From vinylic tellurolate anions and alkyl halides

4 From vinylic tellurolate anions and alkyl halides 

This reaction is an application of the general method for the preparation of unsymme-trical tellurides (see Section 3.1.3). 

Vinylic tellurides (generalprocedure) Elemental Te (0.6 g, 5.0 mmol) is added to a solution of the vinylic magnesium bromide (5.5 mmol) in THE (10 mL) under reflux and N2 atmosphere, and the reflux maintained for 20 min. The mixture is allowed to reach room temperature and then treated with n-butyl bromide (0.7 g, 5.0 mmol). After stirring for 10 min, the reaction mixture is cooled at 0°C, treated dropwise with saturated aqueous NH4CI, extracted with ether, dried (MgS04) and then evaporated. Kiigelrohr distillation of the residue under vacuum gives the vinyl alkyl tellurides as yellow liquids. 

By treating the vinylic magnesium tellurolates with air while stirring, instead of with alkyl bromides, divinylic ditellurides are formed.  

Divinylic ditellurides (generalprocedure) Elemental Te (12.7 g, 100 mmol) is added at once to a stirred solution of the vinylic magnesium bromide (0.11 mol) in THE (150 mL) under N2. The mixture is refluxed for 30 min with stirring, allowed to reach room temperature, then stirred for 1 h in the presence of air (by opening the apparatus). Deposition of some Te is observed during the oxidation process. The mixture is treated with brine. 

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