2-Arylhydrazononitriles as building blocks in heterocyclic synthesis: A novel route to 2-substituted-123-triazoles and 123-triazolo45-bpyridines

摘要

2-Arylhydrazono-3-oxobutanenitriles >2 was reacted with hydroxylamine hydrochloride to yield amidooxime >3. This was cyclized into the corresponding oxadiazole >4 on refluxing in acetic anhydride. When refluxed in DMF in presence of piperidine, the corresponding 1,2,3-triazoleamine >5 was formed. The latter was acylated to >6 by addition of acetic anhydride while treatment of >5 with malononitrile gave the 1,2,3-triazolo [4,5-b]pyridine >8. Treatment of acetyl derivative >6 with DMFDMA gave enaminone >9. The enaminone >9 was coupled with benzenediazonium chloride to yield phenylazo-1,2,3-triazolo [4,5-b]pyridine >10. Trials to convert compound >14 into 1,2,3-triazolo [4,5-d]pyrimidine >15 via refluxing in AcOH/NH4OAc failed. Instead the hydrolyzed product >5 was formed.