A novel method for (Z)-stereoselective preparation of CF3-substituted enediynes and their coupling reactions

Trifluoromethylated enynyl sulfones 3 were reacted with 2-4 equiv of phenyl, n-hexyl, trimethylsilyl, or triisopropylsilyl substituted ethynyllithium reagents in THF or ether at 0 °C to give trifluoromethylated enediynes 6 (Z)-stereoselectively in 41-96% yields. The reactions of β-fluoro-β-trifluoromethylvinyl sulfone 5 with same ethynyllithium reagents (4 equiv) afforded the corresponding enediynes 6 in 41-90% yields. The cross-coupling reactions of 6 bearing TMS group with aryl iodides in the presence of Pd(PPh₃)₂Cl₂, Ag₂CO₃, and n-Bu₄NBr provided the corresponding enediynes 6 in 20-71% yields. Dimerization of (Z)-6 bearing TMS group in the presence of CuBr₂ and K₂CO₃ yielded dimer (Z,Z)-7 in good yield.