Benzodithiole

DMTrT = 5 -<9-di-/ -methoxytritylthymidine mTHPT = 5 -0-(4-methoxytetrahydropyran-4-yl)thymidine BDTT = 5 -<9-(l,3-benzodithiol-2-yl)thymidine MMTrT = 5 -<9-mono-/ -methoxytritylthymidine THPT = 5 -tetrahydropyranylthymidine TBDT = 3 -<9-(l,3-benzodithiol-2-yl)thymidine... 

Tlie interest in the preparation and use of dithiolium salts in connection with the synthesis of TTF derivatives led to the development of a new uses of heteroaromatic cations in organic synthesis. Based on that, a new carbonyl olefination for the synthesis of numerous heterofulvalenes was developed (77S861). For example, 2-dimethoxyphosphinyl-l,3-benzodithiole was deprotonated with butyllithium in THF at -78°C and the resulting phosphonate carbanion reacted with 9-alkyl-acridones to give the dithia-azafulvalenes of type 45 (78BCJ2674) (Scheme 15). 

The 2-substituted 1,3-benzodithioles 57 are readily lithiated and react as acyl anions with various electrophiles, including alkyl halides, aldehydes, ketones. 

Benzopentathiepin (3, R1 =R2 = H) is produced in 54% yield from 1,2,3-benzothiadiazole and sulfur402 and in 97% yield from 1,3-benzodithiole-2-thione and sulfur in liquid ammonia in the presence of 1,3-dinitrobcnzcnc.403 These methods have also been used for the preparation of various substituted benzopentathiepins 3. 

Method BAOi A titanium autoclave of 50-mL capacity was charged with a l,3-benzodithiole-2-thione (0.5 mmol), sulfur (as S8) (0.128 g, 0.5 mmol) and NH3 (1) (30 mL). The autoclave was closed and the mixture was stirred at 20 C for 30 min. The resulting solution was added dropwise through a needle bulb to benzene (80 mL) containing 1,3-dinitrobenzene (0.084 g, 0.5 mmol) and the mixture was stirred at 20 C until all the NH3 had evaporated (ca. 2h). The resulting solution was evaporated and the residue was chromatographed (silica gel, CC]4/hexane) to give the yellow crystalline product. 

A variety of products has been obtained from benzopentathiepin and reactive methylene compounds in the presence of triethylamine or sodium ethoxide. Malononitrile and ethyl cy-anoacetate yield the benzodithiins 9, R = CN and C02Et, respectively, ethyl acetoacetate and acetylacetone give benzodithioles 10, R = C02Et and Ac, respectively, and ethyl 2-chloro-propanoate gives the benzotrithiin 11, accompanied by a small amount of the benzodithiole 12.410... 

Aliphatic and aromatic isothiocyanates and isoselenocyanates react with benzopentathiepin to give l,3-benzodithiol-2-imines 14.412... 

Over the years, many spiropyran structures have been prepared. The pyran component consists of benzopyran or naphthopyran and the heterocyclic part consists of indoline, benzothiazoline, benzoxazoline, benzoselen-azoline, phenanthridine, acridine, quinoline, benzopyran, naphthopyran, xanthene, benzodithiole, benzoxathiole, and saturated heterocyclic rings such as pyrolidine and thiazolidine. 

The charge transfer salt (BDNT)2[Ni(mnt)2] (BDNT = 4,9-bis(l,3-benzodithiol-2-ylidene)-4,9-dihydronaphtho[2,3-c]l,2,5-thiadiazole) also shows ferromagnetic interaction with /=3.4K, which was concluded to arise from the [Ni(mnt)2]- component on the basis of EPR evidence. In the absence of structural data, however, further understanding of this behavior could not be obtained. The anion was shown to be monoanionic, hence the valence of BDNT is +0.5.1051... 

Unexpectedly, upon reacting commercially available ethylene trithiocarbonate 111 with benzyne, the salt 103a was obtained as the major product along with a small amount of l,3-benzodithiole-2-thione 109a, as shown in Equation (31) <1996CC205> and <1996BCJ2349>. 

The thermal ring closure of AKl,3-benzodithiol-5-yl)aminomethylene-malonate (860) in Dowtherm A at 253-258°C led to a 7.3 1 mixture of 1,3-dithiolo[4,5-g]quinolinecarboxylate (861) and l,3-dithiolo[4,5-/]quinoli-necarboxylate (862) in 81% yield (86M1339). The cyclization of diethyl N-(3,4-dimethylthiophenyl)aminomethylenemalonate under similar conditions afforded only ethyl 6,7-dimethylthio-4-hydroxyquinoline-3-carbox-ylate. 

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