Intramolecular nitrilimine cycloadditions onto β-lactams bearing an alkenyl dipolarophile: synthesis of novel tricyclic β-lactams

Abstract

A five-step synthesis of novel tricyclic β-lactams has been exploited by stereoselective intramolecular cycloadditions of appropriate nitrilimines 6 and 12. These labile intermediates were generated in situ from the corresponding hydrazonoyl chlorides giving rise to the hitherto unknown azeto[3′,4′:1,2]hexano[3,4- c]pyrazole and azeto[3′,4′:1,2]heptano[3,4- c]pyrazole skeletons.