Synthesis and Characterization of New Enantiopure 7,7′-Disubstituted 2,2′-Dihydroxy-1,1′-binaphthyls: Useful Ligands for the Asymmetric Allylation Reaction of Aldehydes

Abstract

As an extension of our interest in developing new enantioselective reactions based on the binaphthol privileged ligand, we report a simple approach to the synthesis of 7,7′-disubstituted binaphthols. The commercially available 1,7-dihydroxynaphthalene (1) was used as starting material for the preparation of the bromoderivatives 2, which were oxidatively coupled to afford 3, a key intermediate for the preparation of a variety of enantiopure substituted binaphthols (8, 10). The absolute configuration of the new compounds was established by chiroptical analysis and by cholesteric induction. The optically active catalysts derived from the ligands 3, 8, 10, 16 and 17, complexed with Ti(OiPr)2Cl2, Zr(OiPr)4 and ZrCl4(THF)2, were employed for the enantioselective addition of allyltributyltin to aldehydes. Finally, the influence of the substituents of the binaphthyl core on the transmission of the chiral information was also investigated.