Green synthesis of novel bis(hexahydro-1H-xanthene-1,8(2H)-diones) employing p-toluenesulfonic acid (p-TSA) as a solid acid catalyst

Green synthesis of novel bis(hexahydro-1H-xanthene-1,8(2H)-diones) which are linked to aliphatic or aromatic spacers via ether or ester linkages were performed in good to excellent yields by the reaction of 5,5-dimethyl-1,3-cyclohexanedione with the appropriate bis-aldehydes using p-TSA as an organic acid solid catalyst. The reaction of the bis-aldehydes with barbituric acid or 1,3-dimethylbarbituric acid instead of 5,5-dimethyl-1,3-cyclohexanedione afforded the corresponding Knoevenagel condensation adducts in good yield.