摘要:
The radical cations of 2,2-dialkyl- and 2-alkyl-2-aryl-1,3-dioxolanes, when generated in solution by photoinduced electron transfer to 1,2,4,5-benzenetetracarbonitrile (TCB), fragment to yield alkyl radicals. These are trapped by electron-withdrawing substituted alkenes (acrylonitrile, methyl acrylate, methyl vinyl ketone, as well as dimethyl maleate and fumarate). The radicals thus formed are either reduced by the TCB radical anion or add to it. In the first process (observed only with the diesters) the end result is reductive alkylation of the olefin, while the latter process results in an addition to the olefin-aromatic substitution reaction, The selectivity of the process is explained on the basis of steric hindrance, since the radicals react when still in the cage with the aromatic radical anion.