Microwave-Assisted Synthesis of Spirofused Heterocycles Using Decatungstodivanadogermanic Heteropoly Acid as a Novel and Reusable Heterogeneous Catalyst under Solvent-Free Conditions

Decatungstodivanadogermanic acid (H6GeW10V2O40·22H2O) was synthesized and used as a novel, green heterogeneous catalyst for the synthesis of spirofused heterocycles from one-pot three-component cyclocondensation reaction of a cyclic ketone, aldehyde, and urea in high yields under solvent-free condition in microwave irradiation at 80°C. This catalyst is efficient not only for cyclic ketones, but also for cyclic β-diketones, β-diester, and β-diamide derivatives such as cyclohexanone, dimedone, and Meldrum's acid, or barbituric acid derivatives