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

Cycloadditions of 6H‐1,3,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α‐pyrones), 13[1].–Diels‐Alder Reactions with 6H‐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.