Telluraxanthene

When refluxed in diethyl ether, tellurium and bis[2-lithiophenyl]methane produced telluraxanthene.  

Telluraxanthene 3.33 g (1.02 mmol) of bis[2-bromophenyl]methane are disolved in 300 m/] of absolute diethyl ether and, under dry nitrogen, 22m/j (36.1 mmol) of a 15% solution of butyl lithium in hexane are added dropwise. The mixture is heated under reflux for 0.5 h, cooled to 20°, and 1.8 g (14.1 mmol) of finely powdered tellurium are added. The resultant mixture is heated under reflux for 2 h and then poured into ice/water. The mixture is extracted with chloroform, the extract is filtered, and the solvent is evaporated in a rotary evaporator at 20° under aspirator vacuum. The residue is recrystallized from diethyl ether/petroleum ether after addition of activated charcoal yield 1.42 g (47%) m.p. 151°. 

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The second method employed for the synthesis of telluraxanthene is similar to that widely used for the preparation of various tricyclic heterocycles containing one or two heteroatoms. It is based on the interaction of 2,2 -dilithiodiphenylmethane with powdered tellurium, by which reaction telluraxanthene 82 has been prepared in 50% yield [81JOM(205)167]. The reaction apparently proceeds through the intermediate bis(telluro-phenolate) 86 which is oxidized to the heterocyclic ditelluride 87. The latter compound eliminates tellurium from its stericaily strained seven-membered ring and converts to telluraxanthene. This mechanistic scheme seems to be corroborated by the observation that the treatment of lithi-oarenes ArLi usually ends in the formation of diarylditellurides Ar2Te2 (74MI1 83MI2). 

Although the first method is a four-step sequence of reactions and the second one is a one-step reaction, the yields of telluraxanthene are... 

Substituted telluraxanthenes have scarcely been studied. 9-(p-Tolyl)-telluraxanthene has been prepared in high yield by the reduction of 9-(p-tolyl)telluraxanthenol 91 with LiAlH4 in the presence of anhydrous A1C13 and also by the reduction of 9-( p-toly 1)-10-telluroniaanthracene 92 with LiAlH4 (81KGS343). 

Treatment of telluraxanthene with phenyllithium in benzene gives 9-lithiotelluraxanthene in 60% yield (80KGS1342). Reaction with trityl perchlorate converts 82 into 10-telluroniaanthracene perchlorate (Section... 

II,H,1). The methylene group of telluraxanthene can be easily oxidized to a carbonyl group, telluraxanthone being the product. 

In fact, the only known method of synthesis of telluraxanthone 94 is that based on the oxidation of telluraxanthene (80KGS1342) or 10,10-dichlorotelluraxanthene [80KGS1342 81JOM(205)167] with potassium dichromate (80KGS1342) or chromic anhydride [81JOM(205)167] in acetic... 

A less common approach to the tellurachromylium and telluraxanthyl-ium cations is based on dehydrogenation of 2//-tellurachromene 53 (86KGS1570) and telluraxanthenes 82 (81KGS343) with trityl perchlorate. 

Telluraxanthene Te.Te-dichloride is formed when 2-(phcnylmethyl)-phenyl tellurium trichloride is heated in 1,2-dichlorobenzene at 70° in the presence of aluminum trichloride1,2. 

Telluraxanthene Te,7e-Dichloride2 12 g (30 mmol) of 2-(phenyhnethyl)-phcnyl tellurium trichloride are suspended in 80 m/] of freshly distilled 1,2-dichlorobenzene. Under a dry atmosphere 4.0 g (30 mmol) of anhydrous aluminum trichloride is added in portions to the stirred suspension. The mixture is then heated with stirring at 65-70° for 5 h, cooled, and poured into 300 ml] of chloroform. 300 ml] of 3 molar hydrochloric acid are carefully added, the mixture is stirred for 5 min, and filtered. The organic layer is separated, dried with anhydrous sodium sulfate, filtered, and the solvent is distilled until crystals begin to form. The solution is then cooled to 20°, and the slightly-ycllow colored crystals are filtered off and recrystallized from chlorobenzene yield 8.76 g (80%) m.p. 250 270°. 

The telluraxanthene dichloride was reduced to telluraxanthene with potassium disulfite2. 

Telluraxanthene2 4.0 g (11 mmol) of telluraxanthene dichloride are suspended in 30 ml of water, 10 g (45 mmol) of finely ground potassium disulfite are added in small portions over 30 min to the suspension held at 40-50°. The mixture is then cooled, filtered, and the solid on the filter is washed with a small amount of cold water, dried, and recrystallized from petroleum ether yield 3.0 g (93%) m.p. 151°. 

With Replacement of a Methylene Hydrogen Atom in Telluraxanthene... 

Telluraxanthene was converted to 9-lithiotelluraxanthene in a reaction with phenyl lithium. The lithiotelluraxanthene and carbon dioxide reacted to produced 9-carboxytelluraxanthene2. 

