Eingegangen am 31. M a n 1980
Structure and Chemistry of Heterocycles Capable of Tautomerism, I Synthesis and NMR Spectroscopy of Isomeric Methyl Derivatives of Diethylmalonohydrazide Sodium ethylate-catalyzed condensation of diethyl diethylmalonate with methylhydrazine yields N-methyldiethylmalonohydrazide (3), which reacts with diazomethane to give the isomeric compounds 6 and 8 . 6 is also prepared by methylation of diethylmalonohydrazide (2) with dimethyl sulfate. Due to its poor reactivity, the 0-methyl compound 7 can be obtained by the reaction of 2 with diazomethane. The suitability of the structurally fixed methyl derivatives 6 -8 as model compounds in the NMR spectroscopic study of the tautonieric structure of 2 and 3 is examined.
Cyclische Hydrazide stellen eine interessante Gruppe tautomeriefahiger Lactame dar. Arndt 1) hatte aufgrund des Reaktionsverhaltens gegeniiber Diazumethan eine generelle Tautomerisierungstendem zur unsymmetrischen Lactam-Lactim-Struktur vermutet und dies auf die ungunstige mesomere Grenzstruktur 1 der alternativen Dilactarn-Struktur zuriickgefiihrt. Im Falle des zur Aromatisierung befahigten Maleinohydrazids konnte das Vorliegen der 3-Hydroxy-6(1 H)-pyri-