Synthesis of β-lactams and β-aminoesters via high intensity ultrasound-promoted Reformatsky reactions

Reformatsky reactions of an imine, an alpha-bromoester, zinc dust and a catalytic amount of iodine in dioxane under high intensity ultrasound (HIU) irradiation from an ultrasonic probe are explored. A series of 16 aldimines with varying electronic demands is evaluated as potential electrophiles for reactions with three alpha-bromoesters of differing steric demands. This HIU method is successful for both enolizable and non-enolizable imines affording in short reaction times high yields of a beta-lactam, the corresponding beta-aminoester or a mixture of the two products depending on the identity of the imine and alpha-bromoester. (C) 2004 Elsevier Ltd. All rights reserved.