, - reduction with LAH the corresponding alcohol, reduction under Huang-Minlon conditions the corresponding methyl compound, and two examples of the Cannizarro reaction have been described. ... 

Photodeoxygenation reaction was obtained also on dibenzothiophene oxide (01JOC4576 03JCR(S)60). 

Benzothiophene. There have been several reports on the aerobic co-metabolism of benzothiophene (42, 46, 47). Bohonos et al. (46) identifed some benzothiophene metabolites by GC-MS and the structures of these are shown in Figure 8. Although the only compounds found were oxidized on the thiophene ring, they could not exclude the possibility of oxidation of the benzene ring. Finnerty et al. (48) found that benzothiophene was transformed to unidentified water-soluble products by a dibenzothiophene-oxidizing bacterium. 

Other Organosulfur Compounds. There have been reports of the microbial metabolism of other OSC. However, few of these studies have given the identities of intermediates or organic endproducts of the OSC. For example, aerobic cultures have been reported to remove sulfur from phenyl sulfide (62). Thioxanthene and thianthrene were transformed to water-soluble products by a dibenzothiophene-oxidizing bacterium (48). In addition, thianthrene and thioxanthene served as sole carbon sources for the aerobic thermophile S. acidocaldarius (69) which released sulfate from these compounds. 

Montiel C, Terres E, Dominguez JM et al (2007) Immobilization of chloroperoxidase on silica-based materials for 4,6-dimethyl dibenzothiophene oxidation. J Mol Catal B Enzym 48 90-98... 

Fig. 2. Common pathway of naphthalene and dibenzothiophene oxidative hydrocarbon degradation.

Figure 15.7. Alkyl-dibenzothiophene oxidation to the corresponding sulfone.

Huang TH, Whang WT, Shen JY, Wen YS, Lin JT, Ke TH, Chen LY, Wu CC (2006) Dibenzothiophene/oxide and quinoxaline/pyrazine derivatives serving as electron-transport materials. Adv Fund Mater 16 1449-1456... 

Cytochrome c, myoglobin, hemoglobin. Si02 Dibenzothiophene oxidation 311... 

No oxidizing agent is required for the sulfuric acid promoted cyclization of iV,iV-diphenyl-hydroxylamine to carbazole (13CB3304). The parallel conversion of diphenyl sulfoxide and diphenyl selenoxide to dibenzothiophene (23CB2275) and dibenzoselenophene (39CR(199)53l) is effected by treatment with sodamide. 

Dibenzothiophene S-oxide Dibenzothiophene S, S-dioxide Dibenzothiophene S, S-dioxide... 

Oxidation of thiophene with Fenton-like reagents produces 2-hydroxythiophene of which the 2(570 One isomer is the most stable (Eq. 1) <96JCR(S)242>. In contrast, methyltrioxorhenium (Vn) catalyzed hydrogen peroxide oxidation of thiophene and its derivatives forms first the sulfoxide and ultimately the sulfone derivatives <96107211>. Anodic oxidation of aminated dibenzothiophene produces stable radical cation salts <96BSF597>. Reduction of dihalothiophene at carbon cathodes produces the first example of an electrochemical halogen dance reaction (Eq. 2) <96JOC8074>. 

The enzyme in Rhodococcus sp. strain IGTS8 that brings about successive oxidation of dibenzothiophene to the sulfoxide and the sulfone is a flavin mononucleotide-dependent monooxygenase that carries out both reactions by sequential incorporation of a single atom of oxygen from Oj (Lei and Tu 1996). 

Bezalel L, Y Hadar, PP Fu, IP Freeman, CE Cerniglia (1996c) Initial oxidation products in the metabolism of pyrene, anthracene, tluorene, and dibenzothiophene by the white rot fungus Pleurotus ostreatus. Appl Environ Microbiol 62 2554-2559. 

Resnick SM, DT Gibson (1996) Regio- and stereospecific oxidation of fluorene, dibenzofuran, and dibenzothiophene by naphthalene dioxygenase from Pseudomonas sp. strain NCIB-4. Appl Environ Microbiol 62 4073-4080. 

Kodama K, K Umehara, K Shikmizu, S Nakatani, Y Minoda, K Yamada (1973) Identification of microbial products from dibenzothiophene and its proposed oxidation pathway. Agric Biol Ghent 37 45-50. 

Although single-electron-transfer (SET) processes would be expected to be important in reactions that use metals as reagents, this type of process has also been recognized in the reduction of carbonyl groups that involve 1,4-dihydronicotinamide derivatives . Recent work by Oae and coworkers" has shown that an SET process is operative in the reduction of dibenzothiophene S-oxide by l-benzyl-l,4-dihydronicotinamide when the reaction is catalyzed by metalloporphins. The reaction is outlined in equation (18), but the study gave results of much more mechanistic than synthetic value. This type of study is relevant to understanding biochemical mechanisms since it is known that methionine sulphoxide is reduced to methionine by NADPH when the reaction is catalyzed by an enzyme isolated from certain yeasts . 

IGTS8 or simply IGTS8. The metabolic pathway in Rhodococcus sp. IGTS8 was delineated in the early 1990s [62], The pathway consists of four enzymes. DBT is converted to 2-hydroxybiphenyl (HBP) and sulfite via a 4-step pathway and the following intermediates DBT sulfoxide (dibenzothiophene-5-oxide, DBTO), DBT sulfone (dibenzothiophene-5,5-dioxide, DBT02) and hydroxyphenyl benzene sulfonate (phenol-phenyl sulfinate, HBPSi). 

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