Homolytic Alkylation of Protonated Heteroaromatic Bases by Alkyl Iodides, Hydrogen Peroxide, and Dimethyl Sulfoxide

A new general process of selective, homolytic alkylation of heteroaromatic bases of great synthetic interest is described. It is based on the reaction of alkyl iodides with hydrogen peroxide and heterocyclic compounds in DMSO, catalyzed by an Fe(II) salt. It is shown that the iodine abstraction from the alkyl iodide by the methyl radical, generated from the solvent, is the key point of the overall process. Combined enthalpic and polar effects contribute to the high selectivity: the enthalpic factor governs the equilibria of the iodine abstraction, and the polar factor determines the reactivity toward the protonated heterocyclic ring.