Stereospecific lithium-halogen exchange of alkenyl iodides was performed upon treatment with butyllithium in non-polar solvents such as hexane, benzene, and toluene at 25 °C to provide alkenyllithiums quantitatively with retention of the configuration. Metal-iodine exchange of allenyl iodides with n-BuLi, i-PrMgBr or Et2Zn was also performed effectively to afford the corresponding allenylmetallic reagents
Olefination of carbonyl compounds with gem-dizincioalkanes, bis(iodozincio)methane, 1,1-bis(iodozincio)ethane, and bis(bromozincio)methyltrimethylsilane, afforded the corresponding olefins in good to excellent yields.
Partial reduction of alkynes to (Z)-alkenes is achieved with the low-valent group 5 metal reagents prepared from MtlCl5 (Mtl = Nb or Ta) and zinc in a mixed solvent of DME (or THF) and benzene.
The reduction of alkenyl halides with tributyltinhydride in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium has been studied. Alkenyl iodides reacted easily with tributyltinhydride at 25°C to give the corresponding hydrocarbons stereoselectively. However, the reaction of alkenyl bromides were sluggish at 25°C and needed heating at 75°C to complete.
A NEW STEREOSELECTIVE SYNTHESIS OF VINYLSILANES UTILIZING VINYL SULFONES
作者:Masahito Ochiai、Tatsuzo Ukita、Eiichi Fujita
DOI:10.1246/cl.1983.1457
日期:1983.9.5
Vinylsilanes 3 were prepared stereoselectively from vinyl sulfones via the formation of β-tributylstannyl sulfones 2. The stereochemistry of 3 was controlled by the choice of the method for the destannylsulfonation of 2.