Dibenzothiophene sulfoxide

The fragmentation of dibenzothiophene sulfoxide resembles that of dibenzothiophene rather than that of the sulfone. This is due to primary loss of 0 to give the dibenzothiophene ion, which is the strongest feature of the spectrum. Much of the breakdown which follows is due to that of the dibenzothiophene ion. There are, however, some aspects of sulfone behavior, notably the formation of the dibenzofuran ion (14) by the loss of sulfur from the rearranged molecular ion (13). ... 

There have been a few reports of aerobic bacterial species which will grow on dibenzothiophene as their sole carbon source (51,52)- However, most studies have focused on its co-metabolism (22,52,54) which appears to be a more common phenomenon. Intermediates of the biodegradation have been identified in a number of studies (55-57). Figure 10 is a simplification of the proposed pathway for dibenzothiophene metabolism showing the two endproducts 3-hydroxy-2-formylbenzothiophene (HFBT), which is the more abundant, and dibenzothiophene-sulfoxide. [For a more complete pathway see (56) or (58)1. This pathway shows 1,2-dihydroxydibenzothiophene as an intermediate and this is analogous to the diols found as intermediates of aromatic hydrocarbons. 

None of the pure cultures that produced HFBT have been shown to further metabolize this compound. Bohonos et al. (46) found two further oxidation products, 3-hydroxybenzothiophene and 2,3-dihydrobenzothiophene-2,3-dione in aerobic mixed cultures co-metabolizing dibenzothiophene. Recently, Mormile and Atlas (61) inoculated portions of the filter-sterilized supernatant from a dibenzothiophene-degrading culture with soil and sediment samples and observed the loss of HFBT using a spectroscopic method. Under their aerobic growth conditions, they also observed the release of carbon dioxide from these cultures indicating that these products of dibenzothiophene degradation can be further oxidized. In addition, they observed carbon dioxide production from dibenzothiophene-sulfoxide. 

Ten milliliters of fuming nitric acid (sp. gr. 1.5) is added dropwise to a solution of 10 g. (0.054 mole) of dibenzothiophene (p. 101), in 80 ml. of glacial acetic acid at room temperature. The mixture is stirred for an hour and then poured into water. The precipitated solid is removed and extracted with hot ethanol until the melting point of the residue is about 180°. This residue is then recrystallized from benzene to give a 40% yield of product melting at 186°. The ethanol extraction removes dibenzothiophene sulfoxide also formed in 40% yield. 

The Jenks laboratory has investigated two other mechanisms for sulfoxide deoxygenation, but all of the work has been on dibenzothiophene sulfoxide 9 [99,100]. It is conceivable, given other properties of this molecule [101], that 9 is an exceptional case. First, one additional considered possibility is that the sulfoxide undergoes a hydrogen abstraction, followed by hydroxyl transfer by 199 to the resultant solvent radical. 

Evidence for the formation of singlet oxygen from Posner was based on chemical trapping. Photolysis of dibenzothiophene sulfoxide in a 90 10 mixture of cyclohexene and acetic acid provided a sample that tested positive for peroxides. After reduction with Nal, 2-cyclohexenol was obtained in 22-34% yield. The authors noted a lack of cyclohexanone and cyclohexene epoxide. This was rationalized as outlined below [97]. 

Tf20 in combination with sulfoxides lacking a-protons, such as diphenylsulfoxide or dibenzothiophene sulfoxide, generates a sulfoxonium triflate, which is capable of effecting the formation of glycosides from carbohydrate hemiacetals and oxygen nucleophiles. This is a dehydrative glycosylation, and appears to proceed by way of a sulfoxonium intermediate (eq 72). ... 

Better understanding of the mechanism of biodesulfurization, as shown in Figure 8, may be gained from some recent studies ° Gallagher et al. reported a sulfur-specific pathway in microbial desulfurization of DBT. Rhodococcus rhodochrous strain IGTS8 metabolizes DBT in a sulflir-specific manner. Two routes of desulfurization have been identified. Under growth conditions, the intermediates are dibenzothiophene sulfoxide, dibenzothiophene sulfone, 2 -hydroxybipheny 1-2-sulfonate, and 2,2 -... 

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