Hiyama coupling

In organic chemistry, a Hiyama coupling is a palladium or nickel-catalyzed cross coupling reaction of organosilanes with organic halides or triflates. Hiyama couplings were first reported by Yasuo Hatanaka and Tamejiro Hiyama in 1988.

Typically, the Hiyama coupling reaction is promoted by activation of the organosilane with fluorides. The reaction possesses many advantages such as low environmental impact, high atom efficiency, and safe handling compared with the coupling reactions of organoboron, organozinc, or organotin compounds.

In the original 1988 publication 1-iodonaphtalene was reacted with trimethylvinylsilane to 1-vinylnaphtalene with catalyst the allylpalladium chloride dimer dissolved in HMPA and TASF reagent as fluorine source.


 * [[Image:Hiyama coupling.png|500px|Hiyama coupling]]

The reaction proceeds through the usual oxidative addition, transmetalation, trans-cis isomerization and reductive elimination sequence. The purpose of the fluorine is to activate the silicon compound RSiR'3 to a RSi-R'3F intermediate which is more amiable to transmetalation. Without the added fluorine the organosilicon compound is simply too stable.

In one extension the alkenylsilane is prepared in situ from a terminal alkyne and tetramethyldisiloxane or hexamethylcyclotrisiloxane.

In another extension the reaction is assisted by nickel chloride, LiHMDS and norephedrine with caesium fluoride as fluorine donor :


 * [[Image:HiyamaCouplingExtension.png|400px|Hiyama reaction extension Strotman 2007]]