New Synthetic Routes toward Enantiopure Nitrogen Donor Ligands

New polypyridylic chiral ligands, having either C3 or lower symmetry, have been prepared via a de novo
construction of the pyridine nucleus by means of Kröhnke methodology in the key step. The chiral moieties
of these ligands originate from the monoterpen chiral pool, namely (−)-α-pinene ((−)-14, (−)-15) and
(−)-myrtenal ((−)-9, (−)-10). Extension of the above-mentioned asymmetric synthesis procedure to the
preparation of enantiopure derivatives of some commonly used polypyridylic ligands has been achieved
through a new aldehyde building block ((−)-16). As an example, the synthesis of a chiral derivative of
N,N-bis(2-pyridylmethyl)ethylamine (bpea) ligand, (−)-19, has been performed to illustrate the viability
of the method. The coordinative ability of the ligands has been tested through the synthesis and
characterization of complexes [Mn((−)-19)Br2], (−)-20, and [RuCl((−)-10)(bpy)](BF4), (−)-21. Some
preliminary results related to the enantioselective catalytic epoxidation of styrene with the ruthenium
complex are also presented.