Ozonolysis of bis-endo-diacylbicyclo[2.2.1]heptenes in dichloromethane–methanol

Ozonolysis of bis-endo-diacylbicyclo[2.2.1]heptenes 3a–d at −78 °C in dichloromethane–methanol gave the hydroperoxides 6a–d in 70–80% yields. Ozonolysis of bis-endo-diacetylbicyclo[2.2.2]octene 15 and bis-endo-diacetyl-7-oxabicyclo-[2.2.1]heptene 16 under the same reaction conditions gave the hydroperoxides 17 and 18, respectively. The intramolecular sequential nucleophilic addition of the carbonyl groups to the carbonyl oxide group was observed for the first time and was found to be faster than the intermolecular nucleophilic addition of a methanol molecule to the carbonyl oxide group. Ozonolysis of compound 23 in CH2Cl2–MeOH at −78 °C followed by reduction with Me2S gave compounds 24 and 25, in which the stereochemistry of the methoxyl groups was determined by X-ray analysis.