Negishi Coupling

Negishi coupling uses Zinc with a Palladium or Nickel catalyst to create carbon-carbon bonds. 

The reaction is moisture and air sensitive and is generally faster than reactions using organostannanes and organnoborates because of the reactiveness of organozinc compounds. 

Negishi coupling is not used in industry as much as the Suzuki and Heck reactions due to the reaction sensitivity.

Mechanism

R = aryl, alkyl, alkynyl, vinyl, benzyl

R' = aryl, allyl, alkyl, benzyl, vinyl

Where order of reactivity is allyl, benzyl, vinyl, aryl, alkyl

Stereoselectivity

The stereoselectivity of Negishi Coupling usually depends on the metal catalyst. With the palladium catalyst, the configuration of each carbon double bond is retained.

Examples

Acyl Halides; >90% yield when R=Nbu, Ph, Alkynyl

63% Yield

PDE472 Synthesis, phospodiesterase inhibitor invesitgated in the treatment of athsma