Diastereomeric Resolution of rac-1,1′-Bi-2-naphthol Boronic Acid with a Chiral Boron Ligand and Its Application to Simultaneous Synthesis of (R)- and (S)-3,3′-Disubstituted 1,1′-Bi-2-naphthol Derivatives

Abstract

A new concept of diastereomeric resolution has been developed where a boronic acid functionality was employed as (1) a diastereomeric resolving group with a chiral boron ligand and (2) a masked functional group for further transformation thereafter. This new diastereomeric resolution method was successfully applied to the preparation of both (R)- and (S)-3,3'-disubstituted 1,1'-bi-2-naphthol (BINOL) derivatives in a step-ecomonical manner. Racemic BINOL boronic acid reacted with a commercially available pinene-derived iminodiacetic acid as a chiral boron ligand to generate the two diastereomers in quantitative yields over a gram-scale quantity. After the removal of the chiral boron ligand from the diastereomers under mild conditions, the subsequent Suzuki coupling reaction of the resulting chiral BINOL boronic acids with aryl halides provided a series of both (R)- and (S)-BINOL derivatives in good yields. Further, both resulting diastereomers could be directly applied to the Suzuki coupling reaction without the removal of the chiral ligand.