Five-membered ring systems with O and N atoms

This chapter discusses the five-membered ring systems with O & N atoms such as isoxazoles, isoxazolines, isoxazolidines, oxazoles, oxazolines, oxazolidines, and oxadiazoles. Novel reactions, applications as synthetic intermediates or ligands, and synthetic methods of this class of heterocycles published in the calendar year 2021 are reviewed.