Light-Mediated Radical Addition to Azomethine Compounds: Novel Reactivity and Activation Modes

Azomethines is a class of compounds, which have traditionally served as electrophilic substrates, but their reactions with radicals have long been limited. Photocatalysis provided ample opportunities for promoting these reactions, with wide variety of reagents serving as precursors of radicals. Besides regular addition mode at the azomethine fragment, the oxidative pathway, in which the C=N bond remains in the product, has become possible by proper selection of redox catalyst. This review summarizes new developments in this rapidly developing field over the past five years. New concepts on activation of the C=N bond towards radical attack are discussed.