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DOI: 10.1039/A900491B (Paper) Reference Section for: Chem. Commun., 1999, 527-528

Unprecedented use of 29Si NMR spectroscopy for a convenient determination of enantiomeric excesses of chiral α-C-silylated amines and alcohols†

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Frederic Fortis, Jean-Paul Picard, Bernard Barbe and Michel Pétraud

Abstract

The use of routine refocused-decoupled INEPT 29Si NMR spectroscopy, in the presence of the chiral lanthanide shift reagent Eu(tfc)3, allows convenient enantiomeric excess determination of chiral α-C-silylated amines and alcohols for the first time.

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  12. A representative procedure is as follows: 20 mg of the substrate was placed in a 5 mm NMR tube, and 4 cm3 of dry CDCl3 and Eu(tfc)3 were added. The tube was sealed under nitrogen with cling-film and shaken briskly by hand to ensure complete dissolution. After 30 min, the 29Si NMR spectrum (39.76 MHZ) was collected (256 scans) at 300 K on a Bruker Avance DPX 200 MHZ spectrometer over a spectral width of 7961 HZ with a repetition delay of 1 s between scans to allow for complete relaxation. INEPT delay time parameters choosen were τ= 0.0357 s and Δ= 0.02 s. Slight line Gaussian multiplication (–1 HZ) was applied to aid resolution. The FIDs were Fourier transformed and phased automatically, the same phase corrections being applied for each sample. Integration gave the relative proportions of the diastereoisomeric complexes as listed in Table 1.
  13. See Table 1, Experiment 1 in ref 6.
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