A remarkable regiocontrol in the palladium-catalyzed silylstannylation of fluoroalkylated alkynes – highly regio- and stereoselective synthesis of multi-substituted fluorine-containing alkenes

Abstract

On treating fluorine-containing internal alkynes with 1.2 equiv. of (trimethylsilyl)tributyltin in the presence of 2.5 mol% of Pd(PPh₃)₂Cl₂ in THF at the reflux temperature for 6 h, the silylstannylation reaction proceeded smoothly to afford the corresponding silylstannylated adducts in high yields in a highly regio- and cis-selective manner. Switching the palladium catalyst from Pd(PPh₃)₂Cl₂ to Pd(t-BuNC)₂Cl₂ promoted the formation of silylstannylated adducts with opposite regioselectivity. The thus obtained silylstannylated adducts were subjected to Stille cross-coupling reactions to furnish the corresponding fluoroalkylated vinylsilanes whose C–Si bond was converted to a C–C bond by treating with aldehyde in the presence of TBAF and Zn(OTf)₂, the corresponding fluoroalkylated tetra-substituted alkenes being afforded in moderate to good yields with a defined stereochemistry.