Recent Developments of Free-Radical Substitutions of Heteroaromatic Bases

Abstract

The most recent mechanistic and synthetic aspects of the substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals are reviewed. From mechanistic point of view the following aspects are discussed; i) Structure-reactivity relationship; ii) Rearomatization of the radical adducts; iii) Solvent and isotope effects; iv) Overlap area with ionic reactions. The synthetic developments concern the following topics: i) Selectivity with carbonyl radicals; ii) Alkyl iodides as sources of alkyl radicals; iii) Alkylation by carboxylic acids; iv) Vinylation by olefins; v) Oxyalkylation by ethers; vi) Catalytic processes; vii) Substitution with strongly nucleophilic radicals.