Development of Eagle‐Shaped BPE/Phe‐2NO Ligands: Switch of Enantioselectivity in Friedel–Crafts Alkylation

Abstract The development of single chiral source‐derived ligands to fine‐switch enantioselectivity has been a key aspect in asymmetric catalysis. Herein, in this study, using the same chiral source l ‐prolinamide as the starting material, we synthesize 14 new diphenyl ether bridged C 2 ‐symmetric rigid chiral tertiary amine‐derived dioxide ligands (abberviated as BPE‐2NO) and 9 new m ‐phenylene bridged C 2 ‐symmetric rigid chiral tertiary amine‐derived dioxide ligands (abberviated as Phe‐2NO); their effectiveness was demonstrated in the first switch of enantioselectivity in palladium(II)‐catalyzed Friedel–Crafts alkylation. In the presence of palladium acetate as the Lewis acid, both enantiomers of indole derivatives can be prepared in good‐to‐excellent yields and enantioselectivities by using the single chiral source‐derived Eagle‐shaped BPE/Phe‐2NO ligands. Control experiments and density functional theory calculations provide a rational explanation for the above observations. This study was the first switch of enantioselectivity in palladium(II)‐catalyzed Friedel–Crafts alkylation by using the single chiral source‐derived ligands.