| Abstract: | 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 C?C 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. Compounds 3 and 11 reacted with diazomethane to give the highly reactive bicyclic derivatives 8 and 12 , respectively. The cinnamylidene‐lactames 16a,b were converted by selective ozonolysis mainly into the formylmethylene lactames 17a,b (Scheme 3). The amino‐substituted aldehyde 20 bears a structural relationship to the lactone antibiotic basidalin 21a . The tendency of some donor‐substituted maleimides to undergo 2 + 2] cycloadditions was assessed (Scheme 4). The configuration of the photodimers 22a,b and 24a,b was established by X‐ray crystallography. |
