Synthesis of 5-amino-pyrazol-4-N’-[bis(metylthio)- methylene]carbohydrazide

Abstract

The synthesis of pyrazolic ring systems has been widely studied in the last years with the purpose of finding new molecules with potential biological activity. It has been certainly achieved since now a days, several medications contain this kind of structures as active principle. Between them, analgesics, antiinflammatories, and sedatives are to be emphasized. In this work, the synthesis of new compounds of 5-aminopyrazolic structure by means of the reaction between the alkene and dithiethane push pull derived from N'-[bis(methylthio)methylene]-cyanoacethydrazide and appropriate dinucleophiles is reported. The best results were achieved by reaction of the alkene push pull N'-[bis(methylthio)methylene]-2-cyano-3,3-[bis(methylthio)]acrylhydrazide with hydrazine and hydrazide when an excess of the dinucleophiles was used (1:2.5). The intramolecular cyclization occurring in the reaction intermediate takes place without participation of the amidic carbonyl, which shows the greater reactivity of the cyano group regarding the NH attack. The results allow to verify the greater push pull character of the ethylene bond than the azometinic one for the reason that in the former the polarized bond will be more stabilized. It could be demonstrated in general, that the better yields were achieved by using the keten-S,S-acetals as electrophilic agents. The goal compounds could be obtained in just one step with higher yields than the reported for similar ring systems. The characterization of the products was carried out by means of elemental quantitative analysis and several spectroscopic methods: Infra Red and Nuclear Magnetic Resonance Spectroscopies and Mass Spectrometry.