Préparation et Propriétés de Quelques Dérivés de L'hydrazine IV. Sur la Préparation de L'amino‐4 Urazole et de la p‐Urazine

Abstract

The thermal decomposition of phenyl carbazate results in formation of 4-amino urazole. The same compound is formed in reactions which according to other authors yield p-urazine. This six-membered cyclic isomer could not be prepared. The structure of 4-amino urazole is confirmed by study of infrared spectra and its reaction with acetone and benzaldehyde.The reaction of urea with the carbohydrazide has also been studied.Au cours d'une publication antkrieure (I), nous avons signal6 que le carbazinate de phbnyle, chauff6 A une temperature ti peine supdrieure i i 800, se d6composait facilement en phCnol et en une substance de formule C2H4N402. 2

Triazolinediones as Highly Enabling Synthetic Tools

“…Suitable experimental conditions have been developed for a range of 4-aryl- ,, and 4-alkyl-substituted ,,,, urazoles, including polyurazoles derived from aliphatic polyamines (Scheme a). ,,, In the case of 4-(4-alkyl)­phenylurazoles, it should be noted that the yield decreases with increasing carbon number of the alkylaniline, an issue that is not apparent in the case of aliphatic amines . Also, hydrazine can be used as starting material, resulting in the expected 4-aminourazole (Scheme a, R 1 = NH 2 ). − …”

“…However, in most cases this alternative two-step synthesis is not a solution. Efficient examples of this approach are mostly limited to the synthesis of 4-aminourazoles, ,− 4-methylurazoles, , and a few arylurazoles. − , Furdik et al have reported a general synthesis of 4-alkylurazoles in moderate to high yields (52–94%) from 1,6-dialkylbiureas, but the reported yields have been found to be hard to reproduce in later studies. , Relying on similar reactivity, amines have also been directly condensated with 1,2,4-triazolidine-3,5-dione ( 3 ) at elevated temperatures, thus giving the corresponding 4-substituted urazoles (Scheme c). For most substrates, the isolated yield of 4-alkylurazoles in this transimidation approach is lower than in the corresponding amine–biurea condensation–cyclization .…”

“… a R 1 = NH 2 /R 2 = H, ,, R 1 = R 2 = NH 2 , , R 1 = R 2 = Me, R 1 = Ar/R 2 = H. , b R 1 = cyclohexyl or 4-aminocyclohexyl. , …”

“…The protocols discussed in this section were mainly developed for a very specific purpose, such as the ability to synthesize urazoles bearing certain functionalities that are not tolerated by the more conventional methods. In selecting examples for this section, a number of alternative approaches were found that are either very low-yielding, limited to only one substrate, or have been simply reported as an unexpected side reaction. ,,,,− These types of reports were thus not included in this section.…”