2,3-Dioxabicyclo
The photooxygenation of 1,4-cyclohexadiene (3) affords the diastereomeric hydroperoxy endoperoxides exo-4 and endo-4 and the diastereomeric hydroperoxides trans-5 and cis-5 in a ratio of 87:9:3. 5:0.5. Selective reduction of hydroperoxide group in the endoperoxides exo-4 and endo-4 in the presence of titanium tetraisopropoxide-diethyl sulfide gave the corresponding hydroxy endoperoxides exo-7 and endo-7, which on PCC oxidation leads to the phenol-derived keto endoperoxide 2. The triphenylphosphine deoxygenation of the keto endoperoxide 2 produces a 9:1 mixture of 1, 2- and 1,4-dihydroxybenzenes 10 and 11, while the CoTPP-catalyzed rearrangement affords the bisepoxide 12, malealdehyde (13), and beta-lactone 14. The mechanisms of these transformations are presented.