3‐Alkylidene‐2‐azetidinethiones: Useful Intermediates for the Synthesis of 3‐Substituted 2‐Azetidinethiones

3‐Lithiated 2‐azetidinethiones 1 were allowed to react with carbonyl compounds to give 3‐(1‐hydroxyalkyl)‐2‐azetidinethiones 3, 4 which were converted into α,β‐unsaturated β‐thiolactams 7, 8, 10 by elimination procedures. Alternatively, the title compounds were prepared by Peterson olefination of 3‐trimethylsilyl‐2‐azetidinethiones 9 . Reactions of 7, 8, 10 with thiophenol or sodium diethyl malonate provided the Michael adducts 11 . E/Z Photoisomerization of 7, 8 by visible light was observed. On deprotonation, 7a, 8a underwent allyl rearrangement to 13 .