Synthesis of a C2-symmetric chiral bipyridyldiol ligand and its application in the enantioselective addition of diethylzine to substituted benzaldehydes

Herein the synthesis of a novel C-2-symmetric ligand comprising of a central bipyridine-pinene-derived core and two functionalized diphenylmethanol subunits is described. [8'-(Hydroxy-diphenyl-methyl)-10,10,10',10'-tetramethyl-[5,5']bi[6-aza-tricyclo[7.1.1.0(2,7)]undecyl]-2(7),3,5,2'(7'),3',5'-hexaen-8-yl]-diphenyl-methanol 10 is a suitable catalyst for the enantio selective addition of dialkylzinc to various aromatic aldehydes with asymmetric inductions of up to 99% cc. Importantly, the correlation of Hammett substituent constants and enantiomeric excess, with the electron-donating group at the para-position and the electron-withdrawing group at the meta-position of substituted benzaldehydes were demonstrated to give high enantioselectivity in alkylations using diethylzinc. (C) 2004 Elsevier Ltd. All rights reserved.