Polar Effects in Free-Radical Reactions. Selectivity and Reversibility in the Homolytic Benzylation of Protonated Heteroaromatic Bases

The homolytic benzylation of protonated 4-cyanopyridine, quinoline, 2-methyl- and 4-methylquinoline, isoquinoline, and quinoxaline is investigated. The great influence of the polar effect and of the reversibility of the addition of the benzyl radical on the reaction selectivity is discussed. It is put forward the hypothesis that the HSAB principle can be extended to free-radical reactions when the polar effect is the dominant factor. © 1986, American Chemical Society. All rights reserved.