Olefination of Aryl Halides Mizoroki-Heck Reaction

Mechanism of the Olefination of Aryl Halides (Mizoroki-Heck Reaction) 

During the past decade, many metallacyclic palladium(II) precursors have been studied as catalysts for the Heck reaction. Although some initial claims were made that these compounds must act as catalysts for the Heck reaction and other cross couplings by a new mechanism involving oxidative addition to palladium(II) and olefin insertion into an arylpalladium(IV) complex, - subsequent studies have shovm that these complexes are reduced to palladium(O) complexes by one of several processes that cleave the Pd-C bond of the metallacycle prior to the catalytic process. - The turnover numbers of reactions initiated with palladacyclic catalysts are high, but the rates of reactions catalyzed by these complexes tend to be lower than those initiated with related palladium(O) complexes. -  

Mechanism of the Individual Steps of the Cross-Coupling Process 

The fundamental information on the individual steps of these cross-coupling reactions was included in Chapters 6, 7, 8, and 9 on oxidative addition, reductive elimination, and migratory insertion. Details of the transmetallation step are less established, but some of the current data on this step are presented in this chapter in Section 19.4.2.2. 

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