Synthesis of Tetrahydrobenzo[a]xanthene-11-one Derivatives Using ZrO2- SO3H as Highly Efficient Recyclable Nano-catalyst

The catalytic effect of Zirconia Sulfuric Acid (ZrSA) nanoparticle which is synthesized from the reaction of ZrO with chlorosulfonic acid has been investigated in the synthesis of tetrahydrobenzo[a]xanthene-11-ones by one-pot three-component reaction of β naphthol, aromatic aldehydes, and dimedone. Different reaction conditions were studied in the presence of ZrSA nanoparticle as catalyst. The results showed that ZrSA exhibited high catalytic activity towards the synthesis of tetrahydrobenzo[a]xanthene-11-ones, with the desired products being formed in high yields. Furthermore, the catalyst was recyclable and could be reused at least three times without any discernible loss in its catalytic activity. Overall, this new catalytic method for the synthesis of tetrahydrobenzo[a]xanthene-11-ones provides rapid access to the desired compounds under solvent-free conditions at 110 °C following a simple work‐up procedure, and avoids the use of harmful organic solvents. This method therefore represents a significant improvement over the methods currently available for the synthesis of tetrahydrobenzo[a]xanthene-11-ones.