Selective C-S bond cleavage of a beta-sultam ring was achieved by the reactions with Lewis acids. Aryl ketones or aldehyde were provided from 3-aryl-beta-sultams whereas beta-sultams bearing a poorly migratory substituent at C-3 gave trans-1,2,3-oxathiazolidine 2-oxides and/or cis-aziridines. These reactions were influenced by the cation-stabilizing capability of C-4 substituents and by the configuration of the substituents at C-3 and C-4. Some 4-alkenyl-3-aryl-beta-sultams underwent tandem intramolecular cyclization to give bicyclo[3.2.1]- and [2.2.1]-gamma-sultams via the processes of C-S bond cleavage, 1,2-aryl shift, cation-olefin cyclization and recombination of the sulfonyl anion. (C) 1998 Elsevier Science Ltd. All rights reserved.