Carbon Nanotube-Supported Butyl 1-Sulfonic Acid Groups as a Novel and Environmentally Compatible Catalyst for the Synthesis of 1,8-Dioxo-octahydroxanthenes

A novel multiwalled carbon nanotube catalyst with -SO3H functional groups was easily prepared from its starting materials and used as an efficient heterogeneous catalyst for one-pot Knoevenagel condensation, Michael addition, and cyclodehydration of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) with various aromatic aldehydes. Using this method 1,8-dioxo-octahydroxanthenes were obtained in excellent yields at room temperature. The present method is superior in terms of reaction temperature, reaction time, easy work-up, high yields, and ease of recovery of catalyst.