Sonochemical bromination of acetophenones using p-toluenesulfonic acid-N-bromosuccinimide

Substituted acetophenones react with N-bromosuccinimide (NBS) and p-toluenesulfonic acid (p-TsOH) in the presence of ultrasound in methanol at 35 +/- 2 degreesC to give alpha -bromoacetophenones in high yield. In the absence of ultrasound the reaction takes place at the boiling point of methanol (65 degreesC) and takes longer time. The reaction does not take place in the absence of p-TsOH thermally or sonically. However the reaction is possible under photochemical conditions in the absence of p-TsOH. The best solvent for the reaction was found to be methanol. (C) 2002 Elsevier Science B.V. All rights reserved.