Can ultrasound substitute for a phase-transfer catalyst?: Triphase catalysis and sonochemical acceleration in nucleophilic substitution of alkyl halides and α-tosyloxyketones:: synthesis of alkyl azides and α-azidoketone

Alkyl halides and alpha-tosyloxyketones afford the corresponding azide derivatives upon treatment with aqueous sodium azide under triphase catalysis or ultrasound irradiation conditions. The use of surfactant pillared clay materials and sonochemistry has been compared and demonstrated in these nucleophilic substitution reactions. It appears that the use of a two-phase system in conjunction with ultrasound irradiation is the method of choice that precludes the need for a catalyst in such reactions. (C) 1999 Elsevier Science B.V. All rights reserved.