cis and trans-Aryl-2-azetidinone-tethered haloarenes can be stereoselectively prepared using the ketene-imine cyclization. These beta-lactam-tethered haloarenes were used for the regiocontrolled preparation of beta-lactam-biaryl hybrids including fused tetracyclic biaryl-2-azetidinones as well as C4-dearylated not fused biphenyl-2-azetidinones via aryl-aryl radical cyclization and/or rearrangement. Alternatively, trans-dibenzocarbacephems could be stereoselectively prepared, both in racemic and enantiopure form, through the Staudinger reaction between phenanthridine and activated ketenes. (c) 2005 Elsevier Ltd. All rights reserved.