Giovanni Cerioni

C-13 and O-17 NMR studies on N-sulfinylanilines

Abstract N-sulfinylanilines have been studied by C-13 and O-17 NMR in chloroform and pyridine; they interact with pyridine, yielding a complex which is stable in solution. The study by O-17 NMR spectroscopy shows that for the NSO group the SO bond is a true π bond.

Characterization of 2,5-diaryl-1,3,4-oxadiazolines by multinuclear magnetic resonance and density functional theory calculations. Investigation on a case of very remote Hammett correlation

Two series of 2,5‐diaryl‐1,3,4‐oxadiazolines have been studied by multinuclear magnetic resonance and density functional theory calculations. A full NMR spectroscopic characterization has been performed and excellent remote Hammett correlations (σp or

Hydrogen bonding in calix[n]arenes. A preliminary 17O NMR study

\sigma_{\rm {p}}^{+}

Dynamic NMR of low-sensitivity fast-relaxing nuclei: 17O NMR and DFT study of acetoxysilanes

) have been found for para substitution in the two aryl rings through at least 11 bonds, notwithstanding the presence in the path of atoms that should act as insulators and a lack of correlation for some of the intermediate atoms. The computational investigation on the electronic delocalization, performed with the ACID (anisotropy of the induced current density) method, reveals indeed that electrons are delocalized in almost the entire molecule despite the presence of the insulators. Copyright

17O NMR STUDIES ON DIALKOXY DISULFIDES

Abstract 17O NMR spectra at natural isotopic abundance of two calix[n]arenes, (n = 4,6) and model phenols have been obtained in three different solvents. The difference in the hydrogen bond strength between calix[4]arene and calix[6]arene is manifested in the 17O NMR spectra.

17O NMR studies on ?-diamides

17O NMR is not routinely used for structure characterization, and kinetic studies of fluxional organic compounds are seldom undertaken because poor sensitivity and fast quadrupole relaxation are frequently regarded as intractable issues. This work shows how, nowadays, quantitative 17O dynamic NMR studies on small organic molecules are feasible without enrichment being needed. It reports on acetoxysilanes, a class of fluxional compounds whose structure and dynamics were to be clarified. Natural abundance 17O NMR spectra were recorded over a wide range of temperatures using standard instrumentation. The analysis relies on simple linewidth measurements and directly provides the activation parameters. The activation enthalpy is found to decrease with increasing number of acetoxy groups bound to silicon. Density functional theory calculations properly predict this trend and show that a single oxygen atom of the acetoxy group is bound to silicon, excluding chelation as binding mode, and that the dynamic process involves the shift of the silicon atom between the two oxygen atoms of the acetoxy group. Copyright

HETEROCYCLIC COMPOUNDS STUDIES, SYNTHESIS OF 1,5-BENZOXATHIEPINES

17O NMR spectra, at natural isotopic abundance, of dialkoxy disulfides are presented and β‐ and γ‐SCS effects shortly discussed.

On the Fluxional Behavior of Dess−Martin Periodinane: A DFT and 17O NMR Study

17O NMR spectra of several α-diamides were obtained at natural isotopic abundance in acetonitrile solution in order to study the conformations of these compounds in solution. The 17O NMR shifts vary with the intercarbonyl dihedral angle α in a sense opposite to that observed for α-diketones.

NMR of terminal oxygen. Part 12. SO2 and isoelectronic compounds with a true π-bond: 17O NMR spectra of sulfinylamines R–NSO and sulfines RR′CSO. The conformation of ortho-substituted diaryl sulfines

Abstract 1,5-Benzoxathiepinic derivatives have been obtained in good yields by the reaction of epichlorohydrines with 2-hydroxybenzenethiols in an aqueous alkalinic hydroxides medium. Their structures have been determined by 13C NMR spectroscopy.

Mechanism of decarbalkoxylation of arylmethylene-propanedioic acid dimethyl esters

The structure and dynamics of the Dess-Martin periodinane, a I(V) iodobenzene compound widely used in organic synthesis as a mild oxidant, were studied by a combined (17)O NMR and DFT calculations approach. The results show that a degenerate [1,3] sigmatropic shift of iodine between the two oxygen atoms of each of the three acetoxy groups occurs in solution. The energy barrier of this process depends on the position of the acetoxy group with respect to the iodoxolone ring and is much lower than the energy barrier observed for similar I(III) compounds.