Cu1.5PMo12O40‐catalyzed condensation cyclization for the synthesis of substituted pyrazoles

A convenient and direct approach has been developed for the preparation of pyrazole derivatives by the condensation cyclization of hydrazines/hydrazide and 1,3‐diketones in the presence of Cu 1.5 PMo 12 O 40 (0.33 mol%) under mild conditions (r.t.‐60 °C, 10–30 min). Notably, the reaction was found to be scalable as 99% yield was obtained when the reaction was performed at a 5‐mmol scale. This solvent‐free and halogen‐free catalytic system represents an effective economic and environmentally friendly method for the construction of pyrazoles.