The reactions of lH-azepine derivatives (la_b and 2) with singlet oxygen gave the [6+2] cycloadducts (2a_b) and the [4+2] cycloadducts (3a_b and 5). The thermal and base-catalyzed rearrangements of the oxygen-adducts were investigated. The manifold aspects related to the photo-oxygenation of carbocyclic and heterocyclic polyenes have been extensively investigated. 2) Then, the reactions of singlet oxygen with cyclic polyenes might be expected to give the cycloaddition products in several manners because of the low activation barrier for cycloaddition process. 3) For example, cycloheptatrienes produce the four types of adducts with singlet oxygen, 4) whereas heteroepins such as azepine, 1,2-diazepine and 1,3-oxazepine are known to give the [4+2] cycloadducts as the sole productwith singlet oxygen.5'6) Thus, we re-investigated the photo-oxygenation reaction of N-alkoxycarbonyl lH-azepine (l_) and found the formations of hither-to unknown [6+2] cycloadducts (& and 5) in addition to the [4+2] adducts (3a-b). Furthermore, the reaction of the 3,6-di-t-butyl derivative (4) with singlet oxygen was studied for the comparative purpose with that of tetracyanoethylene (TCNE),