Ring Cleavage of 4-(4-Nitrophenylazo)-substituted Pyrazolidine-3,5-diones to α-(4-Nitrophenylhydrazono)semicarbazides with Consecutive Reactions

Article abstract of DOI:10.1002/prac.19953370147

The reaction of 1 and 2 with ammonia, methylamine and dimethylamine in aprotic solvents, e.g. diethyl ether, yields the compounds 3-8 which can exist in two isomeric forms (form a/b).On conditions which are usually chosen for spectroscopic investigations only form a could be detected.Nevertheless, under the influence of bases like KOH or ammonia in water or alcohol these compounds are mainly converted to semicarbazides (11-15) which means that this reaction must run via form b.Those semicarbazides which are unsubstituted at the N-4 of their semicarbazide-moiety show great tendency to cyclize, thus forming the triazole-derivatives 16-18.In contrast to these products, in the case of the N-4-monomethylated semicarbazide 14 the six-membered heterocyclus 19 was obtained.In comparison with 1 and 2, stable intermediates such as 3-8 in the reaction with 21 could not be isolated.