Free-radical and electrophilic functionalization of pyrazol-3-ones with C–O or C–N bond formation (microreview)

Pyrazol-3-ones are known as a class of anti-inflammatory drugs and popular heterocycles in search for new bioactive substances. The electrophilic or freeradical functionalization of C-4 position of pyrazolin-3-ones with the formation of C–C, C–S, C–Hal, C–N, and C–O bonds has been extensively developed in the last decade. Among these methods, the C–O or C–N bond forming reactions are studied less. This microreview covers selected examples of such reactions published in the last 10 years.