Polar effects in free-radical reactions. The paradox of reduction of alkyliodides 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 f ormed iodoalkanes are reduced back to alkanes by excess t-BuOOH; the rate c onstant for hydrogen abstraction from t-BuOOH by a primary alkyl radical ha s been roughly evaluated to be similar to 10(4) M-1 s(-1). Two new procedur es for the reductive alkylation of alkenes by t-BuOOH and Pb(OAc)(4) are re ported. The importance of the polar effects and the rate constants of the k ey elementary steps involved in these processes is discussed.