Pyrazoles and tetrahydroindazoles may be prepared by condensation of 1,3-diones and hydrazines under layered zirconium sulfophenyl phosphonate catalysis, in solvent-free conditions.
Tungstate sulfuricacid‐catalyzed Knorr reaction have been used as a simple, rapid, atom economic and green method for the synthesis of indazole and pyrazole derivatives based on the condensation of hydrazine derivatives and ß‐dicarbonyl compounds under solvent‐free conditions. It was found that the catalyst could be recovered and reused without significant loss of its activity. The use of this method