Synthesis and characterization of new enantiopure 7,7 '-disubstituted 2,2 '-dihydroxy-1,1 '-binaphthyls: Useful ligands for the asymmetric allylationreaction of aldehydes

As an extension of our interest in developing new enantioselective reaction s based on the binaphthol privileged ligand, we report a simple approach to the synthesis of 7,7'-disubstituted binaphthols. The commercially availabl e 1,7-dihydroxynaphthalene (1) was used as starting material for the prepar ation of the bromoderivatives 2, which were oxidatively coupled to afford 3 , a key intermediate for the preparation of a variety of enantiopure substi tuted binaphthols (8, 10). The absolute configuration of the new compounds was established by chiroptical analysis and by cholesteric induction. The o ptically active catalysts derived from the ligands 3, 8, 10, 16 and 17, com plexed with Ti(OiPr)2Cl2, Zr(OiPr)4 and ZrC14(THF)2, were employed for the enantioselective addition of allyltributyltin to aldehydes. Finally, the in fluence of the substituent of the binaphthyl core on the transmission of th e chiral information was also investigated.