Photooxygenation of 5- and 6-chloro-1,3-cycloheptadienes and Reactions of their Endoperoxides with Base: Effects of the Chloro Substituent on the Reactions

Abstract

Photooxygenation reactions of 5- and 6-chlorocycloheptadienes 6 and 7 gave bicyclic endoperoxides 10–13. The endoperoxides 10 and 13 are major products due to the steric effects of the chloro substituent. The reactions of endoperoxide 10 with NEt₃ under different conditions gave 1,4-epoxide 14, hydroxyenone 15, diketone 16, acetates 17–19 and diacetate 20. The reaction of endoperoxide 10 with pyridine and Ac₂O gave diacetate 20 and dienone 21. The reaction of endoperoxide 13 with NEt₃ gave tropone. The effects of the chloro substituent are discussed.