Ag. Griesbeck et T. Deufel, 7A-HYDROXY-1,4,5,6,7,7A-HEXAHYDRO-2H-INDEN-2-ONES BY RING ENLARGEMENTAND SUBSEQUENT PHOTOOXYGENATION OF 1,2-DIHYDROPENTALENES, Synlett, (7), 1993, pp. 467-468
1,2-Dihydropentalenes are converted into the title compounds by a four
-step synthesis involving highly diastereoselective cyclopropanation a
nd singlet oxygen photooxygenation steps.