| Popis: |
Homocuprates [RCuR”]MgX, 1 (R = alkyl; R” = R or BuC≡C) appeared to be useful reagents for the introduction of an R group into 1-alkynes R′−C≡C−H 2 (R′ = Ph, H, alkyl) in tetrahydrofuran as a solvent. Depending on R and R′ terminal alkenes RR′CCH24a, non-terminal alkenes E−R′CHCHR 4b or mixtures of 4a and 4b were isolated after protic work-up. Except for the reaction of t-Bu2CuMgCl with Ph−C≡C−H and t-Bu−C≡C−H only cis additions were observed. In two cases, viz. for the reaction of Me2CuMgCl and t-Bu2CuMgCl with Ph−C≡C−H, evidence was obtained for accompanying proton abstraction from the terminal alkyne 2 by the cuprate. This proton abstraction could be suppressed completely by carrying out the addition in the presence of LiBr. Moreover, a strong accelerating influence of LiBr on the rate of the R transfer from the cuprate 1 to the 1-alkyne 2 was observed. |
