Photoinduced substitution of 1,3,5-tricyanobenzene by toluene

Abstract

Irradiation of a solution of 1,3,5-tricyanobenzene in acetonitrile in the presence of toluene gives 1-benzyl-3,5-dicyanobenzene and 1-benzyl-3,5,6-tricyanobenzene. In a toluene solution only bibenzyl is obtained. On the basis of results obtained using [²H₈]toluene (i.e. deuterium incorporation only in the benzyl and not in the cyanoaromatic moiety) a series of reactions which involves photoinduced electron-transfer, removal of proton from the radical cation, and then coupling of the radical anion and the radical formed is postulated. It is also suggested that for the coupling reaction to take place then the reduction potential for radical anion to dianion on the cyanoaromatic species might play an important role.