Electron-transfer induced rearrangements of spirofluorene- bicyclo[6.1.0] nonatriene to spirofluorene barbaralane.

The photosensitized irradiation of spirofluorene bicyclo[6. 1.0] nonatriene (1a, R-R=o-C sub 6 H sub 4 -o-C sub 6 H sub 4) leads to the formation of spirofluorenebarbaralane (2a) whereas that of the 9,9-diphenyl derivative yields 7-(beta,beta- diphenylethenyl) cycloheptatriene (3b). These rearrangements are interpreted as radical ion pair reactions.