Thianthrene, formation

Thianthrene, formation in thermal reactions of thiyl radicals 90UK1338. Thianthrenes, general review 90AHC(48)301. 

More recently, thianthrene was synthesized from 1,2-dichlorobenzene with hydrogen sulfide at 550 C. This method is of particular interest since it demonstrates thianthrene formation in high yields from chloro-displacement reactions, and more importantly indicates thermal stability of the thianthrene nucleus well into the upper temperature range for high-performance polymers. 

The formation of adduct is followed by fragmentation and subsequent H-atom abstraction reaction from the sulfinic acid produced. Strong acid solutions of aromatic sulfoxides like thianthrene 5-oxide (7) or phenothiazine 5-oxide (8) gives rise to ESR signals, which... 

The introduction of substituents into the 1- and 2- positions of thianthrene can be achieved by deprotonation at C-1 and subsequent reaction with electrophiles and by formation of 2-lithiothianthrene from the corresponding bromo compound <96JCS(P1)2391>. Selective oxidation of both thianthrene and its 5-oxide have been described <96CEJ255, 96JCS(P1)2693>. 

Some 5-(alkyloxy)thianthrenium perchlorates (15) have been prepared in which the alkyl group may be primary or secondary. Reaction with iodide ions may result in 5 n2 reaction at the alkyl group or NAr reaction at the sulfonium sulfur atom leading to the formation of thianthrene. ... 

The formation of the thianthrene cation-radical complex with anisole, that is, (HetH) + ArH (HetH---ArH)+ ... 

Treatment of dibenzothiophene with diphenylsilane under reflux for 6 days gave starting material (84%) and tetraphenylsilane (16%). In related heterocycles, such as thianthrene, low yield replacement of sulfur by diphenylsilicon occurs, and in this case the formation of tetraphenylsilane may be indicative of the intermediacy of such an insertion product which then undergoes carbon-carbon bond fission. ... 

The magenta appearance of the paramagnetic solution produced by dissolving thianthrene in c. sulfuric acid is due to the absorbance of the thianthrene radical ion(l-l-) (T " ") (4) formed by one-electron oxidation. Even before this was understood, the formation of such deep colors on disolution in c. sulfuric acid was used as a diagnostic test for a thianthrene ring system. 

Molecular ions obtained from thianthrenes are normally the base peak in their mass spectra. The principal fragmentation involves loss of sulfur (87PS377), and this is interpreted as formation of a dibenzothiophen radical cation (16). Further loss of sulfur then occurs. CSH is lost from both the dibenzothiophen fragment ion and from the molecular ion species such as 17, from the parent ion, are proposed (74JHC287). The mass spectroscopic fragmentation pattern of fluorothianthrenes is comparable (720MS373). 

Electrophilic substitution of thianthrene takes place at C-2. No examples of even minor amounts of 1-mono-substituted product have been reported. Disubstitution gives 2,7- (usually) or 2,8-products. In a few cases, 2,6-derivatives have been claimed. The presence of a sulfoxide or sulfone unit greatly reduces the susceptibility of either ring to electrophilic substitution. Carbon-centered electrophilic addition to sulfur to produce 5-R-thianthrenium salts has been described rarely most examples of the formation of such salts have involved the thianthrene radical ion(l-t-). Treatment of thianthrene with alkyl/aryllithiums produces the 1-lithio-species, and these organometallic derivatives allow the introduction of substituents at this position. 

Early attempts to nitrate thianthrene showed 5-oxidation to proceed more rapidly than C-nitration, both 5-mono- and 5,10-dioxides being available in this way. Production of these, and tri- and tetroxide formation, were already well-studied processes by 1960 (66HC1155). 

Treatment of thianthrene with S/AICI3 at only 80°C gives polymeric materials of the form in 12 (Section II,D), the formation of which probably involves electrophilic attack by sulfur catalyzed by the Lewis acid (85MI2 88MI3). 

Azoadamantane exposed to 2 mol equivalents of T CIO4 at room temperature rapidly and quantitatively evolved nitrogen, and thianthrene and products derived from the adamantyl cation were obtained. Equations (38)-(40) (AA, azo-adamantane Ad, adamantane) make clear why 2 mol equivalents of the radical oxidant are required (85JA2561). The comparable interaction of T with phenylazotriphenylmethane and di-ter/-butyl diazene, using a 2 1 ratio of radical cation to substrate, also leads to the formation of thianthrene and nitrogen (85PS111). 

An intriguing use of the oxidative potential stored in thianthrene radical ion(l-l-) is provided by the formation of high-energy phosphate bonds. Thus, the interaction of adenosine-5 -phosphate (AMP) and orthophos-phoric acid, each as their ammonium salts, with two equivalents of thi-... 

At the time of the earlier review (66HC1155), it was already known that combinations of arenes with sulfur, or with sulfur mono- or dichlorides in the presence of Lewis acids (IV,B,1), or of aryl thiols, diaryl sulfides, or disulfides (IV,B,2 and 3) again heated with Lewis acid catalysts, generate thianthrenes, sometimes in acceptable preparative yields. A complimentary method is the treatment of aryl thiols with c. H2SO4. Routes from arenes and aryl thiols almost certainly involve the initial formation of diaryl sulfides. All these methods inevitably give symmetrical thianthrenes carrying identical substituents on each benzene ring (Scheme 9), unless the second sulfur is introduced in a controlled fashion into a preformed, unsymmetrical diphenyl sulfide. 

Benzyne generated from 2-carboxybenzenediazonium chloride reacted with sulfur monochloiide to give dibenzothiophene 13 (8-10%) and thiantherene 14 (26-35%) (1989SUL83). A mechanism involving the addition of sulfur mono-chloride to benzyne with the formation of betaine 15 followed by the elimination of SCI2 to afford benzothiirene 16 and a further reaction with another benzyne molecule or dimerization to thianthrene 14 is given in Scheme 8. 

Electrocatalytic formation of Me SO from DMSO was effected using cw-[Ru(0) (py)(bpy)2] VPt electrode/water-DMSO cf. mech. Ch. 1 [113], Oxidation of thian-threne-5-oxide by RuO /aq. Na(IO )/CCyO°C gave a mixture of the sulfone and thianthrene-5,5-dioxide with minor amounts of the disulfoxide and also thian-threne-5,5,10-trioxide comparisons were made between the behaviour of RuO, CrOjClj and [MnO ] for these reactions cf. mech. Ch. 1) [114]. 

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>. 

Another aspect of the reactivity of the sulfur atom is illustrated by a reaction done on thianthrene. Indeed, 8 is not sufficiently nucleophilic to be alkylated by methods that work well with dialkyl and alkyl aryl sulfides, although Saeva was able to alkylate it by reaction with -cyanobenzyl bromide and silver triflate <1986T6123>. The sulfonium salt 52 bearing a methyl group can be obtain by an acid-promoted reaction with methyl formate (Equation 4) <1998JCX37522>. 

Condensation of copper salts of acetylenes (240) with o -bromobenzenethiol (239) by slow addition of a pyridine solution of (239) to a dilute pyridine solution of (240) under nitrogen at 110 °C for 24 hours gave the corresponding benzo[6]thiophenes (241) with the following yields R = H, 90% R = Bun or Prn, 80% R = C02Et, 35%. Formation of thianthrene by dimerization of the copper salt of (239) was a competing reaction which became the major pathway in more concentrated solutions. 

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