Telluronium Bromide

General procedure - with telluronium salt method A mixture of trimethylsilylprop-2-enyl(di-isobutyl)telluronium bromide (0.33 g, 0.75 mmol), cesium carbonate (0.25 g, 0.75 mmol), chalcone (0.5 mmol), and DME (5 mL) and water (5 mm ) was heated at 70°C for specific periods of time. When the reaction was complete (monitored by TLC), the resulting mixture was eluted with ethyl acetate through a short column of silica gel. Removal of the solvent and flash chromatography on silica gel gave the desired pure product, of purity >98% (GC). 

At this stage, however, addition takes place between the cydotelluio-pentane and alkylene dihalide, forming two complex telluronium bromides. 

Reaction of allyl diphenyl telluronium bromide with iodine bromide in chloroform solution yielded diphenyl tellurium dibromide on evaporation of the solvent2. 

Allyl 4-methoxyphenyl phenyl telluronium bromide and bromine produced 4-methoxy-phenyl phenyl tellurium dibromide2. 

From Allyl Diaryl Telluronium Bromide and Iodine... 

When allyl diphenyl telluronium bromide was treated with iodide in chloroform solution, diphenyl tellurium bromide iodide was isolated on evaporation of the solvent3. Similar reactions with iodine bromide produced only diaryl tellurium dibromides3. 

Stirring allyl diaryl telluronium bromide with cyanogen bromide in chloroform for 8 h at 20° yielded diaryl tellurium bromide cyanides3. 

Heating aluminum telluride and excess 1,4-dibromobutane at 125° produced 4-bromobutyl tetramethylene telluronium bromide and butane-1,4-diyl bis[tetramethylene telluronium] dibromide2. 

Tetramethylene Telluronium Bromides2 30 g (69 mmol) of aluminum telluride and 67 g (310 mmol) of 1,4-dibromobutane are placed in a 250 ml, round-bottom flask fitted with a reflux condenser and a stirrer. The stirred mixture is heated at 125° when the reaction becomes too vigorous the flask is cooled. When the reaction has subsided the mixture is heated for 2 h, then cooled to 20°. The semi-solid mass is extracted in sequence with carbon tetrachloride, acetone, ethanol, and water. The acetone and ethanol extracts are combined, evaporated, and the residue is recrystallized from ethanol to give white crystals of 4-bromobutyl tetramethylene telluronium bromide. 

Similarly prepared were the following allyl diorgano telluronium bromides ... 

The cleavage of Te-C (phenyl) bonds was observed in reactions between diphenyl tellurium dichloride and 2-phenylethyl magnesium bromide in a diethyl ether/benzene medium at room temperature. Tris[2-phenylethyl telluronium bromide (m.p. 127°) and chloride (m.p. 135°) were isolated in approximately 40% yield4. 

Biphenyldiyl 2-bromo-2 -biphenyl telluronium bromide (m.p. 264°, yield 79%) and the corresponding iodine compound (m.p. 265c, yield 63%) were similarly prepared2,3. Tetraphenyl tellurium transferred an anionic phenyl group to benzaldehydc and triphenyl boron yielding triphenyl telluronium salts4. 

Triphenyl Telluronium Tribromomercurate (H)6 Saturated ethanolic (or aqueous) solutions of triphenyl telluronium bromide and mercury(II) bromide are mixed, the mixture is filtered, and the solid is recrystallized from acetone m.p. 144°... 

Triphenyl Telluronium Phenylbromotrichlorotellurate(IV)8 25 ml of chloroform, 1.31 g (3 mmol) of triphenyl telluronium bromide, and 0.93 g (3 mmol) phenyl tellurium trichloride are placed in a 100 ml flask fitted with a reflux condenser. The mixture is heated under reflux for 4 h, the solvent is evaporated, and the residue is recrystallized from dichloromethane/ethyl acetate yield 1.91 g (85%) m.p. 194°. 

Triphenyl Telluronium 4-Edioxyphenyltetrachlorotellurate(IV)1 0.36 g(l mmol) of4-ethoxyphenyl tellurium trichloride are dissolved in 6 molar hydrochloric acid and a solution of 0.44 g (1 mmol) of triphenyl telluronium bromide in 20 ml of water is added dropwise with stirring. The precipitate is filtered off yield 0.80 g (100%) m.p. 143°. 

Bis[triphenyl telluroniumJ Hexabromotellurate(IV)1 A mixture of 50 ml of chloroform, 2.2 g (5 mmol) of tellurium tetrabromide, and 4.4 g (10 mmol) of triphenyl telluronium bromide in a 250 ml flask fitted with a magnetic stirrer and a reflux condenser is heated under reflux and stirring for 6 h. The precipitate is filtered off yield 6.6 g (100%) m.p. 228° (from dimethylformamide/ethyi acetate). 

