Alkylation of alkenes by radicals generated through photoinduced single electron transfer

Abstract

Irradiation of 1,2,4,5-benzenetetracarbonitrile (TCB) in the presence of several donors (some 2- t-butyl-1,3-dioxolanes, pivalic acid, t-butyltrimethylstannane, t-butyldimethylsilyl n-octyl ether) leads to fragmentation of the donor radical cation to give the t-butyl radical. When the irradiation is carried out in the presence of electron-withdrawing substituted alkenes, the radical is trapped and the adduct radical either couples with TCB -• (the overall process is then radical olefin coupling - aromatic substitution) or is reduced by it (resulting in TCB photosensitized alkene alkylation). The effect of the radical precursor structure and of the medium on these new reaction is discussed.