Sulfoxides reagents

The facile and selective oxidation of both primary and secondary hydroxy groups with certain nucleotides led Pfitzner and Moffatt (48) to explore the scope of the carbodiimide-methyl sulfoxide reagent with steroid and alkaloid alcohols. Relatively minor differences were apparent in the rate of oxidation of epimeric pairs of 3- and 17- hydroxy steroids whereas the equatorial lLx-hydroxyl group in several steroids was readily oxidized under conditions where the axial epimer was unreactive [cf. chromic oxide oxidation (51)]. 

However, addition of (+ )-(7 )-l-methyl-4-(mcthylsulfinyl)benzene, to aldehydes and ketones proceeds with low stereoselectivity. An improvement of the 3-syn diaslereoselectivity was found with the zinc reagent obtained by transmetalation of the lithiated sulfoxide with anhydrous zinc chloride38. An improvement of the stereoselectivity was also attained by exchange of the 4-methylphenyl substituent for a 2-methoxyphenyl or 2-pyridinyl substituent. Thus, the introduction of an additional complexing site into the aromatic part of the sulfoxide reagent enhances the stereoselectivity35. 

Derived reagents. Mancuso and Swern2 have reviewed activated dimethyl sulfoxide reagents (100 references). Activation of DMSO with cither trifhioroacelic anhydride (7, 136) or oxalyl chloride (8, 200) provides the most generally useful... 

In this work, we used the dyes provided by the Research Center NllKHlMFOTOPROEKT and commercial chicken DNA (Reanal, Himgary) [7]. DNA concentrations were determined using the extinction coefficient of a base pair of 13200 1 moE cm at a wavelength of 250 nm [8]. An aqueous phosphate buffer solution (pH 7, at a concentration of 20 mmol l ), isopropanol, methanol, isopropanol, hexanol and dimethyl sulfoxide (reagent grade) were used as solvents. 

C-Alkylation Diethyl sulfate. Dimethyl sulfate. Dimethyl sulfoxide reagent (a). Methyl bromide. Methyl chloride. Nitrosonium hexafluorophosphate. Potassium r-butoxide. Sodium amide, Sodium ethoxide. Sodium 2-methyl-2-butoxide. Tetramethylurea. Tri-ethyloxonlum fluuruburate. Trimcthyloxonium fluurubomte. Trimethyloxonium 2,4,6-trlnltrobenzene lulfonale. Triiyliodium. 

Soluble linear polystyrene can also be used to prepare recyclable sulfoxide reagents for Swern oxidations [104]. While the styrene copolymer sulfoxides 68 are not strictly catalysts, they are easily recycled by precipitation with cold methanol. Reoxidation of the sulfide with f-BuOOH reformed the starting polymeric sulfoxide 68. While some decrease in yield was seen from cycle to cycle through four cycles, the products were not contaminated with polymer - an advantage in high throughput chemistry where separations need to be as simple as possible. 

The applications reported for polymer-supported, soluble oxidation catalysts are the use of poly(vinylbenzyl)trimethylammonium chloride for the autooxidation of 2,6-di-tert-butylphenol [8], of copper polyaniline nanocomposites for the Wacker oxidation reaction [9], of cationic polymers containing cobalt(II) phthalocyanate for the autooxidation of 2-mercaptoethanol [10] and oxidation of olefins [11], of polymer-bound phthalocyanines for oxidative decomposition of polychlorophenols [12], and of a norbornene-based polymer with polymer-fixed manganese(IV) complexes for the catalytic oxidation of alkanes [13], Noncatalytic processes can also be found, such as the use of soluble polystyrene-based sulfoxide reagents for Swern oxidation [14], The reactions listed above will be described in more detail in the following paragraphs. 

These results, along with quantum mechanical calculations, supported the conclusion that a six-membered chelated flat-chairlike transition state operated under the kinetic conditions. The diastereoselectivity of reactions between Li-salts of the (/ )-methyl p-tolyl sulfoxide formed by a-deprotonation with -BuLi, could be further enhanced by the addition of external C2-synunetrical bidentate ligand (7 ,7 )-l,2-M,M-bis(trifluoromethanesulfonyla-mino)cyclohexane in the form of the lithium M,M-dianion providing the amine in 80% yield with a diastereoselectivity of 99 1, apparently achieving a match between the chirality of the additive and the chirality of the sulfoxide reagent. 

The lactone moiety 6 found in mevinic acids has been synthesized from L-malic acid using a chiral sulfoxide reagent to control the stereochemistry at C-3. Synthesis of the negamycin lactone 7 has been reported, while a lactone precursor of L-acosamine and L-daunosamine is discussed in Chapter 9. 

Shen T, Huang X, Liang YF, Jiao N (2015) Cu-catalyzed transformation of alkynes and alkenes with azideand dimethyl sulfoxide reagents. Oig Lett 17(24) 6186-6189... 

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