In these studies, it was postulated that the initially formed zwitterionic adducts were stabilized via charge delocalization due to the aromatic substituents at the 2 positi~ n,~ and hence discouraged from ring closure to give 0-lactam-containing products, but not from further reaction with the dichloroketene. In order to prevent delocalized zwitterion formation, thus hopefully encouraging P-lactam formation, the reactions of dichloroketene with 2- ...
