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 Cu1.5PMo12O40 (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. Cu1.5PMo12O40 was found to be an effective, inexpensive and green catalyst for the preparation of pyrazole derivatives by the condensation–cyclization of hydrazines and 1,3‐diketones under mild conditions (room temperature to 60°C, 10–30 min). [ABSTRACT FROM AUTHOR]