Yb(fod)3 in the spectroscopic determination of the configuration of chiral diols: A survey of the lanthanide diketonate method

Authors

  • Lorenzo Di Bari,

    1. Centro di Studio del CNR per le Macromolecole Stereoordinate ed Otticamente Attive, Dipartimento di Chimica e Chimica Industriale, Pisa, Italy
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  • Moreno Lelli,

    1. Centro di Studio del CNR per le Macromolecole Stereoordinate ed Otticamente Attive, Dipartimento di Chimica e Chimica Industriale, Pisa, Italy
    2. Scuola Normale Superiore, Pisa, Italy
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  • Guido Pintacuda,

    1. Centro di Studio del CNR per le Macromolecole Stereoordinate ed Otticamente Attive, Dipartimento di Chimica e Chimica Industriale, Pisa, Italy
    2. Scuola Normale Superiore, Pisa, Italy
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  • Piero Salvadori

    Corresponding author
    1. Centro di Studio del CNR per le Macromolecole Stereoordinate ed Otticamente Attive, Dipartimento di Chimica e Chimica Industriale, Pisa, Italy
    • Centro di Studio del CNR per le Macromolecole Stereoordinate ed Otticamente Attive, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, I-56126 Pisa, Italy
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  • Dedicated to professor Koji Nakanishi on the occasion of his 75th birthday

    Abbreviations: dpm, dipivalomethanate; acac,acethylacethonate; fod, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate.

Abstract

A modification of the diketonate method for the determination of the absolute configuration of chiral vicinal diols, first proposed by Nakanishi, is taken under object and tested with a set of aliphatic and aromatic substrates; Yb(fod)3 (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) is employed as the chromophoric species. The replacement of dpm (dpm = dipivalomethanate) with fod ensures the formation of strong and stable signals in the UV region, whose signs are related to the configuration of the chelating molecule. The choice of ytterbium as the central cation introduces two major advantages: the electronic f–f transition of the rare-earth supplies a second spectral window in the near-IR, which is sensitive to the chemical environment around the atom. This allowed us to ascertain the number of different species present in solution and the observation of an induced CD also for strongly UV-absorbing substrates. The pseudocontact shifts induced in the 1H-NMR spectrum by the unpaired electron of the lanthanide ion provide valuable structural information on the adducts. Chirality 14:265–273, 2002. © 2002 Wiley-Liss, Inc.

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