Application of 2-Aminopyridines in the Synthesis of Five- and Six-Membered Azaheterocycles

Aminopyridine is a significant synthetic synthon, with unique dual nucleophilic structure. It can react with ketones, aldehydes, acids, multifunctional esters, halogenated aromatics and other compounds to synthesize five- and six-member azaheterocycles. In recent years, the cyclization reactions based on 2-aminopyridines have been under the spotlight. According to the different types of substrates, the research progress on the synthesis of imidazo[1,2-a]pyridines and pyrido[1,2-a]pyrimidines based on 2-aminopyridines in the past 5 years is reviewed, and its applications in manic synthesis methodology, drug synthesis and fluorescent probes are summarized. Furthermore, the development trend of green cyclization and its application based on 2-aminopyridines in the future are prospected.