NaHSO4–SiO2 Promoted Solvent-Free Synthesis of Triazolo [1,2-a]indazole-triones

A new one-pot, efficient three-component condensation of dimedone, urazole and aromatic aldehydes in the presence of silica supported sodium hydrogen sulfate as an effective heterogeneous catalyst for the synthesis of novel Triazolo[1,2-a]indazole-1,3,8-trione derivatives under solvent-free conditions is described.