Cycloadditionen von 6 H ‐1,3,4‐Oxadiazin‐6‐onen (4,5‐Diaza‐α‐pyronen), 13 [1] . Diels‐Alder‐Reaktionen mit 6 H ‐1,3,4‐Oxadiazin‐6‐onen als Dienophil

Cycloadditions of 6 H ‐1,3,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α‐pyrones), 13 [1] .–Diels‐Alder Reactions with 6 H ‐1,3,4‐Oxadiazin‐6‐ones as Dienophile 2,5‐Diphenyl‐1,3,4‐oxadiazin‐6‐one ( 1b ) reacted as dienophile with 2,3‐dimethyl‐1,3‐butadiene to afford the pyridooxadiazinone 5 . Analogously, the oxadiazinoisoquinolines 7c– e were formed on treatment of 2‐(4‐nitrophenyl)‐ ( 1c ), 2‐(4‐tolyl)‐ ( 1d ), and 2‐(4‐bromophenyl)‐5‐phenyloxadiazinone ( 1e ) with 1,2‐bis(methylene)cyclohexane ( 6 ). In contrast, the methyl oxophenyloxadiazinecarboxylate 1a gave a low yield of the cyclopentenone derivative 8 and 7a in the ratio 2.3:1.0. A third type of product, i.e. the cyclobutanone derivative 9 , resulted on exposure of the anisyl(isopropyl)oxadiazinone 1f to 6 . The oxadiazinones 1d, e, f have been prepared for the first time. X‐ray structure analyses established the identity of the compounds 7d and 9 .