Reactivity and synthetic applications of vinylic tellurides

Tellurium-lithium exchanges in the mono- and bis-telluroderivatives are a suitable route for the preparation of mono- and disubstituted ferrocenes.  

The formed vinylic cuprates readily perform conjugate addition to a,)3-unsaturated carbonyl compounds giving 8-vinyl-substituted ketones. 

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. 

2-Thienyl vinyl tellurides are valuable reagents for the transfer of the vinyl group. By treatment with Bu2Cu(CN)Li2 they are converted in a single step into the mixed cuprate 

The conjugate addition of higher-order (Z)-vinylic cyanocuprates, to enones,has been submitted to further useful modifications. Thus it was shown that the serious drawback of this methodology, which is the inertness of hindered enones to the mentioned reagents when THF is used as solvent, can be overcome by the addition of BFj etherate to the reaction mixture, or simply by performing the reaction in ether in the presence or absence of 

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