ZIOC researchers developed a novel method of radical addition to C=N bond
Nucleophilic addition to C-N bond is a common approach to the synthesis of aliphatic amines. However, due to the lower reactivity of imines compared to carbonyl compounds, such processes require the use of highly nucleophilic organometallic reagents, Lewis acids, or imines containing electron-withdrawing groups at the nitrogen atom. A possible way to carry out such transformations is a free radical pathway, but most often this is problematic due to the low tendency of the C=N bond to interact with radicals due to the instability of the resulting N-centered radical.
Scientists from the Laboratory of Functional Organic Compounds of the Zelinsky Institute have proposed a new method for the synthesis of amines by radical addition to a multiple C=N bond. During the reaction, organozinc reagents are generated in situ from alkyl iodides, which successfully react with various imines upon irradiation with visible light in the presence of a photocatalyst. Presumably, the key factor ensuring the efficiency of the process is the coordination of the starting imine with zinc compounds acting as a Lewis acid. As a result of such coordination, radical addition is facilitated and the resulting N-centered radical is stabilized.
Anton A. Gladkov, Vitalij V. Levin, and Alexander D. Dilman Photoredox Promoted Barbier-Type Reaction of Alkyl Iodides with N‑Alkyl and N‑Aryl Imines // J. Org. Chem. 2023, 88, 1260–1269. DOI: 10.1021/acs.joc.2c02598.