Organocatalytic Asymmetric Oxa‐[3+3]‐annulation for Chiral Tricyclic Chromans with Contiguous Stereocenters

Comprehensive Summary A bifunctional squaramide‐catalyzed asymmetric synthesis of chiral tricyclic chromans bearing three contiguous stereocenters is developed. This strategy leverages synergistic activation between 3‐aminophenol derivatives and 4‐benzylidenepyrrolidine‐2,3‐diones to enable an oxa‐[3+3]‐annulation. The reaction achieves broad substrate scope (34 examples), good yields (64%–81%), excellent enantioselectivity (up to 99% ee), and tunable diastereoselectivity ( dr up to 15 : 1), where chloro‐substituents dramatically enhance stereo‐control. Gram‐scale synthesis and derivatizations confirm practicality. This method provides a versatile platform for complex chroman architectures.