Intramolecular Hydrogen Bonding in the Nitrobenzopyridines

Abstract

The available data on the spectroscopy of the nitrobenzopyridines are insufficient, out-dated, and modern theory is missing. A careful study of the 'H-NMR spectra of these compounds revealed the existence of C-H-0-N=0 hydrogen bonds, the hydrogen being at peri position to the nitro group. The existence of these bonds explains the down-field shifts observed in the signals of the involved protons. Spectral data from the naphthalene series and from 1 O-NMR measurements, both involving the nitro group/per/'-hydrogen relation, confirmed our proposal.

Intramolecular Hydrogen Bonding in 2,3-Bis-(3,4-dimethoxybenzoyl)Propionitrile

“…Following our study on intramolecular hydrogen bonding, deduced from 1 H Nuclear Magnetic Resonance Spectroscopy [1][2][3], we now present evidence for the existence of this type of atomic interactions in 2,3-bis-(3,4-dimethoxybenzoyl)propionitrile, 5, in solution in CDCl 3 . This compound was obtained as is described in the next section.…”

Synthesis, stereoelectronic characterization and antiparasitic activity of new 1-benzenesulfonyl-2-methyl-1,2,3,4-tetrahydroquinolines

“…This unexpected unshielding of H8 may have been caused by a dipolar interaction (hydrogen bond) with one oxygen of the BS group. Sanchez-Viesca et al demonstrated evidence of C-HÁ Á ÁO, C-HÁ Á ÁN and C-HÁ Á ÁCl hydrogen bonds in thiazole, 35 benzopyridine 36 and propionitriles 37 derivatives by 1 H NMR experiments with the presence of two intramolecular weak H-bonds of the type C-HÁ Á ÁO in the benzopyridine derivatives leading to a Dd of 1.0-1.2 ppm. 36 Furthermore, based on crystallographic data, Desiraju et al 38,39 observed distances of 2.0-3.0 Å between HÁ Á ÁO, when the H-bond C-HÁ Á ÁO occurred in crystals, for more than 100 analyzed structures.…”