60805-87-0Relevant academic research and scientific papers
A generalized exo-anomeric effect. Substituent and solvent effects on the conformational equilibria of 2-(Arylseleno)cyclohexanones
McLeod, Ronald G.,Johnston, Blair D.,Pinto, B. Mario
, p. 307 - 316 (2007/10/03)
The effects of substitution and solvent on the conformational equilibria of 2-[(4-R-substituted-phenyl)seleno]cyclohexanones are described. The conformational equilibria were determined by comparison of the linewidths of the H-2 resonances in the 1H NMR spectra of the conformationally averaged systems with those of the anancomeric (highly biased) 4-isopropyl-2-substituted cyclohexanones. The substituent (R = NMe2, OMe, Me, H, F, Cl, CF3, NO2) and solvent ((CD3)2CO, CD3CN, CD2Cl2, CDCl3) effects are discussed in terms of electrostatic effects and the possible stabilizing orbital interactions. The values of Keq (axial-equatorial) increase as the substituent becomes more electron withdrawing, in agreement with the dominance of nSe→π*C=O or σC-Se→π*C=O orbital interactions in the axial conformers. The increase in the proportion of the equatorial isomers in more polar solvents for a given substituent suggests a damping of the dipolar interactions in the equatorial isomers. However, the proportion of the equatorial isomers in a given solvent increases as the substituent becomes more electron withdrawing, indicating that electrostatic interactions do not dominate in controlling the conformational equilibria. Analysis of the equilibrium data by means of a dual substituent parameter approach indicates the best correlation with σI and σ+R substituent constants in CD2Cl2, and with σI and σOR substituent constants in CD3CN, with similar sensitivities to the resonance and polar effects. The correlations are interpreted in terms of accommodation of effective positive charge on the selenium atom in the axial isomers in CD2Cl2, and a lesser sensitivity to the buildup of positive charge in the more polar solvent CD3CN. Comparison of the IR vCO-stretching frequencies for the axial and equatorial ArSe-substituted anancomeric systems (R = NO2, NMe2) indicates a higher stretching frequency for the NO2-substituted isomers. In the case of the NMe2-substituted compounds, vCO appears at a higher frequency in the equatorial isomer, whereas in the case of the NO2-substituted compounds, vCO is less sensitive to the axial or equatorial orientation of the substituent. The results are consistent with the operation of nSe→π*C=O or σC-Se→π*C=O orbital interactions in the axial isomers. The JC2-H2 values in the axially-substituted anancomeric isomers are of greater magnitude than those in the equatorially-substituted isomers, which is also consistent with the operation of the orbital interactions described above. There is, however, no marked substituent effect on the JC2-H2 values within the series of axial or equatorial isomers. We argue that this does not support the dominance of σC-Se→π*C=O orbital interactions. Examination of crystal structures reported in the literature for related compounds indicates a particular gauche orientation about the C2-Se bond, which lends further support to the operation of an nSe→π*C=O orbital interaction. We suggest that the latter interaction is a manifestation of a generalized exo-anomeric effect.
Oxidation of α-sulfonyl selenides: Formation of selenolesters
Yi, Jae Sang,Kim, Kyongtae
, p. 71 - 76 (2007/10/03)
Treatment of 7-phenylseleno-7,12-dihydrobenzo[5,6][1,3]thiazepino[3,2-a]benzimidazole 6,6-dioxide 7a in CH2Cl2 with m-chloroperbenzoic acid (MCPBA) and 28% H2O2 at room temperature gave Se-phenyl 2-[(benzimidazol-l-yl)methyl]selenobenzoate 8a. Similarly, the oxidation of sulfone 7a in THF with aqueous Oxone7 at room temperature gave the same selenolester 8a. The formation of selenolesters 8 can be explained by assuming either the involvement of oxaseleniranium cation 13, having a sulfinate group at C-2 of the benzimidazole moiety, as an intermediate which is believed to be formed by an intramolecular nucleophilic attack of the polarized oxygen of the Se=O bond of selenoxide 6 to the α-carbon next to the sulfonyl group, or Pummerer-type reactions.
Reactions of Enolates with Vinyl Selenoxides and Vinyl Selenones. One-Step Synthesis of Cyclopropylcarbonyl Compounds
Ando, Ryoichi,Sugawara, Tomoo,Shimizu, Makoto,Kuwajima, Isao
, p. 2897 - 2904 (2007/10/02)
In the reactions with enolate anions, organoselenium moieties of aryl vinyl selenoxides and selenones have exhibited two important roles, e.g., activation of C=C bonds for conjugate addition reaction and behaviors as excellent leaving groups.Owing to such characteristic fetaures, ketone enolates react with p-chlorophenyl vinyl selenoxide to afford the corresponding cyclopropyl ketones through an initial conjugate addition followed by substitution processes.On the other hand, use of vinyl selenones usually gives much better results with anionic species of active methylene compounds.Vinyl selenones bearing hydroxyl, ketone, and ester groups can also be employed equally well for this type of transformation.
