A new type of axially chiral cyclo-[1,1'-biphenyl]-2,2'-diol (CYCNOL) ligands with adjustable dihedral angles have been developed by varying the bridge chain length. Eight-, nine- and ten-membered cyclo-ligands were prepared and evaluated by using two representative examples: enantioselective additions of diethylzinc to aldehydes and organometallic reagents to enones. The results revealed that the fine regulation of dihedral angles through variation of the bridge chain length was effective in the asymmetric synthesis.
Keywords: asymmetric catalysis; asymmetric synthesis; enantioselectivity; ligand design; ligand effects.
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.