A green protocol for catalyst-free synthesis of 1-oxo-hexahydroxanthenes in aqueous medium

An efficient and eco-friendly synthesis of 1-oxo-hexahydroxanthenes has been expediently accomplished by a reaction of salicylaldehyde with cyclohexane-1,3-dione or dimedone in water as universal solvent at reflux condition without a catalyst. Excellent yields of the products, operational simplicity, simple work-up and catalyst-free synthesis are attractive features of this green protocol.