CYCLOADDITION OF (N-ALKYL-N-PHENYLAMINO)KETENE WITH IMINES

(N-Alkyl-N-phenylamino)ketenes were prepared in the presence of various imines, and a [2 + 2] cycloaddition reaction occurred to yield 3-(N-alkyl-N-phenylamino)-2-azetidinones. The size and electronic nature of the imine substituents were varied in order to probe those factors that influence the stereochemistry of the cycloaddition. The stereochemistry of the 2-azetidinone was determined by the substitution pattern of the imines. In general, the stereochemistry of the 2-azetidinone products are significantly influenced by the bulk of the N substituent on the imine. These results are discussed in terms of a two-step zwitterionic intermediate.