5- Bromo-2,3-diaminopyridine, reaction with

Diaminopyridine has been condensed with glyoxal, benzil, - diacetyl,and the pyridils 4. ° Ethyl oxalate yields the 2,3-dioxo compound. The conditions employed for these condensations can be critical. Thus glyoxal in neutral solution yields an unidentified, insoluble, infusible solid, whereas in the presence of acetic acid the reaction readily provides the parent heterocycle.The preferred method makes use of glyoxal sodium bisulfite. Many symmetrical dicarbonyl compounds have been condensed with a variety of 2,3-diaminopyridines substituted in the pyridine ring by bromo, ° chloro, methyl, " or combinations of these substituents. ... 

The preparation and reactions of 3-bromo-4,S-diaminopyridine have been studied. The nitration of 4-amino-3-bromopyridine (IX-182) and the subsequent rearrangement of the nitramino derivative IX-183 give 4-amino-3-bromo-S-nitro-pyridine (IX-184). The reduction of IX-184 with iron and acetic acid produces... 

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