Sulfides to sulfones

An effective reagent for this is RuCyaq. IO(OH)3/CCl -CH3CN, used for oxidation of the lactone (2R,3R,4R)-2-methyl-2-phenylthio-3-methoxycarbonyl-methyl-4-(2 -tert-butyl-diphenylsilyloxy)ethyl-y-butyrolactone to the sulfonyl analogue (Fig. 5.16) other oxidations are listed in Table 5.2 [107]. 

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The conversion of cyclic sulfides to sulfones is accompbshed by more energetic oxidations. Perhalogenated thiolanes [106] and 1,3-dithietanes [107] are oxidized to sulfones and disulfones, respectively, by a mixture of chromium trioxide and nitric acid (equation 98) The same reagent converts 2,4-dichloro-2,4-bis(tnfluoromethyl)-l,3-dif/u cto cs to disulfone derivatives [107], whereas trifluoromethaneperoxysulfonic acid converts the starting compound to a sul-fone-sulfoxide derivative [2(equation 99). 

Sulfones. This oxidant is useful for selective oxidation of sulfides to sulfones (10,328). Oxidations of acid-sensitive substrates should be buffered with Na2C03. 

Scheme 8 summarizes the introduction of the missing carbon atoms and the diastereoselective epoxidation of the C /C double bond using a Sharpless asymmetric epoxidation (SAE) of the allylic alcohol 64. The primary alcohol 62 was converted into the aldehyde 63 which served as the starting material for a Horner-Wadsworth-Emmons (HWE) reaction to afford an E-configured tri-substituted double bond. The next steps introduced the sulfone moiety via a Mukaiyama redox condensation and a subsequent sulfide to sulfone oxidation. The sequence toward the allylic alcohol 64 was com-... 

Oxidations of sulfides catalysed by Ru porphyrin complexes have been reviewed [4, 97, 98]. In their pioneering work of 1953 Djerassi and Engle showed that stoich. RuOyCCl oxidised several sulfides to sulfones (Table 5.2) [99]. 

Oxidation of sulfides and sulfoxides using Oxone dispersed on silica gel or alumina was reported . A study of surface mediated reactivity of Oxone compared its reactivity with that of ferf-butyl hydroperoxide. Oxidation of sulfides to sulfones in aprotic solvents mediated by Oxone on wet montmorillonite or clay minerals proceeds in high yields. Interestingly, when Oxone on alumina is applied for selective oxidation of sulfides in aprotic solvents, the product distribution is temperature-dependent and sulfoxides or sulfones are obtained in good to excellent yields (equation 56) . ... 

THE FIRST EXAMPLE OF DIRECT OXIDATION OF SULFIDES TO SULFONES BY AN OSMATE-MOLECULAR OXYGEN SYSTEM... 

The oxidation of sulfides to sulfones has been the subject of extensive studies, since sulfones are useful synthons for the construction of various chemically and biologically significant moleculesJ Recently, a new catalytic system has been developed by exchanging potassium osmate onto chloride-saturated layered double hydroxides (Figure 9.1), which we have shown to be an efficient catalyst for the direct oxidation of sulfides to sulfones, using molecular oxygen as the stoichiometric oxidant and with delivery of two oxygen atoms simultaneously to the sulfide, reminiscent of olefin dihydroxylation reactions. 

Sulfunes. A recent preparation of thietane 1,1-dioxide1 emphasizes the advantage of tungstic acid catalysis2 in the hydrogen peroxide oxidation of sulfides to sulfones an induction period is eliminated and the yield improved. 

Oxidation of sulfides to sulfones.[ Sulfides are oxidized chemoselectively to sulfones by KHSOs (3 equivalents) in high yield. Peracids are usually used for this oxidation, but can also oxidize olefinic groups. Oxidation of sulfides to sulfoxides is also possible with 1 equivalent of reagent. 

A recent method for the highly chemoselective oxidation of sulfides to sulfones using Af-methylmorpholine IV-oxide (NMP) and a catalytic perruthenatc was found to be also applicable in the presence of isolated or allylic double bonds [115]. 

The H0F-CH3CN complex readily oxidizes sulfides to sulfones.120 The electrophilic nature was confirmed by an X o value (see Peroxides and Peracids for a discussion of Xgo) of 0.45. Examples include electron-deficient sulfides that cannot be oxidized to sulfone by any other method. 

