Halogenated Ketenes. 38. Cycloaddition of α,β-Unsaturated Imines with Ketenes To Yield Both β- and δ-Lactams

Article abstract of DOI:10.1021/jo00163a014

The cycloaddition of various types of α,β-unsaturated imines with diphenyl- and dichloroketenes yields both (2 + 2) and (4 + 2) cycloaddition products, i. e., β-lactams and δ-lactams, respectively.The cycloaddition products are dependent upon substitution in the imine and the ketene.The δ-lactams derived from dichloroketene are easily dehydrochlorinated to the corresponding 2-pyridones.All of the results are consistent with a two-step cycloaddition process involving a dipolar intermediate.