Asymmetric Synthesis of Dihydrocoumarins via Squaramide‐Catalyzed [4 + 2] Annulation Reaction of 2‐Hydroxy α‐Amido Sulfones and Azlactones

An efficient asymmetric organocatalytic [4 + 2] annulation of 2‐hydroxy α ‐amido sulfones with azlactones in the present of a chiral squaramide has been successfully developed. This protocol furnishes a series of enantioenriched multi‐substituted dihydrocoumarin derivatives with high yields (up to 96%), good to excellent stereoselectivities (up to >20:1 dr, 82%–99% ee) under mild reaction conditions. The method has demonstrated a rapid preparation of highly functionalized dihydrocoumarins, which will enrich the field of the catalytic asymmetric reactions of azlactones. Moreover, the large‐scale reaction, straightforward derivatization of chiral products highlight the practical value of this method.