The combined use of 1H NMR spectroscopy with theoretical calculations of chemical shifts (GIAO) and coupling constants (B3LYP/6-311 ++G**) of a 5-hydroxy-5-trifluoromethyl-Delta2-isoxazoline has enabled solving the problem of the assignments of the diastereotopic protons in this compound. This result has been extended to 5-hydroxy-5-trifluoromethyl-Delta2-pyrazolines and the corresponding 5-trichloromethyl derivatives.
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