Diazotization of amino compounds

The stabilities of pyridine-2- and -4-diazonium ions resemble those of aliphatic rather than benzenoid diazonium cations. Benzenediazonium ions are stabilized by mesomerism (726) which 

The reactions of 3-amino groups in pyridines and 5-amino groups in pyrimidines, by contrast, are close to those of the amino group in aniline. The diazonium salts are reasonably stable and undergo coupling and replacement reactions and can be reduced to hydrazines. Amino groups in the 3-position of isoquinolines (727) are subject to bond fixation and react in a manner intermediate between those of a- and p-amino groups they can be diazotized under the conditions normally employed. 

Aminopyridine /V-oxides can be diazotized, and the diazonium salts undergo coupling, etc. These diazonium salts are stabilized by mesomerism (728), cf (726). Amino groups in pyridazine /V-oxides can also be diazotized and the diazonium group further replaced by other functionality. Nitrosation of 3-amino-1,2,4-triazine 2-oxides and subsequent thermolysis of the diazonium tetrafluoroborate salts afforded 3-fluoro-1,2,4-triazine 2-oxides (85H(23)1969). 

P-Aminopyridones form diazo anhydrides (e.g. 729) (cf aminophenols) which on irradiation give pyrrolecarboxylic acids (731) via (730). 

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Synthesis of diazonium salts. The conventional diazotization of amino compounds is performed as described below. An amino compound is dissolved in acidic water, then aqueous sodium nitrite is added dropwise to the solution, while the solution temperature is kept below 0V. After completion of... 

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