From Tellurium and Organo Alkali Metal Compounds

From Tellurium and Organo Alkali Metal Compounds 

The insertion of elemental tellurium into C — Li or C—Na bonds is a convenient method for the preparation of alkali metal tellurolates. Many organic lithium compounds are commercially available or can be prepared, for instance, by halogen-lithium or hydrogen-lithium exchange. The reactions of the organic lithium compounds with elemental tellurium are performed in inert organic solvents such as diethyl ether, tetrahydrofuran, tetrahydrofuran/hexane, or diethyl ether/benzene at temperatures (—196° to -1-20°) compatible with the stability of the organic lithium compound. The applicabiUty of this reaction for the synthesis of aliphatic, aromatic, and heteroaromatic lithium tellurolates is documented in Table 1 (p. 155). 

The preparation of an aryl lithium compound from an aryl halide and an alkyl lithium compound also produces an alkyl halide. The alkyl halide may react subsequently with the lithium arenetellurolate to yield aryl alkyl tellurium compounds. In these cases the tellurolate has only a transitory existence. 

Commercially available butyl lithium was frequently used to prepare aryl lithium compounds from aryl bromides. In these cases the aryl butyl tellurium compounds were the products isolated from the reaction mixtures. 

However, when t-butyl lithium was used to generate an aryl lithium compound from an aryl bromide, the /-butyl bromide formed did not react with the lithium arenetellurolate . 

---