Abstract
The 60 MHz 1H NMR spectra of racemic ketazolam, 1, have been studied at 28° in CDCl3 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 reagent tris[3-(heptafluoropropylhydroxymethyl- ene)-d-camphoratoleuropium(III), 3. Dramatic differences in lanthanide-induced shifts,Δδ, were observed for the diastereotopic CH2 protons with either added 2 or 1. Differences in these Δδ valuest as well as differences in lanthanide-induced line broadening and in enantiomeric shift differences (observed with 3) are interpreted in terms of a relatively rigid preferred conformation of 1. Assignments for the CH2 protons are made. Direct optical purity determinations for samples of l should be possible by use of 3, based on resonances for either of the CH2 protons or the allylic CH3.