Thioxanthone 10,10-dioxides

Thioxanthone dioxide itself has been prepared directly from benzophenone by a double electrophilic substitution reaction with chlorosulfonic acid (Equation 190) <1995JCX321>. 

The first came from a continuing investigation of alternative tricyclic systems as carriers of the carboxylic acid function and the finding that compounds (5) in which X or Y equals sulphone, for example, had high activity. One of these, the thioxanthone dioxide BW 437C, had a higher ratio of oral to intravenous activity than we had observed before. 

Table 3 presents the hyperfme splitting constants of some sulfur-containing aromatic radical anions. The series studied included the monoxides and dioxides of dibenzothio-phene 1, thioxanthene 2, thioxanthone 3, dibenzo[b,/] thiepin 4 and dithienothiophene dioxide 5. 

Thioxanthone S-oxidec Thioxanthone S,S-dioxidec Dibenz[h,/]thiepin Dibenz[h,/]thiepin S-oxide Dibenz[6,/]thiepin S, S-dioxide Dithienothiophene 7,7-dioxide... 

Thioxanthone 9,9-dioxide is readily prepared by oxidation of the sulfide with peroxide. On treatment with methoxide it ring opens to generate a sulfinic acid (equation 62) (77SC33). 

An X-ray study of thioxanthone 10,10-dioxide (Figure 12) has established that the molecule is almost planar with a dihedral (fold) angle of 177°. The C-S-C bond angle of 105.2° is significant and the S-C bond lengths are comparable with those in thioxanthene and thioxanthone <1995JCX321>. 

The same metallation methodology features in a synthesis of 1-dimethylaminothioxanthone 10,10-dioxide. A key step is the introduction of a 6-phenylsulfonyl group into 2-dimethylamino-A iV-diethylaminobenzamide by directed metallation (Scheme 208) <2002JOC3585>. Other substituted thioxanthone 1,1-dioxides have been accessed by the directed metallation of diarylsulfone 2-carboxamides (Equation 188) <1994JOC6508>, a neat variant on the standard route to xanthones by the cyclization of benzoic acids. 

Excess 1 M diborane in tetrahydrofuran added during 0.5 hr. to thioxanthone 5,5-dioxide oxime acetate, and allowed to stand 12 hrs. at room temp. 10-amino-thioxanthene 5,5-dioxide. Y 69%. F. e. s. P. Catsoulacos, J. Heterocyclic Chem. 4,645 (1967). 

Hydroxybenzophenone-2-sulfinic acids from thioxanthone 10,10-dioxides... 

Important Initiators and accelerators unsaturations, aromatic carbonyl compounds (deoxyanisoin, dibenzocycloheptadienone, flavone, 4-methoxybenzophe-none, 10-thioxanthone), hydrogen bound to tertiary carbon at branching points, aromatic amines, groups formed on oxidation (hydroperoxides, carbonyi, carboxyi, hydroxyi) substituted benzophenones, compiexes with ground-state oxygen, quinones (anthraquinone, 2-chioroanthraquinone, 2-tert-butyi-athraquinone, 1-methoxyanthraquinone, 2-ethyianthraquinone, 2-methyianthraquinone), transition metai compounds (Ni < Zn < Fe < Co), ferrocene derivatives, titanium dioxide (anatase), ferric stearate, poiynuciear aromatic compounds (anthracene, phenanthrene, pyrene, naphthaiene ... 

The action of alkalis on a series of thioxanthone 10,10-dioxides has been investigated the products include xanthones and the hydroxybenzo-phenone-sulphonic acids from which they are derived. ... 

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