17O n.m.r. studies of enol and phenol compounds with intramolecular hydrogen bonds

Abstract

The natural abundance 40.67 MHz 1 7 0 n.m.r. spectra of enol and phenol (naphthol) compounds with intramolecular hydrogen bonds are reported and the chemical shifts of the chelated hydroxy groups are assigned.

NMR of enaminones. part 6—17O and13C NMR study of tautomerization in Schiff bases

“…13,14,17 The 17O signal for the CxO oxygen of a,b-unsaturated ketones.13,18 appears at ca. 530 ppm and for that of enaminones at ca.…”

Substituent and temperature controlled tautomerism: multinuclear magnetic resonance, X-ray, and theoretical studies on 2-phenacylquinolines

“…29 Although in the course of this work the temperature and solvent in 15 N NMR experiments were always the same, the relative contributions of the ketimine and enaminone forms were not constant owing to their strong dependence on substituents. 13 C NMR spectra (see Table 2) also allow one to distinguish between different tautomers. In general, δ 13 C values increase (downfield effect) when R becomes more electron accepting for C11 and C12 in the ketimine and for C2 in the enaminone forms.…”

“…[9][10][11] Various NMR techniques have been used to study the conformation and configuration of enaminones. 7-9,11- 13 Similarly, multinuclear magnetic resonance spectroscopic techniques have provided an excellent tool to investigate tautomeric equilibria quantitatively. 4,14, 15 It has been reported that protonationcaused chemical shifts of the ring nitrogen atom in aza aromatic compounds are very large.…”

The crystal and molecular structures of 2-hydroxy-1-naphthalenecarboxaldehyde and 3-hydroxy-2-naphthalenecarboxaldehyde

“…There are continuous studies which have appeared on the title compounds, due to the diverse properties of these compounds, i.e., spectroscopic studies (Vargas et al, 1985;Lapachev et al, 1985;Razniewska-Lazecka et al, 1986), studies concerning their biological activity such as bacterial, fungicidal or spermicidal (Khorana et al, 1967;Sharma et al, 1980;Wang et al, 1990), or their use as starting materials for the preparation of Schiff base compounds which are frequently used as ligands for complexing transition metals (MacDonald et al, 1982;Fern~.ndez-G. et al, 1987;Elerman et al, 1991). However, there have been no reports, to our knowledge, on the single crystal X-ray diffraction study of compounds I or II.…”