Thiophenes into dibenzothiophenes

By treatment with CHCl2OMe or Et0CCI2C02Et in the presence of SnCl4, 2-allylbenzo[b]thiophene is converted into dibenzothiophene or its... 

Hydroprocessing of fossil fuel feedstocks for the removal of sulfur, nitrogen, and residual metals is a large-scale refinery process. Sulfru in fossil materials is found in various compounds, such as thiols, sulfides, disulfides, thiophenes, benzo-thiophenes, and dibenzothiophenes. The removal of sulfur from these fossil materials is commonly referred to as hydrodesulfurization (HDS), which is important in order to reduce the amount of sulfur introduced into the atmosphere since this contributes to acid rain. Secondly, the poisoning of catalysts in downstream processing has to be reduced. 

The System described in the previous section has been extended with a sulfur chemiluminescence detector (SCO) for the detection of Sulfur compounds (32). The separated fractions were thiols + sulfides + thiophenes (as one group), benzothio-phenes, dibenzothiophenes and benzonaphtho-thiophenes. These four groups have been subsequently injected on-line into and separated by the GC unit. Again, no overlap between these groups has been detected, as can be seen from Figure 14.20, in which the total sulfur compounds are shown and from Figure 14.21 in which the separated dibenzothiophenes fraction is presented. The lower limit of detection of this method proved to be 1 ppm (mg kg ) sulfur per compound. 

The synthesis of the four monocarboxylic acids of dibenzothiophene has been recorded in the previous review. However, several modified preparations have since been described. Ethyl 1-dibenzothiophene-carboxylate has been synthesized from 2-allylbenzo[6]thiophene (Section IV,B, 1) hydrolysis afforded the 1-acid (57% overall). In a similar manner, 3-methyl-1-dibenzothiophenecarboxylic acid was obtained from the appropriately substituted allyl compound. This method is now the preferred way of introducing a carbon-containing substituent into the 1-position of dibenzothiophene. 2-Dibenzothiophenecarboxylic acid has been prepared by oxidation of the corresponding aldehyde or by sodium hypoiodite oxidation of the corresponding acetyl compound. Reaction of 2-acetyldibenzothiophene with anhydrous pyridine and iodine yields the acetyl pyridinium salt (132) (92%), hydrolysis of which yields the 2-acid (85%). The same sequence has been carried out on 2-acetyldibenzothiophene 5,5-dioxide. The most efficient method of preparing the 2-acid is via carbonation of 2-lithio-... 

Microbial degradation of the aromatic nucleus of substituted thiophenes has been demonstrated by Amphlett and Calley (12). Dibenzothiophene is converted into a water-soluble form, 3-hydroxy-2-formylbenzothiophene which imparts an orange-red color in the culture broth. Finnerty ( 13) reported the use of microorganisms of the genus Acinetobacter and Micrococcus to convert dibenzothiophenes into water-soluble products that can be removed from high-sulfur crude oil. 

Eisch et al. (24) performed a mechanistic study of the desulfurization of dibenzothiophene by a nickel(0)-bipyridyl complex and reported that a radical anion of the thiophene nucleus was formed and underwent C-S bond cleavage into S and an aromatic radical. In addition, they suggested that the oxidative reaction of the nickel(0)-bipyridyl complex toward dibenzothiophene had the characteristics of stepwise electron transfer rather than nucleophilic attack. However, no correlations occurred between the desulfurization rate and the reaction indexes of Fr(E), Fr(N), and Fr(R), as shown in Table II. The results suggested no evidence for either electron transfer or nucleophilic attack in this study. Moreover, the radical reaction was not... 

Carbon-sulfur bond breaking was observed while treating thiophene with Cp"Co(C2H4)2 at 70 °C in benzene. A cobalt metal center had inserted into the C-S bond and a second Cp Co unit had complexed to the cobalt, sulfur, and C-C double bond 330. Further reaction of the resulting compound with H2S produced a new butadiene dithiolate compound, in which a sulfur atom has been inserted into the metal-carbon bond 331. Reaction with dibenzothiophene produced an analogous dinuclear C-S insertion-reaction adduct (Equation (54)). ... 

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