Synthesis of Thianthrenes

In the first edition of Comprehensive Heterocyclic Chemistry (CHEC-I), published early in 1984, Cook exhaustively reviewed the six-membered rings with more than one oxygen or sulfur atom <84CHEC-1(3)943>. In 1990, Joule in Advances in Heterocyclic Chemistry provided a very comprehensive discussion of the structure, physical properties, reactivity, and synthesis of thianthrenes <90AHC(48)301>. 

Dithians. - A new synthesis of thianthrene and its symmetrically substituted derivatives has been described in which a 1,23-benzothiadiazole (262) is heated in benzene that contains di-t-butyl peroxidel-(3-Chloroethyl-... 

Initial methods for the synthesis of thianthrene were based on the reaction of benzene with sulfur and its dichloride in the presence of aluminum chloride. ... 

Overall goals of our research in this area include synthesis of thianthrene di-, tri- and tetracarboxylic acid derivatives (10,11,12,13 Figure 7) starting with 3,4-dichlorobenzoic acid and 4,5-dichlorophthalic acid evaluation of their use in formation of thianthrene-containing polyimides, aramids, and polybenzoxazoles and... 

The earliest reported reference describing the synthesis of phenylene sulfide stmctures is that of Friedel and Crafts in 1888 (6). The electrophilic reactions studied were based on reactions of benzene and various sulfur sources. These electrophilic substitution reactions were characterized by low yields (50—80%) of rather poorly characterized products by the standards of 1990s. Products contained many by-products, such as thianthrene. Results of self-condensation of thiophenol, catalyzed by aluminum chloride and sulfuric acid (7), were analogous to those of Friedel and Crafts. 

SrnI processes have been shown to be relevant to the synthesis of simple thianthrenes which is done by irradiating the disodium salt of 4-methylbenzene-1,2-dithiol in the presence of 1,2-bromochlorobenzene (55%) or 1,2-di-iodobenzene (64%). More complex, fused thianthrenes result from l-bromo-2-iodonaphthalene (24%, 2 isomeric products) and 2,3-dichloroquinoxaline (100%). These clearly hold considerable promise for the controlled construction of unsymmetrical thianthrenes (87JOC1089). 

A Newman-Kwart rearrangement of the O-thiocarbamoy I derivative of a thiacalix[4]arene results in the synthesis of thiacalix[2]thianthrenes 69. The two thianthrene units are linked by two sulfur bridges producing a basket-shaped molecule <07TL5401>. Treatment with... 

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]. 

The direct synthesis of fully functionalized sugars possessing amino or hydroxyl functions at C-2 has also been studied. Thus, activation of glycals by thianthrene-5-oxide 287 and Tf20, followed by treatment with an amide nucleophile and a glycosyl acceptor, led directly to various 2-acylamido glycosides 288 [610,611] (Scheme 4.59). 

J. B. Edson and D. M. Knauss. Thianthrene as an activating group for the synthesis of poly(aryl ether thianthrene)s by nucleophilic aromatic substitution. J. Polym. Set, Part A Polym. Chem., 42(24) 6353-6363, December 2004. 

R.A. Johnnson, L.J. Mathis, Synthesis and characterization of thianthrene-containing poly(benzoxazole)s, J. Polym. Sci. Part A Polym. Chem. 33 (11) (1995) 1901-1906. 

The synthesis of 5-arylthianthrenium salts, 8, [CRI 02a, CRI 04] can be carried out by the condensation of thianthrene-S-oxide with various aromatic compounds bearing electron-donating substituents, R, as depicted in equation [2.1], A mixture of methanesulfonic acid and phosphorous pentoxide serves as an acid catalyst and dehydrating agent for this reaction. Replacement of the methanesulfonate anion by a metathetical reaction with NaMtXn affords the desired active photoinitiator, 8. Depending on the specific R substituent, 5-arylthianthrenium photoinitiators have UV absorption maxima in the range of 300-400 nm. 

Heterocyclic Synthesis. The reaction of 1,2,3-benzothiadia-zole with PhSH/AIBN in refluxing EtOAc provides a mixture of products including dibenzo[c,e]-o-dithiin (1), thianthrene (2), and 2-(phenylthio)diphenyl disulfide (3). ... 

Synthesis and Properties.—The two most general methods for preparing sulphonium ylides continue to be a-deprotonation of a sulphonium salt and the reaction of a sulphide (or disulphide with a carbene. A new development involves the reaction of the thianthrene or phenoxathiin cation radical with a dicarbonyl compound, e.g. ethyl benzoylacetate, to give (4). An infrequently used but useful route to sulphonium ylides involves reaction of sulphides e.g. dithia[3,3]cyclophanes with benzyne. A detailed description of a preparation of the sulphonium salt precursor to Trost s diphenylsulphonium cyclopropylide has appeared. The selectivity of ylide formation in the reaction of cyclic and acyclic sulphides with carbenes has been examined and compared with the much... 

The first thianthrene dication (32) has been isolated. Work on the thianthrene cation radical (33) continues. Its reaction with aliphatic amines yielded the sulphimides (34 X = NR) phenols and aromatic amines were attacked in the pflra-position to afford (34 X = / -HOCeH4 or p-R2NC H4), and enolizable ketones yielded the j8-keto-sulphonium salts (34 X = CHR COR ). The latter compounds reacted with nucleophiles Y to give the a-substituted ketones YCHR COR, and might prove to be useful intermediates for their synthesis. Reinvestigation of the kinetics of the reaction of (33) with phenol and with anisole has provided evidence which appears to disprove the disproportionation mechanism postulated earlier for these reactions. 

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