Thianthrenes carbon

Mislow and co-workers (258) and Hammond (259) have shown that optically active diaryl sulfoxides, which are configurationally stable in the dark at 200°C, lose their optical activity after 1 hr at room temperature on irradiation with ultraviolet light. Similarly, an easy conversion of the trans isomer of thianthrene-5,10-oxide 206a into the thermodynamically more stable cis isomer takes place upon irradiation in dioxane for 2 hr. However, the behavior of a-naphthylethyl p-tolyl sulfoxide under comparable irradiation conditions is different, namely, it is completely decomposed after 4 min. These differences are not surprising because the photochemical racemization of diaryl sulfoxides occurs by way of the pyramidal inversion mechanism whereas decomposition of the latter sulfoxide occurs via a radical mechanism with the cleavage of the sulfur-carbon bond. It is interesting to note that photoracemization may be a zero-order process in which the rate depends only on the intensity of the radiation and on the quantum yield. 

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. ... 

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. 

In a study of the carbonization (- 525°C) and graphitization (- 2500°C) of thianthrene in comparison with anthracene, it was shown that the carbons of the heterocycle are nongraphitable between 1200°C and 2500°C, sulfur was evolved continuously (85MI3). Aluminum chloride catalytic carbonization of thianthrene has also been studied. At lower temperatures than without a catalyst, thianthrene produced an isotropic coke catalytic co-carbonization with anthracene and 9,10-dihydroanth-racene gave mosaic and needle cokes, respectively (80MI6, 80MI7). Po-ly(arylene sulfides) were shown to be produced by aluminum chloride treatment of thianthrene at 180-350°C (79URP659582). 

The solid T salt which has been used in nearly all chemical studies is the EXPLOSIVE dark-reddish thianthrene radical ion(H-) perchlorate use of the salt in quantities greater than 50 mg is not advised (62JCS4963 69JOC3368). The salt is formed in 90% yield upon treatment of thianthrene with acetic anhydride/perchloric acid in carbon tetrachloride, at room temperature overnight. 

The oxidation of sulfides to sulfoxides (1 eq. of oxidant) and sulfones (2 eq. of oxidant) is possible in the absence of a catalyst by employing the perhydrate prepared from hexafluoroacetone or 2-hydroperoxy-l,l,l-trifluoropropan-2-ol as reported by Ganeshpure and Adam (Scheme 99 f°. The reaction is highly chemoselective and sulfoxidation occurs in the presence of double bonds and amine functions, which were not oxidized. With one equivalent of the a-hydroxyhydroperoxide, diphenyl sulfide was selectively transformed to the sulfoxide in quantitative yield and with two equivalents of oxidant the corresponding sulfone was quantitatively obtained. 2-Hydroperoxy-l,l,l-fluoropropan-2-ol as an electrophilic oxidant oxidizes thianthrene-5-oxide almost exclusively to the corresponding cw-disulfoxide, although low conversions were observed (15%) (Scheme 99). Deprotonation of this oxidant with sodium carbonate in methanol leads to a peroxo anion, which is a nucleophilic oxidant and oxidizes thianthrene-5-oxide preferentially to the sulfone. 

The proton spectra for the dibenzo derivatives, viz. dibenzo[6,e][l,4]dioxin, phenoxathiin and thianthrene, have been reported in full, as part of a wider survey of heterocyclic compounds structurally related to anthracene. The protons in dibenzo[6,e ][ 1,4]dioxin are the most shielded, and in phenoxathiin the protons ortho and para oriented to the C—O bond are shielded relative to those ortho and para to sulfur <740MR(6)U5). The 13C chemical shifts for phenoxathiin follow a similar pattern, with carbons ortho and para to the C—O bond resonating at 117.5 and 124.2 p.p.m. respectively, and at higher field than those ortho, para to the C—S bond (127.4 and 126.5 p.p.m.), in good agreement with shifts predicted on the basis of additivity effects <73JMR(12)143). 

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. 

Sulphur, or sulphur-containing heterocyclics induce the formation of cokes of small sized optical texture (22) Mochida et al. (75) examined the carbonization behaviour, in the presence of aluminium chlorides, of diphenyl sulphide, thioxanthene and thianthrene,... 

A ring carbon can also be involved, however, as in the reaction of the thianthrene and phenothiazine radical cations in neat pyridine or with pyridine in an anhydrous solvent. In this reaction the 1-pyridinium group is inserted on to the benzo ring (43), apparently via nucleophilic attack on di-cations 42, in turn resulting from oxidation of the initially formed radical cation adducts (Scheme 27). In the presence of moisture the sulfoxides are again formed [84]. 

Redox processes involving 178 have also been studied.Anodic oxidation of thianthrene has been eifected in a wide variety of solvents. Use of trifluoracetic acid gives stable solutions of 178 and, if perchloric acid is included, the solid perchlorate salt may be isolated on evaporation of the solvent after electrolysis. Dichloromethane at low temperatures has been used and, at the opposite extreme, fused aluminum chloride-sodium chloride mixtures. " Propylene carbonate permits the ready formation of 178, whereas the inclusion of water in solvent mixtures gives an electrochemical means of sulfoxidizing thianthrene. Reversible oxidation of 178 to thianthrenium dication may be brought about in customary solvents such as nitriles, nitro compounds, and dichloromethane if the solvent is treated with neutral alumina immediately before voltammetry addition of trifluoracetic anhydride to trifluoracetic acid equally ensures a water-free medium. The availability of anhydrous solvent systems which permit the reversible oxidation and reduction of 178 has enabled the determination of the equilibrium constants for the disproportionation of the radical and for its equilibria with other aromatic materials. ... 

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