Catalyst-free sonochemical synthesis of 1,8-dioxo-octahydroxanthene derivatives in carboxy functionalized ionic liquid

An efficient methodology for the synthesis of 1,8-dioxo-octahydroxanthene derivatives under ultrasonic irradiation at room temperature using carboxy functionalized ionic liquid 1-carboxymethyl-3-methylimidazolium tetrafluoroborate, [cmmim][BF4], without any added catalyst, is described. The reaction involves condensation between 5,5-dimethyl-1,3-cyclohexanedione (dimedone) and structurally diversed aldehydes. The resultant products were obtained in excellent isolated yield with high purity. Ionic liquid was recycled and reused with prominent retention in its activity for at least six times.