Chiral Phosphoric Acid Catalyzed Enantioselective Desymmetrization of 1,4‐Dihydropyridines by C(sp3)−H Bromination.

Described herein is the enantioselective synthesis of Hantzsch‐type 1,4‐dihydropyridines (DHPs), which are frequently contained in pharmaceuticals. Readily available symmetrical 1,4‐DHPs were used as substrates, and the methyl group at the 2‐ or 6‐position of the 1,4‐DHP was selectively monobrominated by desymmetrizing enantioselective bromination. The inert C−H bond was converted into a versatile C−Br bond, which guaranteed the modification of the chiral 1,4‐DHP derivatives with high efficiency. Furthermore, axially chiral 4‐aryl pyridines were accessible by central‐to‐axial chirality conversion. [ABSTRACT FROM AUTHOR]