Ortho metal-catalyzed generation

Many arylations are assisted by functional groups that promote ortho-metallation. Thus, for example, acetanihdes react with arylsilanes at the ortho position via pal-ladacycles 78 and 79 to form derivatives 80 (Scheme 11.27) [84]. Mechanistically, this transformation is similar to a cross-coupling reaction, in which the oxidative addition step is replaced by the ortho-metallation, although in this case the Pd(0) intermediate must be oxidized in situ to generate the reactive Pd(ll) species. Unsubstituted benzylamines and N-methylbenzylamine are ortho-arylated with Pd(OAc)2 in the presence of trifluoroacetic acid (TFA) and silver acetate [85], and a mechanism which differs from the usual Pd(0)/Pd(II) catalytic cycle was suggested for this. Ortho-alkylation was also observed in the palladium-catalyzed... 

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