Jump to main content
Jump to site search

Issue 4, 2015
Previous Article Next Article

Amino acid derived CuII compounds as catalysts for asymmetric oxidative coupling of 2-naphthol

Author affiliations

Abstract

We report the synthesis and characterization of several novel aminopyridine – L-amino acid derived CuII-complexes. The ligands are prepared by a one-pot reductive alkylation of the L-amino acid scaffold and the respective aminopyridine CuII-complexes were obtained by reaction with CuCl2 or Cu(acetato)2. All compounds were characterized by spectroscopic techniques, as well as ESI-MS. Two of the CuII-complexes were characterized by single-crystal X-ray diffraction, one of them, [CuII(L)(CH3COO)] (HL = (S)-3-phenyl-2-(pyridin-2-ylmethylamino)propanoic acid), being the first ever reported aminopyridine-class CuII complex bearing a tridentate N,N,O donor set and a monodentate acetato ligand. The complexes are tested as catalysts in the oxidative coupling of 2-naphthol in organic solvent–water mixtures using dioxygen as the terminal oxidant. The effect of variables such as ligand denticity and substituents, as well as solvent, temperature and oxidant intake, on the overall performance is studied. In general, moderate to low conversions of 2-naphthol to 1,1′-bi-2-naphthol (BINOL) are obtained. The catalysts also showed moderate to low enantioselectivity. Some aspects of the reaction mechanism were elucidated by spectroscopy, electrochemical and theoretical studies. It was found that basic additives are important for activity, but these also increase the formation of secondary oxidation products. The addition of peroxide scavengers such as KI resulted in an increase of conversion, the yield of BINOL and enantioselectivity.

Graphical abstract: Amino acid derived CuII compounds as catalysts for asymmetric oxidative coupling of 2-naphthol

Back to tab navigation

Supplementary files

Publication details

The article was received on 08 Sep 2014, accepted on 14 Oct 2014 and first published on 20 Oct 2014


Article type: Paper
DOI: 10.1039/C4DT02731K
Citation: Dalton Trans., 2015,44, 1612-1626
  •   Request permissions

    Amino acid derived CuII compounds as catalysts for asymmetric oxidative coupling of 2-naphthol

    P. Adão, S. Barroso, M. F. N. N. Carvalho, C. M. Teixeira, M. L. Kuznetsov and J. Costa Pessoa, Dalton Trans., 2015, 44, 1612
    DOI: 10.1039/C4DT02731K

Search articles by author

Spotlight

Advertisements