Photo-oxygenations of 1H-azepine derivatives isolation and characterization of the [6+2] cycloaddition product

The reactions of 1H-azepine derivatives ($\text{1a-b}$ and $\text{4}$) with singlet oxygen gave the 6+2] cycloadducts ($\text{2a-b}$) and the 4+2] cycloadducts ($\text{3a-b}$ and $\text{5}$). The thermal and base-catalyzed rearrangements of the oxygen-adducts were investigated.