Examples of telluronium bromides prepared in this manner are ... 

Aqueous or methanolic solutions of triorgano telluronium bromides that are not too dilute precipitate triorgano telluronium iodides when mixed with solutions of potassium iodide5,6 (Vol. IX, p. 1080). 

Carboxymethyl Diphenyl Telluronium Hydroxide1 5.0 g (12 mmol) of carboxymethyl diphenyl telluronium bromide and 2.0 g (8.6 mmol) of silver oxide in 45 ml of water are shaken for 4 days. The mixture is filtered, the filtrate is concentrated under vacuum at 20°, and the crystals are collected m.p. 118°. 

Triphenyl Telluronium Triboranate-82 1.00 g (2.3 mmol) of triphenyl telluronium bromide are dissolved in 100 ml of water and 0.26 g (2.2 mmol) of tetramethyl ammonium triboranate-8 are dissolved in 50 ml of water. The two solutions are cooled to 0 and mixed. The precipitate is filtered off, washed under nitrogen with diethyl ether, and dried in a stream of nitrogen yield 0.83 g (95%) m.p. 57° (dec ). 

Trimethyl Telluronium Tetrabromoborate1 1.69 g (6.7 mmol) of trimethyl telluronium bromide and lSg (60 mmol) of boron tribromide are mixed in a vacuum line trap, the mixture is stirred magnetically at 20° for 8 h, and excess boron tribromide is then removed to leave the colorless product m.p. 215 (dec ). 

Alkoxycarbonylmethyl diphenyl telluronium bromides shaken with an aqueous suspension of silver oxide for 3 days produced carboxymethyl diphenyl telluronium hydroxides. 

Diorgano alkyl telluronium bromides were converted to diorgano alkylidene telluriums on treatment with potassium tert.-butoxide2 (see p. 718). 

Dibutyl methoxycarbonylmethyl, dibutyl cyanomethyl, and dibutyl 2-oxo-2-phenylethyl telluronium bromides react with benzaldehydes in refluxing tetrahydrofuran to form ethene derivatives and dibutyl tellurium oxide1,2. 

Dialkyl allyl telluronium bromides and dibutyl ethoxycarbonylmethyl (cyanomethyl, benzoylmethyl) telluronium bromide generated dialkyl alkylidene telluriums on treatment with potassium ferf-butoxide in tetrahydrofuran at low temperatures (s. p.837). The tellurium ylides were not isolated but were trapped with aldehydes and ketones4-6. 

Diisobutyl 2-Propen-l,l-ylideoe TeBurium4 0.87 g (2.4 mmol) of allyl diisobutyl telluronium bromide and 0.27 g (2.4 mmol) of potassium fert-butoxide are placed in a nitrogen-filled vessel. The vessel and 4 ml of dry tetrahydrofuran are cooled to — 78°. With stirring, the tetrahydrofuran is added dropwise to the mixture, stirring is continued for a few minutes, and then a solution of 0.216 g (2 mmol) of bcnzaldehydc in 2 ml of tetrahydrofuran is added dropwise to the ylide. The mixture is allowed to warm slowly to 20°. Work up and column chromatography on silica gel gives diisobutyl telluride and 2-phenyl-3-vinyIoxirane yield 82%. 

Similar reactions with dibutyl cyanomethyl telluronium bromide and dibutyl benzoylmeth-yl telluronium bromide gave the expected dibutyl alkylidene telluriums however, their reactions with benzaldehydes in tetrahydrofuran yielded cyanoethenes and conjugated enones but no epoxides1. 

Ethoxyphenyl Tetramethylene Telluronium Bromide A solution of 3.08 g (6.2 mmol) of bis[4-ethoxyphenyl] ditellurium in a mixture of 2.5 ml of benzene and 7.5 ml of ethanol is heated under reflux. 0.04 g (10 mmol) of sodium borohydride dissolved in 8.5 ml of 1 molar aqueous sodium hydroxide solution followed by 0.22 g (1 mmol) of 1,4-dibromobutane dissolved in 5 ml of benzene are added dropwise to the refluxing solution. The warm mixture is stirred for 30 min, filtered, the solid is washed with diethyl ether, and dried under vacuum yield 0.30 g (80%) m.p. 280° (from acetonitrile). 

Allyl Diphenyl Telluronium Bromide 1.13 g (4.0 mmol) of diphenyl tellurium are mixed with 7.0 g (5 ml, 58 mmol) of allyl bromide and kept at 70° for 40 h. The mixture is then cooled to 20° and kept at that temperature for 12 h. Diethyl ether is added to the mixture to precipitate the product. The crystals are allowed to stand in contact with the diethyl ether for 24 h, then filtered, and dried yield 1.5 g (94%) m.p. 130". 

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