HALOGENATED KETENES .9. KETENE CARBODIIMIDE CYCLOADDITIONS

The cycloaddition of various types of ketenes with dicyclohexyl- and diisopropylcarbodiimides to produce imino-β-lactams has been investigated. A large difference in the ketene reactivities was found. The ketenes studied include fluoro-, chloro-, dibromo-, methylchloro-, phenylchloro-, diphenyl-, phenylethyl-, butylethyl-, and dimethylketenes as well as ketene itself. The mechanism of this reaction is discussed in terms of a dipolar intermediate. The preparation of phenylethyl- and phenylchloroketenes and cycloaddition of the latter with cyclopentadiene are also described. © 1969, American Chemical Society. All rights reserved.