An unexpected bicyclic pyrrolidinedione by rearrangement of the β-lactam ring under basic conditions

Abstract

During synthetic studies on anti-elastase polycyclic β-lactams from conveniently substituted monolactams, we attempted to obtain an N-(1´-methoxycarbonyalkylidene)-β-lactam by α-selenoxide elimination. Although the desired alkenes 5 were obtained, the main products were the N-unsubstituted 2-azetidinone 2 and the bridged bicyclic pyrrolidinedione 7. The structure of compound 7 was established by spectroscopic methods and confirmed by X-ray crystallography.