The Reactions Catalyzed By Montmorillonite In Organic Synthesis

Pollutions, especially caused by chemical industry, have become a severe problem in recent years. In order to resolve the problem, chemists have been making great efforts to achieve the environmental friendly synthesis. Montmorillonite has attracted much attention for realize this purpose due to its unique acidity, high activity and efficiency as an organic reaction catalyst.In the last two decades the sonochemical methods as a special technique have been widely used in organic synthesis. Compared with traditional synthetic methods, this method is of the advantages of shorter reaction time, milder conditions, and convenient and easily operation and control. A large number of organic reactions can be carried out in a higher yield under ultrasound irradiation. The interesting results prompt us to develop an environmental friendly method of the organic synthesis on the basis of the combination of using the solid Lewis acids catalysts and microwave irradiation.In this paper the application of Montmorillonite as a solid Lewis acid catalyst in organic synthesis was firstly reviewed. Some organic reactions, such as Knoevenagel condensation and oxidation, catalyzed by Montmorillonite-supported Lewis acids were investigated. In addition, the synthesis of C-glycosides based on 1,3-dipolar cycloaddition was studied.Montmorillonite K10-supported ZnCl₂ has been found to be an efficient and environmentally friendly catalyst for organic reaction. We firstly studied Knoevenagel condensation of malononitrile with aromatic aldehydes catalyzed by Montmorillonite K10-ZnCl₂ under ultrasound irradiation to synthesize arylmethylenemalononitrile. The reaction could complete within 2-10 min in anhydrous ethanol under ultrasound irradiation and afforded arylmethylenemalononitriles in 87-98% yield. It was found that the catalyst can be reused two times without significant decrease in activity.The oxidation of 2-hydroxy-1,2-diaryl-ethanone by FeCl₃/Montmorillonite K10 under microwave irradiation to give 1, 2-diaryl-1, 2-ethanedione was studied. The reaction underwent smoothly with excellent yields and had the advantages of short reaction time,...