277-1,3-Ditellurole

The easily accessible ethynyl tellurolates were reacted with chloroiodomethane to give ethynyl chloromethyl tellurium, which, in turn, combined with an alkali metal telluride to form (ethynyltelluro)methanetellurolates. These compounds cyclized through intramolecular addition of the tellurolate to the C —C triple bond to 277-1,3-ditelluroles ". ... 

Ditellurole (122) differs from the compounds described in the previous two sections due to its small ring size, combined with the presence of two sp -hybridized carbons (Fig. 45). As a result, formation of the intramolecular dimer radical cation... 

H-l,3-ditellurole. Under an atmosphere of argon, 0.23 g (2.4 mmol) of trimethylsily-lacetylene are dissolved in 5 mL dry tetrahydrofuran. The solution is cooled to -70°C. n-Butyl lithium (1.0 mL, 2.4 M, 24 mmol) is dropped into the stirred solution. Then 0.20 g (2.0 mmol) of tellurium powder is added. The mixture is warmed to 20°C and kept at this temperature for 2 h. To this mixture, cooled again to -70°C, is added a solution of 0.35 g (2.0 mmol) of chloroiodomethane in 1 mL of tetrahydrofuran. The mixture is stirred for 15 min and then quenched with 50 mL water. The product is extracted with three 15 mL portions of dichloromethane. The combined extracts are washed with brine, dried with anhydrous sodium sulphate and filtered. The filtrate is concentrated to give trimethylsilylethynyl chloromethyl tellurium as a pale-yellow oil. Tellurium powder (0.125 g, 1.0 mmol) is added to 2 mL of a 1 M solution (2.0 mmol) of lithium triethylborohydride in ethanol. The mixture is stirred at 20°C for 2 h under an atmosphere of argon. Then 2 mL of 1 M sodinm ethoxide in ethanol are added followed by 0.27 g (1.0 mmol) of trimethylsilylethynyl chloromethyl tellurium dissolved in 2 mL dimethylformamide. The mixture is stirred for 15 h at 20°C, then diluted with 25 mL water and extracted with three 15 mL portions of dichloromethane. The combined extracts are dried with anhydrons sodinm snlphate, fdtered and the filtrate concentrated. The residue is chromatographed on silica gel with hexane/dichloromethane (1 1) as mobile phase. The fractions containing the prodnct are concentrated and recrystallized from methanol 65% yield, m.p. 85°C. 

Bis[dimethylthienol]l,4,6,8-tetratellurafulvalene. 3,4-Dibromo-2,5 dimethylthiophene in tetrahydrofuran is treated at -78°C with 2 equiv of ferf-butyllithium. After 2 h, 1 equiv of tellurium powder is added. The mixture is slowly warmed to 0°C and kept at 0°C until all the tellurium has dissolved. The mixture is cooled again to -78°C, treated with tert-butyllithium and then with tellurium at 0°C. The ditellurolate solution is cooled to -78°C, mixed with 0.5 equiv of tetrachloroethene, stirred for 18 h and allowed to warm to 20°C. The brown solid is isolated by filtration and extracted with carbon disulphide. The extract is evaporated and the residue recrystallized from 1,1,2-trichloroethane to give bronze-coloured crystals. Yield 75% m.p. 295-298°C. 

Synthesis of compound A.A solution of 1,3-dibromopropane (10.1 g, 0.05 mol) in benzene (100 mL) was added to a solution of sodium telluride (NajTe 17.4 g, 0.1 mol) in ethanol (700 mL). After 3 h sodium borohydride (3.8 g, 0.1 mol) was further added to the mixture to produce sodium propane-1,3-ditellurolate, and then to the mixture was added a solution of the dibromopropane (10.1 g, 0.05 mol) in benzene (100 mL). The whole mixtnre was stirred at room temperature for 2 h. After usual work-up, the crude products were purified by silica gel column chromatography (eluent n-hexane/benzene) to afford compound A, which was further purified by preparative liquid chromatography. 

No halogenation was reported for 1,3- and 1,2-ditelluroles (91CHE235). A variety of nucleophilic substitution reactions with halides took place with 1,2-oxatelluroylium chlorides (101) (83JA875). 

Finally, a supramolecular three-dimensional network formed through - - secondary bonds has been described for the related tellurium compound (TMTTeN)2[Au(CN)2] (TMTTeN = (2,3,6,7-tetramethylnaphtho[l,8-cd 4,5-c d ]bis [l,2]ditellurole), a salt which is a quasi-three-dimensional conductor [76]. The donor molecules are stacked along the c-axis and take the same orientation with a short interplanar distance of about 3.4 A and a large slip distance of approximately 4 A. There are several intermolecular - - contacts, and a three-dimensional network through tellurium atoms is developed between the intracolumns and intercolumns. 

The first representative of the 1,2-ditelluroles, 3,4,5,6,7,8-hexachloro-naphtho[l,8-ct/] 1,2-ditellurole 37, was obtained in low yield by heating octachloronaphthalene with elemental tellurium at 350°C (73USP3769276) by analogy with the method developed for the synthesis of congeneric 1,2-dithiole and 1,2-diselenole derivatives (72T963). 

The same procedure was applied to the synthesis of 5,6-dihydroacenaph-tho[5,6-a/][l,2]ditellurole and diselenole 39 (88BCJ2013). 

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