Abstract: | On acid-catalyzed hydrolysis, the tricyclic compounds 2 and 10 , incorporating cyclopropyl-silyl-ether moieties undergo rearrangement to the cis-decalones 3 and 7 , respectively. Hydrolysis of 2 and 10 in the presence of oxygen leads additionally to the formation of the 1,2-dioxolan-3-ols 9 and 13 , respectively, which involves an electron-transfer oxygenation process as could be demonstrated by photooxygenation of the silyl ether 10 and the cyclopropanol 14 in the presence of 9,10-dicyanoanthracene. The configurations of 3 and 9 were assigned by X-ray analysis of the latter compound as well as of the p-nitrobenzoate 8 of 3 . |