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

Reformatsky reactions of an imine, an α-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 α-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 β-lactam, the corresponding β-aminoester or a mixture of the two products depending on the identity of the imine and α-bromoester.