An efficient stereoselective preparation of cis-perfluoroalkenylzinc reagents [(E)-RFCF{double bond, long}CFZnCl] by the metallation of 1H,1H-perfluoroalkanes and their derivatization to cis-1-arylperfluoroalkenes [(Z)-RFCF{double bond, long}CFAr]

Article abstract of DOI:10.1016/j.jfluchem.2005.12.022

Various 1H,1H-perfluoroalkanes (R_FCF₂CH₂F, R_F = CF₃, C₂F₅, C₄F₉, C₅F₁₁, C₆F₁₃, C₁₀F₂₁) were metallated using LDA in a THF solution of ZnCl₂ at RT or -78 °C to produce the corresponding perfluoroalkenylzinc reagents (R_FCF{double bond, long}CFZnCl) in a cis-selective fashion. An increased yield (75-83%) and cis-selectivity (>89%) of the perfluoroalkenylzinc reagents were observed for metallation reactions performed at -78 °C. The cis selectivity was excellent for 1H,1H-perfluoroalkanes with larger R_F groups (C₄F₉, C₅F₁₁, C₆F₁₃, >96%). The cis-perfluoroalkenylzinc [(E)-R_FCF{double bond, long}CFZnCl] reagents were coupled with aryl iodides to obtain cis-1-arylperfluoroalkenes [(Z)-R_FCF{double bond, long}CFAr] in 71-95% isolated yields. The cis-perfluoroalkenylzinc reagents upon iodinolysis produced cis-1-iodoperfluoroalkenes [(E)-R_FCF{double bond, long}CFI] in 68-70% isolated yield.