Progress of Metal-Free Visible-Light-Driven α-C-H Functionalization of Tertiary Amines: A Decade Journey

This review article gives an update on the metal-free photocatalyzed and photocatalyzed-free alpha-C-H functionalizations of tertiary amines promoted by visible light. C-H activation is one of the easiest and step-economic strategies to functionalize the alpha-C-H bond of tertiary amines. Various important nitrogen heterocycles having biological significance can be synthesized using alpha-C-H functionalization of tertiary amines. In addition to thermal reactions, many such reactions have been reported using visible light as it is abundant, renewable and green alternative for organic transformations. However, the high price of transition metal photocatalyst prevents its use. In contrast, organic photocatalysts are inexpensive, environment friendly and easy to handle. Therefore, visible-light-promoted metal-free photoredox catalysis (or photocatalyst-free reactions) is being used recently. Although several research articles have been published in this area, no review articles have been reported recently. Here, we have discussed the reactions from the year 2011 to till date with concise discussion about their plausible mechanisms. We believe that the content of this review will guide the readers to develop more such visible-light-promoted reactions using metal-free photocatalysts or avoiding catalysts if possible.