Synthesis of biaryls involving aryllead IV tricarboxylates

Concerning the reaction mechanism, the factors having the profound influence on the reactions are the nucleophilicity of arene and electrophilicity of aryllead(IV) reagent. Electron-donating groups increase an electron-density of the arene, and thus enhance its reactivity. 

Beside haloacetic acids, this reaction can be strongly accelerated by aluminum chloride, trifluoroacetate, Al(OCOCF2CF3)3, or Al(OCOCF2CF2CF3)3 (8 eq. to ArPb(OAc)3). These fluorinated carboxylic salts were readily prepared by careful addition of the given acid to resublimed aluminum chloride [65]. These catalysts allow to perform the arylation with less reactive arenes such as toluene and benzene. The main side-reaction which occurs during the aryllead(IV) tricarboxylates involving reactions in trifluoroacetic acid is the protodeplumbylation. This reaction produces the parent arene by protonation of aryllead(IV) compound, and may become the major process [65,66]. 

Whereas the aryllead(IV) tricarboxylates in the above mentioned arylation reactions of electron-rich arenes act as aryl-cation donors, in the palladium-catalysed cross- 

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