The thermal isomerization of the title compounds 3a–d to the bicyclic oxadiazines 4a–d becomes increasingly difficult with bridge size n and could not be detected in the case of 3d. The reversibility of the isomerization has been demonstrated for [Formula: see text].Cyclooctadiene behaves both as a diene and as a dienophile in its reaction with azodibenzoyl.
The isomerization of the Diels–Alder adducts of azodiacyls with cyclopentadiene and 1,3-cyclohexadiene is powerfully catalyzed by strong protic acids and by Lewis acids. In adducts from p-substituted azodibenzoyls with cyclopentadiene the catalytic effect increases with electron release by the substituent.
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