Alkylation of Allylic Derivatives. 17. Cross-Coupling Reactions of Diallylic Pivalates with Butyl- and Phenylcopper Reagents

Article abstract of DOI:10.1021/jo00007a055

Cross coupling (Z)-1-phenyl-1,4-pentadien-3-yl pivalate (cis-1-OPiv) with LiCuBu2, LiCu(CN)Bu, LiCuPh2 and LiCu(CN)Ph gives only the fully conjugated γ-coupling product.With LiCuBr2 substantial loss of double-bond configuration occures to give primarily the all-trans coupling product.With other cuprates, no detectable loss of double-bond configuration was observed.Cross coupling (Z)-3-(2-phenylethenyl)-2-cyclohexen-yl pivalate (cis-18-OPiv) with LiCuBu2, LiCuPh2, and LiCu(CN)Ph gives only α coupling product; with LiCu(CN)Bu, a mixture of α, γ, and ε coupling product was obtained.Cross coupling with LiCuBu2 results in loss of double-bond configuration in the α-alkylation product.With other cuprates, no loss of double-bond configuratiuon was detected in the α and γ coupling product.These results have profound mechanistic implications, which are discussed.The relationship between structure and reactivity was also investigated.A variety of diallylic pivalates (1-5-OPiv) were prepared and cross coupled with LiCuBu2, LiCu(CN)Bu, LiCuPh2, and LiCu(CN)Ph.Generally, coupling occurs at the least-substituted allylic system; mechanistic implications are discussed.