Hexahydropyrrolo[2,3‐b]indoles: A New Class of Structurally Rigid Tricyclic Skeleton for Oxazaborolidine‐Catalyzed Asymmetric Borane Reduction

A new class of structurally rigid tricyclic chiral ligands based on the hexahydropyrrolo[2,3‐b]indole skeleton has been rationally designed and the catalytic abilities in asymmetric catalysis have been shown in the enantioselective borane reduction of prochiral ketones to afford the chiral alcohols in excellent yields and high enantioselectivities (up to 97% ee).