3-hydroxypyridones 8/9 (azagrevellins) were prepared by reaction of the pyrrolidinetrione 4 and diazoalkanes. The ring enlargement proceeded by anionotropic [1,2]-rearrangement introducing carbon between C-3 and C-4 or, to a lesser extent, between C-2 and C-3 due to the different migration aptitudes of the two acyl groups involved. In a cognate manner ring expansion between C-2 and C-3 occured by the interaction of
Ozonations of alkoxy- and (acyloxy)-substituted alkylidene-lactams 1 and 5 or of the alkylidene-sultams 9 and 10 proceeded by regioselective cleavage of the exocyclic CC bonds (Schemes 1 and 2). These bonds are part of an enamide system and, therefore, possess considerable polarity as shown by 13C-NMR spectra. As a result, the partly known maleimides 3 and 6 or the ‘sulfonimides’ 11 were obtained.