Asymmetric Synthesis of 3,4‐Dihydroquinolin‐2‐ones via Organocatalytic [4+2]‐Cyclization of 2‐Amino‐β‐nitrostyrenes with Azlactones

Dihydroquinolin‐2‐ones, recognized for their bioactive properties, feature a six‐membered structure with nitrogen‐containing heterocycles. A method has been developed for synthesizing enantioenriched 3,4‐dihydroquinoline‐2‐one derivatives. This approach utilizes an asymmetric [4+2]‐cyclization process, combining 2‐amino‐β‐nitrostyrenes with azlactones, and is facilitated by a bifunctional squaramide‐based organocatalyst. This process has enabled the creation of chiral 3,4‐dihydroquinoline‐2‐ones with complex structures, including chiral tetrasubstituted carbon stereocenters, delivering corresponding products in 26–95% yield with a diastereomeric ratio of 1.2:1–19:1 and 52–97 ee.