Olefinic alkyllithiums preparation

This ether is prepared by the Williamson ether synthesis from alcohols and phenols using a-bromomethylstyrene. It is cleaved by treating the ether in THF with f-BuLi at —78°C for 30 min (75-97% yield). The phenallyl ether can be cleaved in the presence of an allyl ether. Phenallyl amines and amides are cleaved similarly. Cleavage occurs by an addition of the alkyllithium to the olefin followed by elimination. 

The cleavage of alkyl phenyl sulfides by naphthalenelithium or a lithium dispersion in THF to afford alkyllithium reagents has been studied initially by Screttas and Micha-Screttas [309,310) as part of their hydrolithiation of a-olefins process. They prepared primary, secondary and tertiary alkyllithium reagents in fair to good yields, as shown by carbonation. 

Shapiro reaction. (2, 418-419 6, 598-600). Several laboratories have used EDA instead of an alkyllithium for decomposition of tosylhydrazones of ketones to olefins. Trisubstituted alkenes can be prepared by this modification in moderate yields from tosylhydrazones that contain only tertiary a-hydrogens. This modification also favors formation of the (Z)-disubstituted olefin. ... 

The reaction is extended to the synthesis of arylacetylenes and stereodefined enynes. The reactions sequence involves the preparation of thermally stable lithium complexes from B-OMe-9-BBN and alkyllithium in THE at -78 C. These complexes undergo Pd-catalyzed Suzuki coupling to both aromatic and olefinic substrates to produce a variety of alkynyl derivatives and enynes, with complete retention of the double bond geometry (Eq. 31.4) [4a]. 

Vinyl halides react with alkyllithiums with the aid of a palladium(O) complex to give olefins stereospecifically in good yields. When Grignard reagents are employed instead of alkyllithium compounds, these reactions can be carried out catalytically with the palladium complex (Yamamura et al., 1975). or/Ao-Alkylated thiobenzophenones can be similarly prepared from 5-donor ligand or/Ao-metalated complexes (H. Alper and J. Kamenof, unpublished results). 

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