Recent developments in the Hantzsch synthesis of dihydropyridines

1,4-Dydropyridines are important pyridine-based organic scaffolds which have vast pharmaceutical and synthetic applications. The Hantzsch dihydropyridine synthesis is the most important synthesis to generate 1,4-dihydropyridines. There have been many synthetic advancements reported in the Hantzsch dihydropyridine synthesis. This chapter focuses on the synthetic advances reported in the period 2018–2022, and is based on three-component reactions of an aldehyde, β-ketoester and ammonium salt in the presence of diverse catalysts, including ionic liquids, deep eutectic solvents, heterogeneous catalysts, nanocatalysts and magnetic nanocatalysts. Various catalyst-free water-mediated Hantzsch syntheses, microwave and ultrasound-assisted Hantzsch syntheses, which increase the greenness of the method, are also covered in this chapter.