From Diaryl Tellurium Dichlorides

Diaryl tellurium dicarboxylates were prepared in good yields from diaryl tellurium dichlorides and anion exchange resins such as Amberlite IR45 and Amberlite IR400 in their carboxylate form. The carboxylate resins were obtained by treating the resins in the OHe-form with carboxylic acids or the resins in the Cle-form with sodium carboxylates4. 

Dialkyl, alkyl aryl, and diaryl tellurium dichlorides were reduced by thiourea dioxide in a 2 molar aqueous solution of sodium hydroxide to the corresponding diorgano tellurium compounds4,5. The tellurium species actually reduced are the diorgano tellurium oxides or dihydroxides that are formed from the dichlorides in the basic medium. 

Because diaryl telluriums can be prepared from aromatic hydrocarbons and tellurium followed by reduction of the diaryl tellurium dichlorides, the overall reaction sequence converts arenes to biaryls. The formation of benzene from diphenyl tellurium and Raney nickel was also reported3. 

Arenediazonium chlorides react with elemental tellurium to form diaryl tellurium dichlorides in yields not exceeding 40%. The diazonium salts were prepared from aromatic amines and amyl nitrite14. 

Bis[3-methylphenyl] Tellurium Dichloride1,2 15 g (0.12 mol) of tellurium, 20 g of calcium carbonate, and 300 ml of acetone are added to a solution of 3-methylbenzenediazonium chloride [prepared from 20 g (0.19 mol) of 3-methylaniline and amyl nitrite] at 0°. When nitrogen evolution has ceased, the mixture is stirred at 20° for 30 min and under reflux for 1.5 h. The mixture is then filtered, the filtrate is concentrated on a water bath, and the residue is recrystallized from methanol/acetone yield 5.2 g (14%) m.p. 184". Examples of diaryl tellurium dichlorides prepared similarly1 are (yields not reported) ... 

Arenediazonium tetrafluoroborates were unreactive towards tellurium3 under conditions that had produced diaryl tellurium dichlorides from arenediazonium chlorides. However, addition of lithium chloride to a mixture of tellurium and 4-nitrobenzenediazonium tetrafluoroborate led to the formation of bis[4-nitrophenyl] tellurium dichloride in 33% yield2. 

Table 16 Diaryl Tellurium Dichlorides from Tellurium Tetrachloride and Aromatic Compounds...

Diaryl tellurium dichlorides can be obtained by condensation of aromatic hydrocarbons with tellurium tetrachloride. Refluxing solutions of the tellurium dichlorides in bis-[methoxyethyl] ether in the presence of Raney nickel2 3 or in acetic acid/sodium acetate in the presence of palladium(II) chloride4 produces biaryls in yields ranging from 10 to 91%. 

Diaryl tellurium dichlorides, obtainable from aromatic compounds and tellurium tetrachloride, react with excess bromine or iodine in refluxing DMF or acetonitrile in the presence of a metal fluoride to give aryl halides in low yields. The reactions with chlorinating agents are very sluggish. The reaction of bromine and bis[4-methoxyphenyl] tellurium dichloride formed 2,4-dibromomethoxybenzene in 76% yield. Reactions of these tellurium dichlorides with copper(I) cyanide in DMF produced aryl cyanides in yields of less than 8%3. 

Treatment of diaryl tellurium dichlorides, obtainable from tellurium tetrachloride and aromatic compounds, with carbon monoxide in the presence of palladium(II) chloride/lithium chloride gives arenecarboxylic acids. Biaryls are formed as by-products1,2. Similar products were obtained when the diaryl tellurium dichlorides were reacted with nickel tetracarbonyl3. 

When the alcohol from which the sodium alkoxide is derived cannot serve as the reaction medium, the diaryl tellurium dichloride and the alkoxide or phenoxide are refluxed in... 

Diaryl Tellurium Dicarboxylates4 5g of Amberlite IR45 resin in the OHe-form (theoretical exchange capacity 2 mequiv/ml) are placed in a 10 mm ID glass tube. A 4% ethanolic solution of the carboxylic acid in ethanol is slowly passed through the resin until the conversion to the carboxylate form is complete. The resin is washed with ethanol to remove excess carboxylic acid and dried in a stream of nitrogen. 1 mmol of the diaryl tellurium dichloride is dissolved in 20 ml of THF/ethanol (1/1, v/v) and this solution is slowly passed through the resin. The resin is rinsed with 50 ml of the solvent mixture, the combined effluents are evaporated in a rotary evaporator, and the crude dicarboxylates, obtained in 100% yield, arc recrystallized from benzene/petroleum ether. 

Dionium Diaryltetrahalotellurates(l V)1 2 mmol of the diaryl tellurium dichloride and 4 mmol of the onium halide are added to 30 ml of chloroform, the mixture is heated under reflux for 5 h, and then concentrated. Ethyl acetate is added to precipitate the product which is then recrystallized from dichloromethane/ethyl acetate (1/1, v/v) or acetonitrile/ethyl acetate (1/1, v/v) yield 80-100%. 

Equimolar amounts of diaryl tellurium dichlorides and sodium or silver trihaloacetates were stirred and refluxed for 3 h in benzene. The silver chloride was removed by filtration and the filtrate evaporated under reduced pressure. The residue was recrystallized from chloroform/petroleum ether (5 1) to give diorgano tellurium chloride trihaloacetates b... 

The disodium salts of dihydroxyimines reacted similarly with diaryl and alkyl aryl tellurium dichlorides in refluxing benzene3 5. The white, yellow, or brown products were obtained in yields from 60 to 70%. The compounds have sharp melting points and are stable towards atmospheric oxygen and moisture3. 

Biaryls can be synthesized in good yields by reduction (with Raney nickel) of diaryltellurium dichlorides. Thus, di(p-methoxyphenyl)tellurium dichloride, from anisole and TeCU, gives 4,4 -dimethoxy-l,l -biphenyl in 78— 90% yield. Diaryltellurium dichlorides may also be synthesized, in high yields, by reaction between TeCU and diaryl-mercury(ll) compounds. ... 

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