RADICAL IONS IN PHOTOCHEMISTRY .9. REACTIONS OF THE 1,1,2,2-TETRAPHENYLCYCLOPROPANE RADICAL CATION

The photosensitized (electron transfer) reactions of cyclo-propanes are particularly interesting because of the unusual intermediates, 1, 3 radical ions, that are involved. The direct irradiation of 1, 1, 2, 2-tetraphenylcyclopropane (I) leads to ring fragmentation to give 1, 1-diphenylethylene and products derived from diphenylcarbene. 2 In contrast, we find that the sensitized (electron transfer) irradiation of I, using 1-cyano-naphthalene (IIIa) or 1, 4-dicyanonaphthalene (IlIb) as electron-accepting sensitizers, gives good yields of the ring-cleaved product, 1, 1, 3, 3-tetraphenylpropene3 (II) (reaction 1). © 1979, American Chemical Society. All rights reserved.