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Note | Regular issue | Vol 68, No. 4, 2006, pp.749-762
Published online, 10th March, 2006
DOI: 10.3987/COM-04-10299
An Unusual Lewis Acid Promoted Isomerization of trans-3-Halo-3-phenylthio-β-lactams

Shamsher S. Bari,* Paloth Venugopalan, Renu Arora, Garima Modi, and Sachin Madan

*Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh-160014, India

Abstract

A method for C-3 epimerization of 3-halo-3-phenylthio-β-lactams, mediated by Lewis acids, is described. TiCl4 promotes isomerization of trans-3-chloro-3-phenylthioazetidin-2-ones (2) to cis-3-chloro-3-phenylthioazetidin-2-ones (3). TiBr4 promotes isomerization as well as substitution of chlorine with bromine affording isomeric cis- and trans-3-bromo-3-phenylthioazetidin-2-ones (5) and (6) respectively, while TiI4 is ineffective.