β-Lactams bearing a Ph2CF substituent at the C(4)-atom were synthesized from N-alkyl-2-fluoro-3,3-diphenylaziridines. The transformation was realized using SbF3-mediated isomerization of the monofluoroaziridines to fluorinated aldimines, followed by Staudinger reaction with ketenes. It was shown that this reaction sequence can be performed as a one-pot procedure. © 2006 Elsevier B.V. All rights reserved.