Pechmann Pyrazole Synthesis

H. v. Pechmann, Ber. 31, 2950 (1898).

Formation of pyrazoles from acetylenes and diazomethane. The analogous addition of diazoacetic esters to the triple bond yields pyrazolecarboxylic acid derivatives:

R. A. Raphael, Acetylenic Compounds in Organic Synthesis (London, 1955) p 179; T. L. Jacobs, Heterocyclic Compounds 5, 70 (1957); B. Eistert et al., Houben-Weyl 10/4, 840 (1968). Cf. Knorr Pyrazole Synthesis.