Knorr Pyrazole Synthesis

L. Knorr, Ber. 16, 2587 (1883).

Formation of pyrazole derivatives from hydrazines, hydrazides, semicarbazides, and aminoguanidines by condensation with 1,3-dicarbonyl compounds; substituted hydrazines yield two structurally isomeric pyrazoles:

T. J. Jacobs, Heterocyclic Compounds 5, 46 (1957); M. H. Palmer, Structure and Reactions of Heterocyclic Compounds (Arnold, London, 1967) pp 378-385. Cf. Pechmann Pyrazole Synthesis.