Synthesis of new C2-symmetric bis(β-hydroxy amide) ligands and their applications in the enantioselective addition of alkynylzinc to aldehydes

A series of chiral C2-symmetric bis(β-hydroxy amide) ligands was synthesized via the reaction of isophthaloyl dichloride and amino alcohols derived from l-amino acid. The titanium(IV) complex of C2-symmetric chiral ligand 3b was effective for the asymmetric alkynylation of aldehydes and the propargyl alcohols were obtained in high yields (up to 94%) and high enantiomeric excesses (up to 98%) under optimized conditions. The results obtained using ligand 3h support that the two β-hydroxy amide moieties in these ligands behave as two independent ligands in the catalytic system.