Enantiomeric Differentiation of Oxygenated Bicyclo[2.2.1]heptane Derivatives by ¹³C NMR Spectroscopy Using Yb(hfc)₃

ABSTRACT

The ¹³C NMR behavior of 10 oxygenated compounds (ketones, alcohols, acetates) bearing the bicyclo[2.2.1]heptane skeleton was examined in the presence of a chiral lanthanide shift reagent (Yb(hfc)₃). For each compound, we measured the lanthanide-induced shift (LIS) on the signals of the carbons and the splitting of signals, enabling the enantiomeric differentiation. The enantiomeric splitting was observed for the majority of signals in the spectrum of each compound.

KEYWORDS:

• ¹³C NMR
• bicyclo[2.2.1]heptane derivatives
• borneol
• chiral lanthanide shift reagent
• enantiomeric differentiation
• Ytterbium

ACKNOWLEDGMENTS

The authors are grateful to the Collectivité Territoriale de Corse (CTC) for financial support.

Notes

^§Signal of carbon C2 split quickly, and it was impossible to draw the slope.

∗δ (ppm) of acyl group: 4 C[dbnd]O (170.81) CH₃ (21.41); 5 C[dbnd]O (171.27) CH₃ (21.20).

^§The signal of carbon C2 split quickly, and it was impossible to drawn the slope needed for normalized data.

^#Signals of carbons C3 and C7 split very lightly and only when the above ratio reached 0.25.

∗δ (ppm) of acyl group: 9 C[dbnd]O (170.67) CH₃ (21.32); 10 C[dbnd]O (171.41) CH₃ (21.29).