The Diels-Alder reaction is an important and widely used reaction in organic synthesis and in the chemical industry. Rate enhancement of this reaction has been achieved by the use of Lewis acids such as La(OTf)3,1 5 M LiClO4 in Et2O,2 solvents such as water,3 supercritical CO2,4 and ionic solvent,5 and under high pressure,6 or radiation of microwave7 and ultrasound.8 Solid acids such as zeolite,9 clay,10 and alumina11 also accelerate the reaction. From a ...