Recent Advances in Synthesis of Chiral 1,2-Dihydropyridines

Chiral 1,2-dihydropyridines represent a class of versatile building blocks that can undergo diversifying reactions of conjugated dienes such as reduction or cycloaddition reaction, allowing facile synthesis of chiral piperidines and other nitrogen-containing heterocycles, prominent structural motifs in drugs and bioactive compounds.The efficient synthesis of chiral 1,2-dihydropyridines is highly desirable and beneficial for the drug discovery and development.The chiral pool strategy and chiral auxiliary based synthesis require the use of stoichiometric chiral reagents, so it is much sought-after to develop catalytic asymmetric methods to synthesize structurally diverse chiral 1,2-dihydropyridines. Since the pioneering catalytic enantioselective addition of nucleophiles to the C2 position of achiral activated pyridine derivatives in 2004, this strategy has been successfully employed for the catalytic synthesis of optically active 1,2-dihydropyridines bearing an aryl, alkyl or alkynyl group at the C2 position.Recently, tandem sequences was reported based on the asymmetric conversion of C＝N bonds as an emerging strategy for the synthesis of multisubstituted chiral 1,2-dihydropyridines.This review summarizes the advances in this field, and discusses the challenges and synthetic opportunities for future development.