Evidence for an umpolung type of [2+2] cycloaddition of 2-carbamoyl ketenes†
Abstract
Ketenes generated during the thermal decomposition of 5-[(N-aryl/alkylamino)(hydroxyl)methylene]-2,2-dimethyl-1,3-dioxa-4,6-diones react with highly electrophilic iminium ions. The initial [2+2] cycloaddition product rearranges to 2-arylidene malonamide. Mechanistic aspects of the process are presented.