Asymmetric Synthesis of Dihydrocoumarins via Squaramide‐Catalyzed [4 + 2] Annulation Reaction of 2‐Hydroxy <i>α</i> ‐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.