Studies On The Organic Synthesis Reactions Catalyzed By Solid Acids And Quaternary Ammonium Salt

This thesis consists of two chapters.Chapter one: Studies on the organic synthesis reactions catalyzed by solid acidsIn the first part, silical gel-supported phosphotungstic acid (PTA) is chosen as an efficient catalyst for the acetylation of a variety of alcohols, phenols with acetic anhydride under mild reaction condition. This catalyst is found not to be efficient for the acetylation of tertiary alcohols. As far as phenols are concerned, those which have steric substituents in the aromatic ring require comparatively harsh conditions. This method has some merits such as high yields, simple operation.In the second part, a series of dehydropyrimidin-2-ones are synthesized by the one-pot reactions of aldehydes, p-ketoesters and urea using a catalytic amount of phosphotungstic acid in ethyl alcohols. The modified Biginelli cyclocondensation not only shortens the reactions period and simplifies the operation, but also improves the yields.Chapter two: Studies on the organic synthesis reactions catalyzed by quaternary ammonium saltIn the third part, a general and practical chemistry route to the synthesis of polyfunctionalised benzopyrans using tetrabutylammonium bromide as the catalyst is described. This method provides several advantages such as neutral conditions, high yields and simple work-up procedure. In addition, water is chosen as a green solvent.In the final part, the reaction of an aldehyde, malononitrile and a phenol in water at reflux in the presence of cetyltrimethylammonium bromide as catalyst affords a one-pot synthesis of 2-amino-2-chromenes under ultrasound irradiation. In addition, This method is simple and convenient with minimum environmental impact. Water is chosen as a green solvent.