Sulfoxides lateral

Sulfoxides have the potential for chirality—the tetrahedral sulfur atom is surrounded by four different groups (here Ph, Me, D, and the lone pair) and (unlike, say. the tetrahedral nitrogen atom of an amide) has a stable tetrahedral configuration. We will revisit chirality in sulfoxides later in the chapter. 

A graphite electrode modified chemically with L-phenylalanine gave an ee of 9.7% in the reduction of phenylglyoxalic acid into mandelic acid and an ee of 2.5% in the oxidation of methyl / -tolyl sulfide into its sulfoxide Later this oxidation reaction was improved... 

Sugars are very good candidates for the measurement of VCD as the more common ECD is dependent on a chromophore, which is almost always absent in this class of natural compounds. The examination of the VCD spectra of six common sugars revealed a chirality rule for the 1150 cm band in deuterated dimethyl sulfoxide. Later the FT-VCD spectra of the carbohydrates D-fucose, D-arabinose, D-ribose, D-galactose and D-glucose [25] and their isotopomers deuterated at the hydroxyl group were examined in the same solvent. Some useful correlations between structure and spectra are found, but also some deviations. 

In sulfoxides and sulfones an adjacent CH group is also deprotonated by strong bases. If one considers the sulfinyl (—SO—) or sulfonyl (—SOj—) groups to be functional groups, then these carbanions are d -synthons. It will be shown later (p. 48f. and 65f.), that these anions may either serve as nonfunctional, d -, d - or d -synthons. 

Alkenyl sulfoxides (42 and 43) were first prepared in optically active form by Mulvaney and Ottaviani , described in an article overlooked by most workers in the field, and a year later by Stirling and coworkers through the reaction of the appropriate vinyl Grignard reagent with sulfinate ester 19. Both groups studied the addition of nucleophiles to the carbon-carbon double bond . More recently, Posner and coworkers reported a similar synthesis of ( )-l-alkenyl sulfoxides, e.g. 44 and In the synthesis of 45,... 

Oae and Khim measured the rates of hydrolysis of chlorophenyl phenyl sulfoxides and sulfones with hydroxide ion in aqueous DMSO at 158 °C. Both SOPh and S02Ph were found to activate the nucleophilic substitution from ortho- and para-positions, but the effect of SOjPh was considerably larger than that of SOPh. The results were interpreted in terms of 7t(pd) conjugation in the intermediate complexes. In a later paper it was shown that the introduction of a methyl group ortho to SOPh or S02Ph slightly retards the above and related reactions but this was attributed to the inductive effect of Me rather than steric inhibition of 7t(pd) conjugation (Section III.A.l). 

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Oae and Numata26 were the first to postulate formation of a disulfonium dication in reaction of concentrated sulfuric acid with monosulfoxide of a bis-sulfide. Later Furukawa et al.62 found that the crystalline hydrosulfate 36 can be prepared by reaction of the corresponding monosulfoxide 13 (or A-tosyli-mide 14) with concentrated sulfuric acid. Formation of a symmetric dication 38 was confirmed by isolation of 1 1 mixture of deuterated sulfoxides 37 and 39... 

The sulfoxide method has been applied to the concept [319,374] of intramolecular aglycone delivery for the formation of [1-mannosidcs by means of a silylene linker. In the original work, the acceptor and a thioglycoside donor were joined by means of a silylene group before the oxidation to the sulfoxide [141]. However, it was later found that the preformed sulfoxide was tolerated by the chemistry for the introduction of the linker [286,375]. The intramolecular aglycone delivery step was shown to function effectively for the transfer of the donor to the 2-, 3- and 6-position of glucopyr-anosides, as exemplified in Scheme 4.64. 

Later on, Christensen (134,135) showed that the reaction of chiral sulfoxides with A -sulfinyl-p-toluenesulfonamide in benzene as well as... 

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