Recent advances in the chemistry of Katritzky salts as nitrogen-centered radical precursors

The radical intermediates play a significant role in a variety of reactions, enabling rapid access to drug molecules, natural products, building blocks and other functional molecules. While the radicals of Katritzky salts can be generated under the catalysis of transition metal, photoredox, etc, which makes the Katritzky salts involving N—N bond be important precursors of generating nitrogencentered radicals. Here, the brief review has focused on the transformations of nitrogen-centered radical generated from Katritzky salts, reviewing the strategies such as transition-metal catalysis, photoredox catalysis and applications in C—H bond functionalization, difunctionalization of alkenes and alkynes, and other relevant reactions. It is obvious that, Katritzky salts, as important precursors of nitrogencentered radicals, hold the promise of achieving a variety of radical-based transformations for accessing unexplored chemical space.