The　photochemical　oxidation　of　N,N-Bis-(tert-butoxycarbonyl)-1,4-dihydropyrazines　was　investigated　by　irradiation　using　a　medium-pressure　mercury　lamp.　The　main　products　were　isolated,　and　their　structures　were　determined　by　spectral　methods　and　single　crystal　X-ray　diffraction　analysis.　Photooxygenation　is　suggested　to　be　a　[2+2]　cycloaddition　reaction　of　oxygen　to　the　double　bond.