Stereodivergent Hydrosilylation, Hydrostannylation, and Hydrogermylation of α-Trifluoromethylated Alkynes and Their Synthetic Applications

Stereoselective hydrometalation reactions of aryl- and alkyl-substituted trifluoromethylated alkynes with triethylsilane, tributylstannane, and triphenylgermane have been investigated. ( E )-α-CF 3 -Vinylsilanes, -stannanes, and -germanes were obtained under palladium-catalyzed conditions whereas the corresponding ( Z )-α-CF 3 -vinylgermanes were obtained under radical conditions. These reactions proceed in good to excellent yields and possess a broad functional group tolerance. Applications of the ( Z )- and ( E )-α-CF 3 -vinylgermanes in palladium-catalyzed cross-coupling reactions with aryl halides having diverse electronic requirements were also investigated. The corresponding ( Z )- and ( E )-α-CF 3 -styrenes were obtained as single isomers, thus demonstrating the utility of these versatile synthons for the synthesis of stereodefined trifluoromethylated alkenes.