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.