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

Abstract

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.