Synthesis of Axially Dissymmetric Ligands with Two Chiral Centers of Perfluoroalkyl Carbinol Moiety, and Their Application to Asymmetric Syntheses

We have synthesized (Ra*)-(R*)2-2,2'-bis(1-hydroxy-1H-perfluoroalkyl)biphenyls, axially dissymmetric ligands with two chiral centers. Their titanium complex induces high enantioselectivity in the reaction of an aldehyde with dialkylzinc. Other reactions of these ligands as a chiral ligand or a chiral auxiliary will be presented. The ligand with long perfluoroalkyl sidechains can be extracted selectively with a fluorous solvent such as perfluorohexane. This enables it to be recovered easily by a fluorous phase separation technique and to be used repeatedly.