PHOTOCHEMISTRY OF CIS-AND TRANS-BICYCLO[6.1.0]NONAN-2-ONES

The photochemical behavior of cis- and trans-bicyclo[6.1.0]nonan-2-ones has been found to differ significantly and to be quite solvent dependent. The cis isomer (1) was seen to undergo photoreduction in diethyl ether solution to give cyclononanone and 3-methylcyclooctanone in a ratio of 2:1. In sharp contrast, irradiation of 1 in t-butyl alcohol afforded 4,8-nonadienal, 2-(4-pentenyl)cyclopropanecarboxaldehyde, and trans-bicyclo[6.1.0]nonan-2-one (2). The structures of these products were established by chemical correlations. The photolysis of 2 in ether slowly gave rise to polymer; no volatile product was seen. In t-butyl alcohol solution, however, t-butyl trans-2-(n-pentyl)cyclopropanecarboxylate was produced in 50% yield. Attempts were made to determine the multiplicities of these photochemical transformations and the results are summarized. The possible role of gepmetric and conformational factors in controlling the differing excited state behavior of 1 and 2, the simplest known pair of geometrically isomeric bicyclo[n.1.0]alkan-2-ones, is discussed. © 1969, American Chemical Society. All rights reserved.