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Cherton, JC ; Beaufour, M ; Menguy, L ; Merelli, B

Determination of the enantiomeric composition of chiral Delta-2-oxazolines-1,3 by H-1 and F-19 NMR spectroscopy using chiral lanthanide-shift reagents

Spectroscopy Letters 35 (3) 415-437

par Administrateur - publié le

Abstract :

The 300 MHz H-1 NMR spectra of 2-ethyl Delta(2) -oxazoline 1m have been studied in CCl4, CD3CN and C6D6 solutions, in the presence of the achiral lanthanide shift reagent (LSR), tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)-europium III, 4 known as Eu(fod)(3), (see Sch. 1). All the protons of 1 were deshielded at various extent, and the sequence observed for their Deltadelta suggested a major complexation at the basic N(3) center of the heterocycle. Then the chiral monosubstituted oxazoline 1e and the disubstituted oxazolines 1Aa-d and 1Ba, were studied in the presence of chiral LSR, tris-[D, D dicampholylmethanato] europium III Eu(dcM)(3) 5 and tris-[3-(heptafluoropropylhydroxy-methylene)-d-camphorato] praseodym III Pr(hfC)(3) 6. H-1 NMR, and eventually F-19[H-1] NMR spectra were mostly recorded in C6D6 solution.