SYNTHESIS OF BETA-LACTAMS VIA CYCLOADDITION OF HYDRAZONES WITH PHENOXYKETENE

Phenoxyketene is capable of annelating the disubstituted hydrazones to afford stereoselectively cis-monocyclic β-lactams with a 1-amino functionality. The ease of cycloaddition is governed by substituents on the azomethine carbon as well as on the hydrazone nitrogen. The 4-disubstituted β-lactams (4a-c and 6a-b) were prepared through the reacion of N,N-diphenylhydrazones and N-methyl-N-phenylhydrazones of ketones with phenoxyacetyl chloride/Et3N in dichloromethane. A similar reaction using aldehyde and ketone hydrazones, derived from N,N-dimethylhydrazine, produced 4-monosubstituted (8a-d) as well as 4-disubstituted (8e-l) β-lactams in good yields. © 1990, American Chemical Society. All rights reserved.