Mechanistic Vistas of Trivalent Nitrogen Compound Reduction by Samarium Diiodide

In trivalent nitrogen compounds, the nitrogen lone pair is highly amenable to bind to samarium iodide prior to electron transfer. As SmI2 is more azaphilic than oxophilic, its affinity to the nitrogen lone pair is more pronounced in aza substrates than in the analogous carbonyl compounds. The impact of this binding is very large in terms of reaction rate and at the same time gives rise to unique mechanistic phenomena, which include unusual kinetic rate orders, catalysis by quantum dots, and remote functionalization. Even reduction of nitriles was found to be affected by this coordination to SmI2. This review focuses on the reduction mechanisms of three groups of compounds: imines, azobenzene, and nitriles. The affinity of Samarium(II) to coordinate with trivalent nitrogen leads to a pre‐association complex prior to the electron transfer. This pre‐association turns out to be extremely effective in terms of enhancing the rate of reduction of substrates with trivalent nitrogen in rather unprecedented mechanistic pathway. This minireview describes these intriguing findings.