The consecutive [2+2] cycloaddition-ring expansion route to diastereomeric 1,4-diazepin-5-ones from imino-ketenimines.: Alternative intramolecular transamidation of β-lactams

Azeto[1,2-a]imidazoles are prepared by a formal intramolecular [2 + 2] cycloaddition of imino-ketenimines in which an ethylene chain is linking the nitrogen atoms of both functionalities. bearing a methyl and a phenyl group on the terminal carbon atom of the heterocumulene. By acid-catalyzed hydrolysis these azeto[ 1,2-a]imidazoles are converted into 6.6.7-trisubstituted hexahydro-1.4-diazepin-5-ones, which have been alternatively prepared via intramolecular transamidation of N-(2-aminoethyl)-beta-lactams. (C) 2004 Elsevier Ltd. All rights reserved.