Untersuchungen zur Ringspaltung 4-(4-nitrophenylazo)-substituierter Pyrazolidin-3,5-dion-Derivate

Studies on Ring Cleavage of Some 4-(4-Nitrophenylazo)-substituted Pyrazolidine-3,5-dione-Derivatives Continuing to previous investigations the ring cleavage of the pyrazolidine compounds 3 and 7 is studied under the influence of KOH and CH₃ONa. Due to the different substitution of atoms of the heterocyclus this reaction was expected to result in at least two isomeric compounds. Actually this assumption was only confirmed for 3 . So the reaction of 3 with CH₃ONa yields a mixture of four isomers ( 4a - 4d ) with 4a as main product. On the other hand, when 7 is treated with CH₃ONa or KOH only one product is formed. With regard to the great structural similarity of the possible isomers, mass spectroscopy proved to be the best test of whether the ring cleavage occurs between C-3 and C-4 or C-4 and C-5 of the heterocyclus.