Iminium and azonium-activated metal and oxidant-free C-H functionalization of aliphatic amines

A wide variety of synthetic methods have been developed for the synthesis of functionalized aliphatic amines because of their broad utility in both synthetic and medicinal chemistry. The synthesis of functionalized aliphatic amines via direct C-H functionalization of readily available aliphatic amines, the majority of which rely on the use of metallic reagents/catalysts and hazardous oxidants, is advantageous in comparison to the classical multistep approaches. However, the scope to carry out such direct C-H functionalization of aliphatic amines under metal and oxidant-free conditions is being continuously explored. As a result, the examples of C-H functionalization of aliphatic amines employing iminium/azonium ions, which are formed via classical condensation of amines and carbonyl/nitroso compounds, are on the rise. This article summarizes the recent developments in the iminium and azonium-activated metal and oxidant-free C-H functionalization of aliphatic amines with the main focus on the intermolecular reactions of iminium/azonium ions, enamines, and zwitterions with suitable nucleophiles, electrophiles and dipolarophiles.