Generation of allyl- and benzyllithiums from the corresponding halides by the aid of lithium-tellurium exchange reactions

Article abstract of DOI:10.1016/0022-328X(94)80107-X

A variety of allyl- and benzyllithiums were prepared by lithium-tellurium exchange reactions of allylic and benzylic tellurides generated in situ from the corresponding halides.The produced organolithiums were trapped successfully with electrophiles such as aldehydes, ketones, and trimethylchlorosilane.Benzyllithiums having an alkyl, alkoxy,fluoro, chloro, or cyano substituent(s) on their aromatic ring were generated efficiently in THF.Benzylic tellurides bearing a bromo or iodo substituent afforded a mixture of products under similar conditions arising from the competing lithium-halogen exchange and/or the displacement of the halogen atom with organolithiums used, but they were converted selectively to benzyllithiums in ether without affecting halogen substituents on the benzene ring.Several allyllithiums including dilithioisobutene were generated from allylic halides in a similar way via allylic tellurides.Wurtz-type coupling was negligible in any reactions examined. Key words: Tellurium; Lithium; Allyl; Benzyl; Halide