The reactions of dioxanyl and cyclohexyl radicals with 2-and 3-X-pyridines (X= CN, COMe, CO2Me) give a single substitution product deriving by addition at the 5-and 6-positions respectively; with 4-X-pyridines substitution occurs preferentially at the 3-position. If the reactions are carried out with protonated pyridines other positional isomers are obtained. From the synthetic point of view the two procedures are therefore complementary. The ...
