Azidopyrrolines

Another new -lactam synthesis proceeds via the hitherto unknown chloro-cyanoketene, obtained by thermolysis of various /8-azidoenones. Hence, when the crotonolactone (160) was refluxed in benzene in the presence of dicyclohexyl-carbodi-imide 88% of the adduct (161) was obtained similarly thermolysis of (160) with ethoxymethylene aniline gave 48% of (162). The reactions are stereospecific, and only one diastereoisomer was obtained. Thermolysis of 4-azidopyrrolin-3-one (163) in benzene gave 58% of the j8-lactam (165) directly, the zwitterion (164) being implicated without direct evidence such intermediates have already been proposed as precursors of jS-lactams when ketenes add to imines. The f -stereo-... 

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