A series of compounds 8a-e, was synthesized by condensation of compounds 7a-e with ethyl bromoacetate. The treatment of compounds 8a-e with hydrazine hydrate afforded the corresponding hydrazide derivatives (9a-e). Subsequently, compounds 9a-e were converted to alkylidene hydrazides (10a-e). Moreover, upon heating in the presence of carboxylic acids, compounds 9a-e unexpectedly gave 1,4-dihydro-[1,2,4,5]tetrazine derivatives (11a-e).
DEMİRBAŞ, AHMET (2004) "A Convenient Synthesis of 3,6-Disubstituted-1,4-Dihydro-[1,2,4,5]Tetrazines and Preparation of New Acetic Acid Derivatives Containing 5-Oxo-4-Phenylamino- 4,5-Dihydro-[1,2,4]Triazole," Turkish Journal of Chemistry: Vol. 28: No. 3, Article 6. Available at: https://journals.tubitak.gov.tr/chem/vol28/iss3/6