Efficient one pot synthesis of 1,8-dioxo-octahydroxanthene derivatives using ZnAl2O4 nanoparticles as a catalyst

1,8-dioxo-octahydroxanthenes are important class of oxygen heterocycles in which a phenyl substituted pyran ring is fused on either side with two cyclohexanone rings. Presence of conjugated bis-dienone functionality makes these compounds sensitive to be attacked by nucleophiles and light energy. In the past decade, synthesis of xanthenes derivatives has been of considerable interest to organic chemists because they possess various biological and pharmaceuticals activities such as antiviral, antibacterial and anti-inflammatory properties. These are being utilized as antagonists for paralyzing action of zoxazolamine and in photodynamic therapy [1,2]. Xanthenes and benzoxanthenes derivatives are the parent frame works found in a large number of naturally occurring as well as synthetic products possessing prominent position in medicinal chemistry. Xanthenediones are likewise special structural units constituting various natural products and being used as versatile synthons, because of inherent reactivity of their inbuilt pyran ring [3,4]. In this work, 1,8-Dioxo-octahydroxanthenes have efficiently been synthesized from dimedone and aromatic aldehydes using ZnAl2O4 spinel nanoparticles as a heterogeneous catalyst in ethanol media (scheme 1). The experimental procedure is very simple and the products are formed in high yields.