A novel synthesis of 1,6-diamino-2-pyridones and [1,2,4]triazolo[1,5-a]pyridine derivatives

3-Cyano-1,6-diamino-2-pyridone derivatives (3) possessing various alkoxycarbonyl groups are prepared directly from the reaction of dialkyl (E)-2,3-dicyanobutendioates (1) with cyano-acetohydrazide (2). The resulting diamine (3) (R = Et) is readily cyclized to 8-substituted [1,2,4]triazolo[1,5-a]pyridine derivatives (5) in high yields by treatment with orthocarboxylic esters (4) such as trimethyl orthoformate or triethyl orthoacetate etc. Furthermore, 3-cyano-6-amino-2-pyridones (6) are although obtained in excellent yields by the reductive deamination of 3. The structural study of 6 was carried out by spectroscopic methods in some details.