Dual N -Heterocyclic Carbene/Thiourea Catalysis Enabled Asymmetric Dearomative Michael Addition of C ₃ -Fluorooxindoles to 2-Nitrobenzofurans

We report a synergistic dual-catalytic approach that combines a commercially available chiral N-heterocyclic carbene (NHC) with a simple achiral thiourea catalyst to achieve a dearomative Michael addition. This cooperative system enables noncovalent activation modes that promote efficient access to dearomatized 2,3-dihydrobenzofuryl and fluorinated oxindole frameworks. The methodology proceeds in good yields and delivers products with excellent stereocontrol (dr of >20:1 and ee up to >99%). This strategy not only provides a general platform for the synthesis of densely functionalized oxindoles but also highlights the power of synergistic organocatalysis in addressing challenging fluorine-incorporated stereogenic motifs.