Studies On The Cyclocondensations Under Ultrasound Irradiation

The applications of ultrasound in organic synthesis in recent years have been reviewed. Studies on the cyclocondensation have been carried out under ultrasound irradiation. This thesis consists of five chapters:Chapter 1: Ultrasound irradiation has increasingly been used in organic synthesis in recent years. Compared with traditional methods, this method is more convenient and easier to be controlled. A large number of organic reactions can be carried out in higher yields, shorter reaction times and milder conditions under ultrasound irradiation. The applications of ultrasound in organic synthesis in recent years have been reviewed inthis paper.Chapter 2: The condensation of aldehydes, festers and urea catalyzed by amidosulfonic acid in anhydrous ethanol results 3, 4-dihydropyrimidin-2-ones in 70-97% under ultrasound irradiation in 25-60 min. The present method has the additional advantages of milder reaction conditions, shorter reaction time, higher yield and easy of work-up.Chapter 3: Under ultrasound irradiation, the condensation of ethyl a-cyanocinnamates with thiourea activated by potassium carbonate at room temperature in ethanol results 4-oxo-2-thiohexahydropyrimidines in 51-98% in 0.5-2.0 h. The advantages of the procedure are short reaction period, high yield and simple work-up. Chapter 4: A series of 2-amino-4-aryl-3-cyano-7, 7-dimethyl-5-oxo-5, 6, 7, 8-tetra-hydro-4H-benzopyran derivatives have successively synthesized by the condensation of arylmethylidenemalononitriles with 5, 5-dimethyl-l, 3-cyclohexanedione without catalyst in DMF under ultrasound irradiation. This method of synthesis of pyran derivatives has the advantages of short reaction time, high yield and simple work-up. Chapter 5: Synthesis of 4-oxo-2-thiohexahydropyrimidines from ethyl 2-cyanopro-penoates with thiourea is carried out in methanol in very good yields with sodium methoxide as catalyst at room temperature. This method for synthesis of 4-oxo-2-thiohexahydropyrimidines is a simple, high yield and timesaving process.