Palladacycles are used as pre-catalysts, usually by the reductive elimination from palladium(II) to the catalytically active palladium(0). In the example of 2-aminobiphenyl palladacycles, a kinetically active 12-electrons Pd(0) species is formed, allowing for further oxidative addition with reactants. A series of 2-aminobiphenyl bearing various X and L groups were synthesized to better understand the electron/steric effect.
By employing palladacycles as pre-catalysts, high reactivity and selectivity have been achieved in Heck reaction[2] and a variety of cross-coupling reactions, such as Suzuki, Sonogashira, Stille, Buchwald–Hartwig reactions.
Total synthesis containing palladacycles have been demonstrated.