Gokel, G.W., Gerdes, H.M., and Dishong, D.M., Sulfur heterocycles. 3. Heterogenous, phase-transfer, and acid catalyzed potassium permanganate oxidation of sulfides to sulfones and a survey of their carbon-13 nuclear magnetic resonance spectra, J. Org. Chem., 45, 3634, 1980. 

Inorganic peroxygens have also been used to oxidize sulfur centres, particularly sodium perborate, which is excellent for oxidizing electron-deficient sulfides to sulfones.412 Sodium perborate tetrahydrate has been used to stereo-specifically oxidize a-methylbenzylamine thiols in acetic acid.413 The use of organic peracids such as MCPBA was not found to be stereospecific for the above mentioned oxidation. 

Sodium percarbonate (PCS) can also be employed for the oxidation of sulfides to sulfones in acetonitrile assisted by ultrasound.415... 

A number of other oxidants which produce sulfones from sulfoxides are known, such as N02BF4, ° oxygen with Ir or Rh catalysts, ozone,KHSOs (Oxone) and K2S20s. Oxone is a highly chemoselective oxidant for the conversion of sulfides to sulfones without affecting hydroxy or al-kenic groups (equation 37). Similarly flavin (14) oxidizes aryl methyl sulfoxides to sulfones fairly selectively. ... 

Peroxyphthalic add, o-C,iH4(C02H)C03H, is obtained from phthalic anhydride and hydrogen peroxide [330] or sodium hydrogen peroxide [331] and is applied usually in ethereal solutions to epoxidations [330, 332], the Baeyer-Villiger reaction [333, 334], and oxidations of sulfides to sulfoxides [163, 335] and sulfones [336, 337]. The oxidation of sulfides to sulfones takes precedence over epoxidation, as evidenced by the fact that unsaturated ketone thioacetals are oxidized to unsaturated disulfones [337]. 

Sodium hypochlorite is used for the epoxidation of double bonds [659, 691] for the oxidation of primary alcohols to aldehydes [692], of secondary alcohols to ketones [693], and of primary amines to carbonyl compounds [692] for the conversion of benzylic halides into acids or ketones [690] for the oxidation of aromatic rings to quinones [694] and of sulfides to sulfones [695] and, especially, for the degradation of methyl ketones to carboxylic acids with one less carbon atom [655, 696, 697, 695, 699] and of a-amino acids to aldehydes with one less carbon [700]. Sodium hypochlorite is also used for the reoxidation of low-valence ruthenium compounds to ruthenium tetroxide in oxidations by ruthenium trichloride [701]. 

The spectrum of applications of potassium permanganate is very broad. This reagent is used for dehydrogenative coupling [570], hydrox-ylates tertiary carbons to form hydroxy compounds [550,831], hydroxylates double bonds to form vicinal diols [707, 296, 555, 577], oxidizes alkenes to a-diketones [560, 567], cleaves double bonds to form carbonyl compounds [840, 842, 552] or carboxylic acids [765, 841, 843, 845, 852, 869, 872, 873, 874], and converts acetylenes into dicarbonyl compounds [848, 856, 864] or carboxylic acids [843, 864], Aromatic rings are degraded to carboxylic acids [575, 576], and side chains in aromatic compounds are oxidized to ketones [566, 577] or carboxylic acids [503, 878, 879, 880, 881, 882, 555]. Primary alcohols [884] and aldehydes [749, 868, 555] are converted into carboxylic acids, secondary alcohols into ketones [749, 839, 844, 863, 865, 886, 887], ketones into keto acids [555, 559, 590] or acids [559, 597], ethers into esters [555], and amines into amides [854, 555] or imines [557], Aromatic amines are oxidized to nitro compounds [755, 559, 592], aliphatic nitro compounds to ketones [562, 567], sulfides to sulfones [846], selenides to selenones [525], and iodo compounds to iodoso compounds [595]. 

Cupric permanganate, Cu(Mn04)2 8H20, is commercially available and oxidizes primary alcohols and aldehydes to acids, secondary alcohols to ketones, and sulfides to sulfones in very high yields [894]. 

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