Ozonolyses of 1,2-diphenyl- and 2-phenylindene

Ozonolyses of 1,2-diphenylindene (7), 2-phenylindene (18), and the structurally related acyclic keto olefins 13, 14, 26, and 32 were conducted in MeOH/CH₂Cl₂ at -70 and 0°C. The structure of the indenes, 7 and 18, and the reaction temperature, were found to exert an influence on the outcome of the reaction. Ozonolysis of 1,2-diphenylindene (7) at-70°C proceeded exclusively via the carbonyl oxide intermediate 15 providing the methanol-derived isochromen 9a as the sole isolable product. In contrast, four methanol-derived products, 20-23, were obtained from 2-phenylindene (18) under similar reaction conditions, suggesting that the primary ozonide 25 from 18 undergoes two competing modes of decomposition. Ozonolyses of indenes, 7 and 18, and 0°C gave mainly the corresponding ozonides, 8 and 19, respectively, while analogous reactions at -70°C resulted in the predominant formation of the methanol-derived products 9 and 20-23, respectively. The major differences in composition between the ozonolysis product mixtures derived from the acyclic keto olefins 13, 14, 26, and 32 and the appropriate corresponding indenes 7 and 18 suggest that the intermediate carbonyl oxides generated from the former do not make significant contributions to the reaction pathways of the latter. © 1993 American Chemical Society.