MOLECULAR STRUCTURE OF HETEROCYCLES: ¹⁷O NMR CHEMICAL SHIFTS: TORSION ANGLE RELATIONSHIPS IN 3-ALKYL SUBSTITUTED 4,5-DIHYDROISOXAZOLES AND ISOXAZOLES^†

Abstract

A quantitative relationship between the ¹⁷O substituent chemical shifts (SCS) of γ-alkyl substituents and the torsion angles calculated by the AM1 method is reported. A series of 3-alkyl substituted 5-trichloromethyl-5-hydroxy-4,5-dihydroisoxazoles and 5-trichloromethyl isoxazoles [where 3-alkyl substituents are Me, Et, n-Pr, iso-Bu, BrCH₂, iso-Pr, Br₂CH and tert-Bu] as model compounds were used.

†For Parts 1–6, see References 14-15a, 15b-16, [19a], [19b].

Keywords:

• NMR
• ¹⁷O NMR
• Isoxazoles
• MO calculations

ACKNOWLEDGMENTS

The authors thank the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq Proc. 46.0804/00-6 and CNPq/PADCT III, Proc. 62.0228/97-0), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS) for financial support. The fellowships from CNPq, CAPES and FAPERGS are also acknowledged.

Notes

†For Parts 1–6, see References 14-15a, 15b-16, [19a], [19b].