Reaction of diazonium salts with nitrite anion

6 REACTION OF DIAZONIUM SALTS WITH NITRITE ANION 

Sandmeyer-type reactions are a useful route to polynitroarylenes with unusual substitution patterns. In these reactions an arylamine is treated with a source of nitrous acid to form an intermediate diazonium salt which is readily displaced on reaction with a suitable nucleophile. Many substituents can be incorporated into the aromatic ring via this method, including the nitro group. 

Nitration via diazotisation has been extensively used for the synthesis of isomeric dinitronaphthalenes. Ward and co-workers used nitration via diazotisation to prepare 3,3, 4,4 -tetranitrobiphenyl from 3,3 -dinitrobenzidine, and 3,4,5-trinitrotoluene from 3,5-dinitro-4-toluidine. Ward and Hardy prepared 1,4,6-trinitronaphthalene from 4,7-dinitro-1-naphthylamine. Korner and Contardi used the nitrate salts of aryldiazonium compounds for the synthesis of polynitro derivatives of benzene and toluene. Accordingly, 

4- and 1,2,3-trinitrobenzenes were formed from the isomeric 2,4- and 2,6-dinitroanilines respectively. In a similar way, 3,4,5-, 2,3,5-, ° and 2,3,6- trinitrotoluenes were prepared from the isomeric dinitrotoluidines. Holleman used a similar route for the conversion of picramide (53) to 1,2,3,5-tetranitrobenzene (54) in 69 % yield. Such examples illustrate why nitration via diazotisation is a useful route to polynitroarylenes - products not available from the direct nitration of aromatic substrates can be synthesized. 

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