Palladium-catalyzed cross-coupling with related compounds

Phenols, much like anilines, represent important synthons for the constraction of biologically active compounds and functional materials. " Moreover, the phenol moiety itself is present in a number of top selling pharmaceuticals with diverse function selected examples are depicted in Figure 3. The use of water, or related MOH salts, as nucleophiles in palladium-catalyzed cross-couplings involving (hetero)aryl halides conceptually represents a mild and selective route to phenols that is complementary to more established phenol syntheses, " " including oxidative protocols. However, the difficulties associated with realizing such transformations mirror those... 

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. - ... 

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