Organothallium compounds arylation

The aryl-thallium bond is thus apparently capable of displacement either by electrophilic or by suitable nucleophilic reagents. Coupled with its propensity for homolytic cleavage (spontaneous in the case of ArTlIj compounds, and otherwise photochemically induced), ArTlXj compounds should be capable of reacting with a wide variety of reagents under a wide variety of conditions. Since the position of initial aromatic thallation can be controlled to a remarkable degree, the above reactions may be only representative of a remarkably versatile route to aromatic substitution reactions in which organothallium compounds play a unique and indispensable role. 

The ligand coupling and ligand transfer mechanisms explain a number of transformations of organothallium compounds. The best studied reaction is the carbon-iodine conversion for the synthesis of aryl iodides, but other efficient conversions have been also described. 

Organothallium compounds are useful because they react with potassium iodide and potassium cyanide to afford aryl iodides and nitriles, respectively (Scheme 10.10). This route offers an alternative to diazoni-um chemistry (see Chapter 8) for the introduction of these functional groups. 

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