Butyl vinyl telluride

In the case of symmetrical divinyl tellurides, the displacement of both vinyl groups is achieved by employing 2 equiv of n-butyllithium. Aryl vinyl tellurides give a mixture of products, since both Ar-Te and vinyl-Te bonds are transmetallated on reaction with n-BuLi, leading to vinyl- and aryllithiums. The butyl vinyl tellurides give only the desired vinyl-lithiums. The reactions are stereospecific with retention of the C=C bond geometry. °... 

Lithium-tellurium exchange generation of vinyllithium (typical procedure). Method A. To a solution of butyl vinyl telluride (0.211 g, 1 mmol) in THF (4 mL) at -78°C under N2 is added dropwise a solution of n-BuLi (1.5 M in hexane, 0.67 mL, 1 mmol). After stirring for 40 min at -78°C, benzaldehyde (0.016 g, 1 mmol) is added. The mixture is allowed to react at room temperature for 30 min, diluted with EtOAc (40 mL) and washed with brine. 

A preliminary investigation directed to determine the influence of the substituents in both the telluride and the starting cuprate, employing cyclohexenone as substrate, showed that phenylvinyl tellurides are not appropriate as the source of the vinyl copper reagent, since both the vinyl and phenyl groups are transmetallated and add to the enone. This result could be anticipated since both the formed carbanions are sp hybridized. Otherwise, butyl vinyl tellurides undergo exclusive Te/vinyl transmetallation followed by the desired vinyl transfer. 

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. 

Alkyl vinyl tellurides (general procedure) A solution of the divinylic ditelluride (1.0 mmol) in THF (6 mL) is added dropwise, at room temperature under Nj, to AILiH4 (0.09 g, 2.5 mmol) in THF (3 mL). The dark red colour of the ditelluride disappears. The resulting mixture is treated with butyl bromide (0.3 g, 2.2 mmol) and stirred for 15 min. Then H2O (0.5 mL), 10% aqueous NaOH (0.5 mL) and HjO (0.5 mL) are added in sequence. The product is extracted with ether (3x10 mL). The extract is washed with brine, dried (MgS04) and evaporated, giving the product as a yellow oil. 

The reaction of enol phosphates 84 with lithium -butyl tellurolate 85a, generated by reaction of -butyllithium with elemental tellurium, occurs rapidly to give the corresponding vinylic tellurides 86 (Scheme 51). Mixtures of (Z)- and ( )-enol phosphates afford the (Z)-vinylic telluride as the only product. ... 

Phenylacetylene and sodium telluride combine to produce bis[(Z)-2-phenylethenyl] tellurium3, while phenylacetylene and sodium butanetellurolate3 or sodium benzenetel-lurolate4 yields organo (Z)-2-phenylethenyl telluriums. These vinyl telluriums are cleaved by butyl lithium in tetrahydrofuran at -78° to (Z)-2-phcnylcthenyl lithiums. 

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