Thianthrene chlorination

Exhaustive chlorination of thianthrene yields a mixture of polychloro-derivatives, the main component being 2,3,7,8-tetrachlorothianthrene (77USP3989715). In a survey, authors looking for dioxinlike activity in sediment from a sanitary sewer near a chemical factory detected tetrachlo-rothianthrene using gas-liquid chromatography and mass spectrometry (85MI4). 

Phenoxathiin and thianthrene can be chlorinated without oxidation into the corresponding sulfoxides using sulfuryl chloride and AICI3 to form the 2,3,7,8-tetrachloro derivatives 41 and 42, respectively. Use of BMS reagent- a mixture of sulfur monochloride, sulfuryl chloride, and aluminium chloride - results in exhaustive chlorination of phenoxathiin and thianthrene with formation of perchlorinated products 43 and 44. It is noteworthy that using sulfuryl chloride in dichloromethane, the sulfoxides were isolated as the major products <1997CHE333>. 

OCTA and HeptaCTAs are formed, along with other polychlorinated aromatic sulfur compounds, as by products in the synthesis of pentachlorothiophenol from hexachlorobenzene. Pentachlorothiophenol is used as an additive for the improvement of the vulcanization process of rubber in the tire industry. The formation of OCTA is believed to occur by dimerization of pentachlorothio-phenate and by intramolecular cyclization and the formation of HeptaCTAs by dechlorination of higher chlorinated thianthrenes [27]. 

PCTAs can be prepared by chlorination of thianthrene. The method of Buckholtz uses sulfuryl chloride as a chlorination agent in a mixture of o- and p-chlorotoluene [34]. For environmental studies small amounts of 2378-TeCTA and some other PCTAs have been prepared by a modified method of Buckholtz... 

TriCTAs and TeCTAs were prepared by stepwise addition of sulfuryl chloride over 4 h at 60°C. The degree of chlorination was found to be three to four (only tri- and tetrachlorinated thianthrenes were observed as reaction products) when all of the parent compound was consumed. One TriCTA and one TeCTA were obtained as main products. In addition, two other TriCTAs, four TeCTAs, and some PeCTAs were observed in minor concentrations. Because of the ortho- and para-directing properties of sulfur in electrophilic aromatic substitution reactions, 237-TriCTA and 2378-TeCTA, the thio analogue of 2378-TeCDD, were obtained as the main products. Mass spectrometry and H NMR were used in the structure verification. 

Reaction of chloride ion with 1 resulted in part in electron exchange since some chlorine was removed by nitrogen flow and was assayed (9%). Thianthrene (47%), thianthrene 5-oxide (18, 33%) and a very small amount (0.3%) of 2-chlorothianthrene (19) were also obtained ( ). Since molecular chlorine slowly chlorinates thianthrene and since thianthrene 5-oxide can be prepared by oxidation of thianthrene with chlorine in wet solvents, the cation radical results are thought to fit together (eqs. 34-37). Nevertheless a proper kinetic and mechanistic study needs to be made. 

Formation of the thianthrene moiety evidently involves two routes since both possible derivatives are formed in equal amounts. Displacement of the 3,3 -chlorine substituents of 14 with Na2S directly yields thianthrene substituted in the 2,8-position. Thioether scrambling of 14 with Na2S followed by subsequent formation of vicinal sulfide bonds is required to explain formation of thianthrene substituted in the 2,7-positions. Thioether exchange in the intermediate is possible due to the activating influence of amide functionality which strongly influences initial thioether formation. Ether exchange with sulfur nucleophiles has been quite effective for other systems which are activated for nucleophilic aromatic substitution. ... 

Thianthrene-di-, tri-, and tetracarboxylic acids, and a variety of their derivatives, were prepared and polymerized with co-monomers to obtain thianthiene-containing polyimides, aramids and polybenzoxazoles. The multiply substituted thianthrene derivatives were prepared starting with dichloro-substituted benzamide or phthalimide via chlorine displacement by sulfur nucleophiles. The protected carboxyl groups enhanced the displacement reaction to give thianthrene bisamides and imides in good yields. Deprotection with base gave carboxylic acid derivatives. 

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