[摘要]:(Heterocyclic Compounds (More Than One Hetero Atom)) Section 2-Pyrazolin-5-ones (tautomers to 5-hydroxypyrazols) bearing dialkylaminoyalkyl substituents at the ring nitrogen atom N-1 are prepd. from the corresponding hydrazines and beta-ketoesters. Detailed NMR spectroscopic investigations (1H, 13C, 15N) with the obtained compds. are undertaken and the tautomerism of such pyrazolones in soln. is discussed.