1 H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Part III:* Vinclozolin

The 60 MHz ¹H NMR spectra of racemic vinclozolin, 1, have been studied at 28° in CDCI₃ solution with the achiral reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)-d-camphorato] europium(III), 3, and tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium(III), 4. Reagent 3 produced only small lanthanide-induced shifts and no observable enantiomeric shift differences, ΔΔδ, with 3:1 molar ratios as high as 1.40. In contrast, chiral reagent 4 produced substantial ΔΔδ for the proton, H_β, at C-2 of the ethenyl group syn to the oxazolidinedione ring and smaller ΔΔδ for the anti proton, H_β, at the above carbon and for the CH₃. With a 4:1 molar ratio of 0.581, ΔΔδ of 7.0 Hz was seen for H_β. A 4:1 ratio of about 0.41 should be optimum for optical purity determinations; as little as 5% of the minor enantiomer should be detectable.