A new synthetic approach to novel spiro-β-lactams

An operationally simple and efficient approach for the synthesis of novel spiro-beta-lactams is described. The key reaction is a halogen-mediated intrasulfenyl cyclization of a cis-3-benzylthio-3-(prop-2-ynyloxy/-enyloxy)-beta-lactam procured through a Lewis acid-mediated C-3-alkylation of the trans-3-benzylthio-3-chloro-beta-lactam carbocation equivalent. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).