A greener synthesis of 1,8-dioxo-octahydroxanthene derivatives under ultrasound

The ceric ammonium nitrate (CAN) has been identified as an efficient and eco-friendly catalyst for the one pot and virtually three-component reaction of 5,5-dimethyl-1,3-cyclohexanedione with various aldehydes in 2-propanol. Under ultrasound irradiation, the reaction proceeded smoothly at a faster rate at 50 degrees C affording a variety of 9-alkyl/aryl/heteroaryl substituted 3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-diones in good to excellent yields. A probable mechanism for this CAN-mediated synthesis of 1,8-dioxo-octahydroxanthene derivatives is presented. Overall, the methodology provides advantages such as low cost, high yields of products and simple operational procedures and is free from the use of harmful chlorinated solvents. (C) 2012 Elsevier Ltd. All rights reserved.