A Chiral Iron Disulfonate Catalyst for the Enantioselective Synthesis of 2-Amino-2′-hydroxy-1,1′-binaphthyls (NOBINs)

A novel type of chiral redox disulfonate iron complex for asymmetric catalysis is reported. The [Fe((Ra)-BINSate)]+ (BINSate = 1,1′-binaphthalene-2,2′-disulfonate) complex effectively promotes the enantioselective oxidative cross-coupling between 2-naphthols (1) and 2-aminonaphthalene derivatives (2), affording optically enriched (Ra)-2-amino-2′-hydroxy-1,1′-binaphthyls (NOBINs) with exceptional yields and enantioselective ratios (up to 99% yield and 96:4 er). The [Fe((Ra)-BINSate)]+ catalyst was designed as a chiral version of FeCl3 with multicoordination sites available for binding the two coupling partners 1 and 2 as well as the oxidant. Our structure–selectivity and activity study, which covered most of the important positions in the NOBIN scaffold, revealed the effect of different substitution patterns on the coupling efficiency and stereoselectivity.