title: Self-assembly of achiral and chiral macrocyclic ligands: synthesis, protonation constants, conformation and asymmetric catalysis.
abstract: New 30-membered achiral and chiral polyaza macrocyclic ligands, L1 and L2 were synthesized directly from [3 + 3] condensation of phthalic dicarboxaldehyde with cis- and (1R,2R)-diaminocyclohexane, respectively. The trimeric macrocyclic structures were confirmed by electrospray ionization mass spectrometry (ESI-MS), 1H NMR, 13C NMR spectroscopy and elemental analysis. Potentiometry was used to determine the protonation constants of the ligands. UV-vis spectrophotometric titration was employed to investigate the coordination and conformational properties of the chiral ligand (L2). Direct enantioselective aldol reaction has been successfully performed using 4-nitrobenzaldehyde and acetone in the presence of the chiral macrocycle and its zinc(II) complexes as catalysts.
authors.affiliation: Department of Chemistry, Texas A & M University, College Station, Texas 77843-3255, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Gao
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Martell