Azides aryl, from diazonium salts

Aryl azides from diazonium salts and /7-toluenesulfonamide 266 An aromatic monoamine (1 mole) or diamine (0.5 mole) is dissolved in concentrated hydrochloric acid (2.5 moles), and the resulting solution or suspension of the amine hydrochloride is diazotized with the calculated amount of sodium nitrite. The diazonium salt solution is mixed with a solution of / -toluenesulfonamide (1 mole) and sodium hydroxide (5 moles) at —5° and set aside for 24-48 h, then brought to pH 8 and extracted with ether. The azide is distilled as above. Solid azides, however, are filtered off and washed with ether. 

The successful synthesis of these compounds showed the feasibility of using the carbodiimidazole coupling reaction in the formation of aryl-azido ATP analogs. For the general synthesis of the arylazidocarboxylic acids, 4-fluoro-3-nitroaniline is first diazotized in a concentrated hydrochloric acid medium in the presence of sodium nitrite [Eq. (2)]. The diazonium salt is subsequently treated with sodium azide, which results in the formation of a light-sensitive 4-fluoro-3-nitrophenyl azide (IV) [Eq. (3) ]. The structure of (IV) has been confirmed by its melting point of 52°-52.5° (recrystallized from petroleum ether) its NMR spectrum, 7.47 ppm (2 protons), 7.78 ppm (1 proton) and its mass spectrum, m/e 182. 

The dry azide salt exploded violently with a brilliant flash [1]. Subsequent reports claim it impossible to isolate arenediazonium azides, the attempt giving usually the aryl azide or, under very specific conditions, some arylpentazole. Hantzsch had considered both possibilities and produced qualitative evidence against them. He started from the nominal diazonium hydroxide in dry ether, an unusual azo-coupling method. Whatever he got appeared to revert to the diazonium hydroxide on treatment with alkali [2]. 

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