Polar effects in free-radical reactions. The paradox of reduction of alkyl iodides and reductive alkylation of alkenes by strong oxidants (t- BuOOH, Pb(OAc)4)

Alkanes are directly iodinated by perfluoroalkyl iodides by a free- radical chain process initiated by t-BuOOH in acetic acid solution. The initially formed iodoalkanes are reduced back to alkanes by excess t-BuOOH; the rate constant for hydrogen abstraction from t-BuOOH by a primary alkyl radical has been roughly evaluated to be ~ 104 M-1 s-1. Two new procedures for the reductive alkylation of alkenes by t-BuOOH and Pb(OAc)4 are reported. The importance of the polar effects and the rate constants of the key elementary steps involved in these processes is discussed.