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

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.

Rhodium-catalyzed [2+2+2] cycloaddition of various fluorine-containing alkynes--novel synthesis of multi-substituted fluoroalkylated aromatic compounds.

Treatment of various fluorinated internal alkynes with 10 mol% of RhCl(3).H(2)O and 30 mol% of i-Pr(2)NEt in toluene at the reflux temperature for 18 h gave the corresponding trimerization products as an isomeric mixture in high yields. Cycloaddition using 1.0 equiv. of fluorinated alkynes and 2.0 equiv. of non-fluorinated alkynes under the same reaction conditions as in the trimerization led to mono- and bis-fluoroalkylated benzene derivatives in high yields, together with small amounts of trimerization products. The reaction of fluorine-containing bispropargyl ether with non-fluorinated alkynes took place smoothly to afford the corresponding bicyclic molecules in good to high yields.

An efficient protocol for the stereoselective construction of multisubstituted fluorine-containing alkenes. A palladium-catalyzed bisstannylation of fluorinated internal alkynes.

On treatment of various fluorinated internal alkynes with 1.2 equiv of hexabutylditin under the influence of 2.5 mol % of Pd(t-BuNC)(2)Cl(2) in THF at room temperature for 4 h, the bisstannylation proceeded smoothly to afford the corresponding bisstannylated cis-adducts in high yields. Thus obtained adducts were subjected to the Stille cross-coupling reaction to give the corresponding tetrasubstituted fluorine-containing alkenes with defined stereochemistry in good yields.