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-CF3-Vinylsilanes, -stannanes, and -germanes were obtained under palladium-catalyzed conditions whereas the corresponding (Z)-α-CF3-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-CF3-vinylgermanes in palladium-catalyzed cross-coupling reactions with aryl halides having diverse electronic requirements were also investigated. The corresponding (Z)- and (E)-α-CF3-styrenes were obtained as single isomers, thus demonstrating the utility of these versatile synthons for the synthesis of stereodefined trifluoromethylated alkenes.