Issue in Honor of Prof. Berhanu Abegaz ARKIVOC 2007 (ix) 80-90 ISSN 1424-6376 Page 80 © ARKAT USA, Inc. Synthesis and antimicrobial activity of new 2-azetidinones from N-(salicylidene)amines and 2-diazo-1,2-diarylethanones Girija S. Singh*, Elbert Mbukwa, and Tshepo Pheko Department of Chemistry, University of Botswana, Private Bag 0022, Gaborone, Botswana E-mail: singhgs@mopipi.ub.bw Dedicated to Professor Berhanu M. Abegaz on the occasion of his 60 th birthday Abstract This paper describes the reactions of N-salicylideneamines with diarylketenes generated from thermal decomposition of the 2-diazo-1,2-diarylethanones. An equimolar reaction of the N- salicylidenebenzhydrylamine with diphenylketene affords a mixture of 2- [(benzhydrylimino)methyl]phenyl-2,2-diphenylacetate as a major product and 1-benzhydryl-3,3- diphenyl-4-[2’-(O-diphenylacyl)hydroxyphenyl]-2-azetidinone as a minor product. The reactions of various N-salicylideneamines with 2.2 molar equivalents of 2-diazo-1,2-diarylethanones have been carried out to afford 1-substituted-3,3-diaryl-4-[2’-(O-diarylacyl)hydroxyphenyl]-2- azetidinones as sole product in excellent yields. The products, characterized on the basis of satisfactory analytical and spectral data, have shown moderate to good antimicrobial activity against some bacteria and fungi. Among the fourteen compounds in the series, the 2-azetidinone 4l with a 4-chlorophenyl group on β-lactam ring nitrogen and 4-methylphenyl groups on β- lactam ring C-3 position is the most active compound. Keywords: 2-Azetidinones, diarylketenes, iminophenols, cycloaddition, antimicrobial Introduction 2-Azetidinones, commonly known as β-lactams, are well-known heterocyclic compounds among the organic and medicinal chemists. 1 The activity of the famous antibiotics such as penicillins, cephalosporins and carbapenems are attributed to the presence of 2-azetidinone ring in them. Recently, some other types of biological activity besides the antibacterial activity have been reported in compounds containing 2-azetidinone ring. 2,3 Such biological activities include antifungal, antitubercular, antitumor, cholesterol absorption inhibition and enzyme inhibition activity. The β-lactams also serve as synthons for many biologically important classes of organic