Metal-halogen exchange substitution reactions

4- tributylstannylpyrazoles with aryl iodides or A -trityl-protected 4-iodopyrazoles with aryltributylstannanes 1997S563 . 4-(5-iodo-3-methylpyrazolyl)phenylsulfonamide 416 served as an efficient template for the preparation of Suzuki-coupled 

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The exploration of DoM chemistry in haloheteroaromatics is valuable for two reasons (a) halo derivatives can be readily prepared from acessible amino, hydroxy, and, at times, unsubstituted systems, and (b) halogens can be subsequently induced to undergo a variety of funcionalizations via addition-elimination, metal-halogen exchange, SRN1, and cross coupling reactions. Some of these transformations are more facile than in the aromatic series. Thus, DoM tactics may lead to diverse substituted heteroaromatics, which can be difficult to obtain by more classical means. 

Halogen functionality in heteroaromatics undergoes a variety of transformations by nucleophilic substitution metal-halogen exchange, radical substitution, and cross coupling reactions. The connecting link between these processes and the DoM reaction is therefore a powerful tool in heterocyclic chemistry. 

Species IV were prepared from -bromophenoxy-substituted phosphazene trimers and high polymers, by metal-halogen exchange to yield the -lithio-derivative, followed by reaction with diphenylchlorophosphine. Both cyclic trimers and high polymers containing the pendent phosphine reacted with H2Os(CO)3q,... 

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