The cycloaddition of various types of a./J-unsaturated imines with diphenyl-and dichloroketenes yields both (2 + 2) and (4 + 2) cycloaddition products, i.e., /3-lactams and -lactams, respectively. The cycloaddition products are dependent upon substitution in the imine and the ketene. The -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.

Natriumsulfid spaltet die Diarylsulfide (I) zu den Thiophenolen (II).

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