ZINC OXIDE NANOPARTICLES: AN ENVIRONMENTALLY BENIGN AND REUSABLE CATALYST FOR THE SYNTHESIS OF 1,8-DIOXOOCTAHYDROXANTHENE DERIVATIVES UNDER SOLVENT-FREE CONDITIONS Zinkoxid-Nanopartikeln: AN umweltfreundliche und WIEDERVERWENDBAR Katalysator für die Synthese von 1,8-DIOXOOCTAHYDROXANTHENE Derivate unter l sungsmittelfreien Bedingungen

Zinc oxide nanoparticles (ZnO-NPs) as an environmentally benign and reusable heterogeneous catalysts for the synthesis of series of biologically significant 1,8-dioxo-octahydroxanthene derivatives. This has been accomplished by the condensation of various aldehydes with 5,5- Dimethyl-1,3-cyclohexanedione using ZnO-NPs as an environmentally benign heterogeneous catalyst. ZnO-NPs catalyst exhibited remarkable catalytic activity to achieve the synthetic targets in the range of 80-93% yield under solvent-free condition. ZnO-NPs could be used up to four cycles with similar catalytic response. The protocol provided greater selectivity, cost-efficiency, clean reaction profiles, simple work-up procedure and high yields.