Carboxytelluraxanthene2 A solution of phenyl lithium is prepared from 3.5 g (22 mmol) of bromobenzene and 0.3 g (44 mmol) of lithium in 50 ml of absolute diethyl ether. This solution is added to a stirred solution of 5.88 g (20 mmol) of telluraxanthene in 50 ml of absolute benzene, the mixture is stirred at 20° for 1 h, and then heated under reflux for 1 h. The resultant dark red solution of 9-lithiotelluraxanthene is poured onto dry ice, the carbon dioxide is allowed to evaporate, and the solution is shaken with aqueous sodium hydroxide solution. The aqueous layer is separated, extracted several times with benzene, and acidified with concentrated hydrochloric acid. The precipitate is filtered, washed with ice/water, and dried yield 4.4 g (65%) m.p. 209° (dec., from ethanol). 

Lithium aluminum hydride reduced 9-hydroxy-9-(4-methylphenyl)-telluraxanthene to 9-(4-methy lpheny l)-telluraxanthene1. 

MethylphenyI)-teUuraxanthene1 0.5 g (13 mmol) of lithium aluminum hydride and 3.0 g (23 mmol) of aluminum trichloride are suspended in 50 ml of absolute diethyl ether. To the stirred suspension at 20 are added 1.60g (4 mmol) of 9-hydroxy-9-(4-methylphenyl)-telluraxanthene and the mixture is heated under reflux for 1 h. After cooling, it is diluted by slow addition of 50 ml of diethyl ether, the resultant solution is poured into 100 ml of 20% aqueous sulfuric acid, the mixture is filtered, and the filtrate separated into two layers. The aqueous layer is washed with two 50 ml portions of diethyl ether. The organic phases are combined, dried with anhydrous sodium sulfate, filtered, and the filtrate is evaporated yield 1.23 g (80%) m.p. 1G3°. 

Concentrated hydrofluoric and trifluoroacetic acid cleave 7e-(4,4-dimethyl-2,6-dioxo-cyclohexylidene)-telluraxanthene forming telluraxanthene difluoride and bis[trifluoro-acetate]3, respectively. 

Telluraxanthene Te, TV-Difluoride1 1 ml of concentrated hydrofluoric acid is added to a hot solution of 2.0 g (4.6 mmol) of 7c-(4,4-dimethyl-2,6-dioxocyclohexylidene)-telluraxanthene in 10 ml of ethanol. The solvent is evaporated, the residue is washed with benzene, and the solid is dried and recrystallized from chlorobenzene yield 1.51 g (98%) m.p. > 260° (dec). 

Mercury(II) halide adducts of telluraxanthene precipitated when solutions of the two components in ethanol/benzene were combined1. 

Telluraxanthene/Mercury(II) Chloride Adduct1 A solution of 1 -36 g (5 mmol) of mercury(II) chloride in 10 m/ of ethanol is mixed with a solution of 1.47 g (5 mmol) of telluraxanthene in 50 ml of benzene, the mixture is stirred and heated under reflux for 30 min, cooled, and the yellow precipitate is collected by filtration yield 2.38 g (84%) m.p. 205 (from toluene). 

Telluraxanthene did not form an adduct with tetracyanoquinodimethane in refluxing acetonitrile2. 

Telluraxanthene dihalides were also obtained from telluraxanthene and copper(II) chloride or copper(II) bromide in aqueous acetone3. 

Telluraxanthene Te,Te-Dichloridei 1.47 g (5 mmol) of telluraxanthene are dissolved in 50 ml of acetone, a solution of 1.40 g (11 mmol) of copper(II) chloride is added dropwise, and the resultant mixture is heated under reflux for 30 min. The mixture is then filtered to remove copper(I) chloride, the filtrate is poured into water, the mixture is filtered, and the solid is recrystallized from chlorobenzene yield 1.20 g (76%) m.p. 250-270°. 

A telluronium salt could not be obtained from telluraxanthene and methyl iodide. However, the telluronium perchlorate was formed in high yields when silver perchlorate was added to the reaction mixture3. 

MethylteIluraxanthylium Perchlorate1 A solution of 2.08 g (10 mmol) of silver perchlorate in 50 ml of acetonitrile is added dropwise to a solution containing 2.94 g (10 mmol) of telluraxanthene and 11.4 g (5 ml 80 mmol) of methyl iodide. The mixture is stirred and heated under reflux for 30 min, cooled, the precipitated silver iodide is removed by filtration, and the filtrate is evaporated to leave colorless crystals that melt and explode at 183°. 

Telluraxanthene 7i ,7e-dichloride condensed with 5,5-dimethyl-l,3-dioxocyclohexane to form an ylide1. 

Dimethyl-2,6-dioxocyclohexylidene)-teIluraxanthene1 7.28 g (20 mmol) of telluraxanthene Te,Te-dichloride and 2.8 g (20 mmol) of 5,5-dimethyl-l,3-dioxocyclohexane are dissolved in 60 ml of benzene, the solution is stirred at 60-70°, and 7 ml (5.1 g 50 mmol) of triethylamine are added. The solution is heated and stirred for a further 20 min, filtered hot, and the solvent is distilled from the filtrate. The colorless crystals are recrystallized from benzene/pctrolcum ether yield 8.6 g (100%) m.p. 156 ... 

Azido-9-(4-methylphenyl)telluraxanthene in refluxing xylene formed 9-(4-methyl-phenylimino)telluraxanthene and 11-(4-methylphenyl)dibenzotelluruzepine2. 

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