Neat synthesis of octahydroxanthene-1,8-diones, catalyzed by silicotungstic acid as an efficient reusable inorganic catalyst.

In this article, the first use of silicotungstic acid (HSiWO) as a catalyst for the synthesis of octahydroxanthene-1,8-diones by the reaction of 5,5-dimethylcyclohexane-1,3-dione (dimedone) with various aldehydes under thermal solvent-free conditions is described. The obtained results showed that the catalyst has a high catalytic activity, and the desired products were obtained in high yields. Moreover, the catalyst was found to be reusable, and a considerable catalytic activity still could be achieved after the fifth run. Easy work-up and avoidance of using harmful organic solvents are the other advantages of this simple procedure. [ABSTRACT FROM AUTHOR]