Hirao coupling

In organic chemistry, Hirao coupling is a chemical reaction for the formation of carbon-phosphorus bonds using palladium cross-coupling. Hirao coupling expands the scope of carbon-phosphorus bond formation from alkyl (sp3) carbon-phosphorus bonds to sp2 (alkenyl and aryl) carbon-phosphorus bonds. This builds on previous work by August Michaelis and Alexandr Arbuzov, who developed the Michaelis-Arbuzov reaction to deliver alkyl phosphonates from alkyl halides and phosphinites in 1898. Earlier work used nickel halides (NiX2, X = Cl, Br) as catalysts at high temperatures to achieve vinyl phosphonates, but these reactions often proceeded in low yields and poor stereoselectivity.