Sulfoxides bonding

From single-crystal X-ray structural analysis the ground-state conformation of (.S )-2-(4-meth-ylphenylsulfinyl)-2-cyclopentenone was shown to have the sulfoxide bond orientated anti to the carbonyl bond, as expected for minimization of electrostatic interactions13. 

G(CH3S02 ) is the yield of CH3S02 radicals, AOH- and AH+ are the decrease and increase of the conductivity in basic and acidic solutions respectively, l is the specific conductivity and l(Haq+) and i(OH ) are known to be 315 and 178 fl-1 cm2, respectively. For dimethyl sulfoxide G(RS02 ) was found to be 5.46 comparing this to G(OH) = 6.0 for N20 -saturated aqueous solution leads to the conclusion that 91% of the OH radicals were added to the sulfoxide bond. There is no proof for the fate of the other 9% it is probable that they abstract hydrogen atoms from the methyl groups. 

The P-addition of alkyl radicals to 4-methyl-2-(arylsulfinyl)-2-cyclopentenone 117 has been shown to occur in a completely stereocontrolled manner. Of a mixture of (4/ )- and (45)-117, only (4R)-117 reacts with t-Bu and i-Pr radicals to give the trans adducts 119a and 119b in 99% yield, while (45)-117 remained entirely unreacted. The stereochemical outcome of the reaction shows that the alkyl radical approaches from the side opposite to the aryl moiety in an antiperiplanar orientation to the carbonyl and sulfoxide bond. The 2,4,6-triisopropylphenyl group on sulfur plays a critical role, as it effectively shields the olefin face at the P-position by one of the isopropyl groups. This was confirmed by the 1 1 diastereomeric mixture obtained in the reaction of 4-methyl-2-(p-tolylsulfmyl)-2-cyclopentanone with the tert-butyl radical. 

Jenks et al. studied the effects of conjugation and aromaticity on the sulfoxide bond by means of ab initio computation <1996JOC1275>. They calculated S-O bond dissociation energies (BDEs) and found that, in a formally aromatic system such as thiophene sulfoxide, the SO BDE is decreased by as much as 25kcalmoP relative to the BDE of DMSO. Although the BDE of the formally antiaromatic thiirene sulfoxide increased by about 15 kcal moP the authors concluded, on the basis of calculated geometries and isodesmic reactions with pure hydrocarbons, that cyclic unsaturated sulfoxides are neither significantly aromatic nor antiaromatic. 

NMR spectroscopy has been the most useful tool in cephalosporin C chemistry. In cephalosporins the carbons are unsaturated or highly substituted with heteroatoms, and the protons are usually widely separated in chemical shift and have simple coupling patterns. Recently, solvent induced chemical shifts, nuclear Overhauser effects, and the anisotropy of the sulfoxide bond have been utilized in chemical studies of cephalosporin C derivatives. Analytical information may be derived from NMR spectra of cephalothin by observing the contribution of the 0-lactam protons, thiophene protons, methylene groups, and methyl protons (from acetate). 

The cleavage of a carbon-sulfoxide bond by butyllithium33 is used in the following reaction sequence34 in which the intermediate lithium compound is protonated to 9 by the newly formed sulfoxide35. 

We begin with a brief discussion of the sulfoxide chromophore itself. It will be seen that, just as the sulfoxide bond does not lend itself to simple description, the chromophore is fairly well understood phenomenologically but not yet well described in the shorthand photochemists have developed for other functional groups. Sections III through VII constitute the bulk of the paper and develop the chemistry of conjugated sulfoxides by reaction type. The photochemistry of aliphatic sulfoxides is discussed in Section VIII, with emphasis on gas phase reactions. 

P2i2i2j Z = 4 D = 1.46 R = 0.105 for 961 intensities (film measurements). Compound obtained by glycol cleavage of methyl 6-O-trityl-a-D-glucopyranoside, followed by reduction, sulfonylation, and ring-closure by sulfide anion. The 1,4-oxathiane ring has a distorted chair conformation, with the sulfoxide bond equatorial and the bond to the methoxyl group axial. 

The oxidation of PASs with ozone leads to the formation of poly(aryl-ene sulfoxide)s with a high selectivity. This reaction takes place although ozone is an extremely strong oxidant. Thus, an appropriate amount of ozone enables either to partially or completely convert the sulfur bond into the sulfoxide bond. ° The oxidation is carried out in an ozone/inert gas stream in which the ozone is present in a concentration of 2-6% by volume. The selection of the suspension medium has a decisive influence. In methylene chloride suspension, complete oxidation to the sulfoxide is achieved in a short time. 

Activated sulfoxides are well-known for use as electrophiles (Swem method). The polymerization of the sulfoxide compound is initiated via the sulfonium cation as an active species by the protonation on the oxygen of the sulfoxide bond. The active species electrophilically substitutes on the benzene ring to eliminate water. 

The demethylation of poly[methyl[4-(phcnylthio)phcnyl] sulfonium cation] was carried out in refluxing pyridine. The precursor polymer is completely soluble in the mixture at room temperature, however on reaction a initially white insoluble powder precipitated which was identified as -Methylpyridinium trifluoromethane sulfonate salt. This was isolated quantitatively from the reaction mixture. The resulting polymer has the empirical formula of C6H4S and shows the same IR spectrum and CP/MAS 13C NMR spectra of commercially available PPS. No absorption bands of methyl, sulfone, and sulfoxide bonds are detected in the IR spectrum. 

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