Xanthene derivatives have attracted considerable interest in recent years because of their promising activity as positive allosteric modulators of metabotropic (mGlu) receptors1 and potent nonpeptidic inhibitors of recombinant human calpain I2. These have been used as rigid carbon skeletons for the construction of new chiral bidentate phosphine ligands with potential applications in catalytic processes3. In particular, xanthenediones constitute a structural unit in a number of natural products4 and have been used as versatile synthons because of the inherent reactivity of the inbuilt pyran ring5 as well as synthetic derivatives and occupy a prominent position in medicinal chemistry6.

The synthesis of xanthenediones usually condenses appropriate active methylene carbonyl compounds with aldehydes catalyzed by sulfuric acid or hydrochloric acid7. Vranken et al. 8 described two-step synthesis of 9-aryl-6-hydroxy-3H-xanthen-3-one fluorophores by condensation of aryl aldehydes and fluororesorcinol. Singh et al. 9 reported a new method for the preparation of xanthenediones through carbon transfer reactions of 1, 3-oxazinanes and oxazolidines with carbon nucleophiles.