1H, 1 3C,and 1 5N Chemical shifts and 1H-1 5N and 1 3C-1 5N heteronuclear spin-spin coupling constants in the NMR spectra of 5-substituted furfural oximes

The ¹H, ¹³C, and ¹⁵N NMR spectra of ¹⁵N-enriched 5-substituted furfural oximes were investigated. It was shown that the chemical shifts of the ring atoms and the oxime group correlate satisfactorily with the F and R substituent constants, whereas their sensitivity to the effect of the substituents is lower than in monosubstituted furan derivatives. The constants of spin-spin coupling between the ring protons and the oxime group were determined. An analysis of the ¹H-¹H spin-spin coupling constants (SSCC) on the basis of their stereospecificity indicates that the E isomers have primarily an s-trans conformation in polar dimethyl sulfoxide, whereas the Z isomers, on the other hand, have an s-cis conformation. The signs of the direct and geminal ¹³C-¹⁵N SSCC were determined for 5-trimethylsilylfurfural oxime.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1177, September, 1985.The authors thank N. O. Saldabol, L. M. Ignatovich, and N. P. Erchak for providing us with the investigated compounds.