NMR Studies of Agricultural Compounds. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Multifunctional Compound, Imazapyr Methyl Ester.

Abstract

Abstract The 60 MHz 1H NMR spectra of the methyl ester derivative, 1, of the imidazolinone herbicide, imazapyr, have been studied in CDC13 at 28±1° (as the racemic free base) with the added achiral lanthanide shift reagent (LSR), tris(6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium (III), 2, for spectral simplification, and with the chiral LSR, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III), 3, to induce enantiomeric shift differences (ΔΔδ). An additional series of runs employed the chiral LSR, tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorato]europium(III), 4. Substantial lanthanide-induced shifts (LIS) were observed with each added LSR. Added 3. appeared to elicit large ΔΔδ magnitudes for H-6 on the pyridine ring (alpha to nitrogen), whereas 4. caused smaller ΔΔδ values for the quaternary and isopropyl methyls on the imidazolinone ring.