Recent advances in the transformation of nitriles into diverse N-heterocycles

Nitriles, as valuable compounds characterized by carbon-nitrogen triple bonds, represent an important class of synthons in organic synthetic chemistry and materials science. Over the past two decades, the conversion of nitriles to diverse N-heterocycles has attracted significant attention among chemists, owing to its numerous synthetic and economic advantages. Three main types of reactions involving nitriles in N-heterocycle synthesis have been reported, including nucleophilic addition, electrophilic addition and radical addition reactions. In this review, a comprehensive overview of recent progress in nitrile cyclization chemistry is presented. This review is organized and discussed based on the transition metal-catalyzed and metal-free induced N-heterocycle synthesis by C-C, C-N and N-N bond formation reactions using nitriles as nitrogen sources, with an emphasis on the reaction development, mechanisms and subsequent applications of these reactions.