Studies On The Knoevenagel Reaction And Pinacol Coupling Reaction Under Ultrasonic Irradiation

The applications and development of ultrasound in organic synthesis in recent three decades have been reviewed in this paper. Studies on the Knoevenagel reaction and Pinacol Coupling under ultrasound have been carried out. Partl: Progress in Organic Synthetic Sonochemistry. Ultrasound is used more and more frequently in organic synthesis in recent three decades. Compared with traditional methods, this new method is more convenient and easily controlled. A great many of organic reactions can be carried out in higher yields, shorter time or milder conditions under ultrasonic irradiation. It can even set off some reactions, which can not be carried out under traditional conditions. The applications of ultrasound in organic synthesis in recent years have been reviewed. Part2: Studies on the Knoevenagel reaction and Pmacol Coupling under ultrasound 2.1 Ultrasonic irradiation is found to facilitate the Knoevenagel reaction. Knoevenagel condensation of malonic acid with aromatic aldehydes catalysed by expansive graphite results cinnaniic acids in 65-98% yields under ultrasound irradiation. The reactions are carried out at 41?30C and completed within 3-lOh. 2.2 Condensation of ketones with ethyl cyanoacetate catalysed by ammonium acetate-acetic acid results ethyl alkylidene cL-cyanoacetate in 3 l?-89% yield under ultrasound irradiation at 4l-450C within 3.5-21h. 2.3 The coupling reaction of aromatic carbonyl compounds leading to pinacols was carried out using Zn-ZnCI2 in 50% aqueous THF under ultrasound in 5-77% yield. The reactions were completed within 3h at r.t. 2A The coupling reaction of aromatic carbonyl compounds leading to pinacols was carried out using Znlmontmorillonite K10-ZnCI2 in 50% aqueous TJr{F under ultrasound in 23-87.1% yield. 2.5 The pinacol coupling reaction of aromatic aldehydes and ketones was performed in 8-95% yield with magnesium in 0. 1M aqueous NH4CI. under ultrasound irradiation at rt. in 3h.