Pyridinium salts are valuable building
blocks, which have been
widely applied in various organic transformations during the past
few decades. In particular, N-functionalized pyridinium salts have
been explored as convenient radical precursors, which would go through
reductive single-electron transfer. As a result, the chemistry of
such pyridinium compounds for generating carbon-, nitrogen-, and oxygen-centered
radicals has been witnessed, and a remarkable progress has been achieved,
making it a hot topic over the last five years. This Review describes
recent advances in the area of pyridinium salts as radical precursors,
concerning the development of radical reactions involving pyridinium
salts in organic synthesis.