Motohiro Nishio

X-Ray study of (αS,SS/αR,SR)-1-(p-bromophenyl)ethyl t-butyl sulphoxide and conformational analysis of diastereoisomeric pairs of 1-phenylethyl t-butyl sulphoxides

The title compound, C12H17BrOS, is monoclinic, space group P21/n, a= 12.87(1), b= 6.005(6), c= 17.32(2)A, β= 90.37°Z= 4, Dm= 1.434 g cm–3. The structure was solved by the heavy-atom method and refined to an R value of 0.09. It has been shown that the bulkiest group (But) orients itself anti to the methyl group and gauche to the phenyl group. Solution phenomena (n.m.r. and o.r.d.–c.d. data) of some diastereoisomeric pairs of 1-phenylethyl t-butyl sulphoxides are best interpreted by assuming that the predominant conformations of these molecules resemble those found in X-ray crystallographic studies.

Electronic substituent effect on intramolecular CH/π interaction as evidenced by NOE experiments

In order to demonstrate the hydrogen-bond-like character of the CH/π interaction, electronic substituent effects on the equilibria between the stretched and the folded conformers of series of compounds capable of forming CH/π interactions were examined by measurements of NOE enhancements of 1H NMR signals. Nuclear Overhauser enhancement is shown to be useful to determine the abundance of the CH/π proximate folded conformer. The Hammett plots of all series of the compounds capable of having CH/π interaction gave negative ρ values. Together with other substituent effects (effects of electronegative substituents, on the CH donor, of ring size, and of α-alkyl substituent), the involvement of delocalization interaction and the hydrogen-bond-like character of the CH/π interaction were established.

Effect of CH/π interaction on the chiroptical properties of olefins and dienes

Abstract Rotatory strengths of exo-methylenesteroids, α-phellandrene and related compounds were calculated on the basis of Rosenfeld theory by using AM1 molecular orbitals. Calculation showed that a considerable change in intensity of CD band is expected to occur for the conformers where CH/π interaction is possible. Chiroptical properties of asymmetric olefins and dienes were interpreted from the viewpoint of CH/π interaction.

Theoretical study of CH-π interaction. Significant enhancement of CD spectra due to the participation of CH-π interaction.

Abstract Rotatory strengths of α-phellandrene and related compounds were calculated on the basis of Rosenfeld theory by using AM1 molecular orbitals. Calculated geometries and rotatory strengths indicated that significant enhancement of CD spectrum would be expected to occur for the conformers where CH-π interaction was possible.

Gas–liquid partition chromatographic evidence that alkyl–phenyl interactions are specific for the shape of the alkyl group

Gas chromatographic studies have shown that the weak interaction between an alkane sample and the phenyl group in a stationary liquid varies in strength with the geometrical shape of the alkyl group and is more attractive for a cyclic alkyl group than for the corresponding straight-chain alkyl group.

X-Ray structure determination of 1-(p-bromophenyl)ethyl t-butyl sulphoxide. Configuration and conformation

X-Ray structural analysis of 1-(p-bromophenyl)-ethyl t-butyl sulphoxide supports chemical correlation results; the t-butyl group orients itself in the gauche-position to the phenyl group.

Absolute configuration of 1-phenylethyl p-tolyl sulphoxides and the stereochemistry in the oxidation of 1-phenylethyl p-tolyl sulphide

The absolute configurations of diastereoisomeric 1-phenylethyl p-tolyl sulphoxides have been established by o.r.d. and c.d. observations and these are in agreement with those obtained from chemical correlations. The stereochemistry of the oxidation of 1-phenylethyl p-tolyl sulphide to the sulphoxides is discussed in the light of the observed isomer distributions.