Synthesis of Benzyl Ketones through Indium-Mediated Solvent-Free Reaction of Acid Chlorides with Benzyltins under Ultrasound Irradiation

In recent years, the development of indium-mediated synthetic methods has grown up in the literature due to the special properties of indium metal. In this respect, we have established that this metal is a promoter of the solvent-free reaction of acid chlorides with arylstannanes applied to the synthesis of hindered benzophenones and alkyl aryl ketones under ultrasound irradiation. In this work, the reaction of acid chlorides with benzyltributyltin was successfully conducted in the presence of indium powder under solvent-free condition. The corresponding benzyl ketone products were obtained in good to excellent isolated yields (60-85%). Under ultrasonic irradiation the reaction times are significantly reduced from 2-3 h to 10-20 min without affecting yields. We carried out control experiments which showed that no reaction ocurred in the absence of indium, indicating that the metal acts as a promoter for this reaction. Working with dibenzyldibutyltin as substrate it is possible to transfer two benzyl groups from tin, thus improving effective mass yield. Benzyltriphenyltin affored the desired ketone although in moderate yield (45%).