Sulfoxides, preparation from sulfides

Sulfinic esters, aromatic, by oxidation of disulfides in alcohols, 46, 64 Sulfonation ot d,l camphor to d,l-10-camphorsulfomc acid, 45,12 Sulfoxides, table of examples of preparation from sulfides with sodium metapenodate, 46,79 Sulfur dioxide, reaction with styrene phosphorus pentachlonde to give styrylphosphomc diclilonde, 46,... 

The use of the Julia-Lythgoe olefination with cyclopropylsulfones and cyclopropylsulfoxides for the synthesis of alkylidenecyclopropanes was reported by Bernard and co-workers. The adduct sulfide 60, prepared from sulfide 58, was oxidized to sulfone 61 and sulfoxide 64 by controlling oxidation temperature. Both intermediate 61 and 64 can be further converted to trisubstituted alkene 63 under different reductive condition. 

Sulfones and sulfoxides (145) are obtained usually from the corresponding sulfide by oxidation (Scheme 75) (341). though some of them were prepared from a halothiazole and metal sulfinate (342). 2-Amino-5-acetamidophenylsulfonylthiazole has been prepared by direct heterocycli-zation (343. 344). 

The oxidation of sulfides to sulfoxides (1 eq. of oxidant) and sulfones (2 eq. of oxidant) is possible in the absence of a catalyst by employing the perhydrate prepared from hexafluoroacetone or 2-hydroperoxy-l,l,l-trifluoropropan-2-ol as reported by Ganeshpure and Adam (Scheme 99 f°. The reaction is highly chemoselective and sulfoxidation occurs in the presence of double bonds and amine functions, which were not oxidized. With one equivalent of the a-hydroxyhydroperoxide, diphenyl sulfide was selectively transformed to the sulfoxide in quantitative yield and with two equivalents of oxidant the corresponding sulfone was quantitatively obtained. 2-Hydroperoxy-l,l,l-fluoropropan-2-ol as an electrophilic oxidant oxidizes thianthrene-5-oxide almost exclusively to the corresponding cw-disulfoxide, although low conversions were observed (15%) (Scheme 99). Deprotonation of this oxidant with sodium carbonate in methanol leads to a peroxo anion, which is a nucleophilic oxidant and oxidizes thianthrene-5-oxide preferentially to the sulfone. 

In general, sulfoximines are accessible by various routes, and most of them involve sulfur oxidation/imination sequences. For example, enantiopure 9 is commonly prepared starting from sulfide 10, which is oxidized with hydrogen peroxide (under acidic conditions) giving sulfoxide 11 (Scheme 2.1.1.1). Subsequent imina-tion of 11 with a mixture of sodium azide and sulfuric acid affords sulfoximine 9 as a racemate. Enantiomer resolution can then be achieved with camphorsul-fonic acid, leading to both enantiomers of 9 with high efficiency [15]. Alternatively, many sulfoximine syntheses start from enantiopure sulfoxides [16, 17], which can be stereospecifically iminated with 0-mesitylenesulfonylhydroxyl-amine (MSH) [18], as shown for the synthesis of sulfoximine (1 )-13 in Scheme 2.I.I.2. 

Uemura reported a highly enantioselective oxidation of sulfides to sulfoxides using a chiral titanium complex prepared from chiral BINOL and Ti(0-i-Pr)4, and this reaction exhibits a remarkable asymmetric amplification (Scheme 9.15) [33]. 

Remarkably, there is a noticeable lack of general methods for the asymmetric preparation of chiral sulfoxides from sulfides. The most satisfactory method would be a generally applicable enantioselective sulfoxidation reaction which would allow the preparation of sulfoxides from any prochiral sulfide with high ee s and in which the sulfoxide would be amenable to enantioselective preparation in both senses. 

Organic hydroperoxides are generally used for the preparation of sulfoxides from sulfides, - while sulfones can be obtained in neutral organic solvents in the presence of metal catalysts such as V, Mo and Ti oxides at 50-70 C. Two polymer-supported reagents which involve peroxy acid groups and bound hypervalent vanadium(V) and molybdenum(VI) compounds have been developed for facile oxidation of sulfoxides to sulfones. 

This ylide chemistry is treated in a number of monographs and reviews. The formation and properties of 77 and 78 were first dealt with by Corey et al. Reactive ylides are prepared from dialkyl sulfide and dialkyl sulfoxide in a non-aqueous medium. The solvent for the epoxidation reaction may be an aqueous basic solution. No side-reactions occur in a two-phase system or under the more recent phase-transfer conditions. ... 

Dioxiranes, prepared from acetone and other aliphatic ketones by treatment with Oxone, can accomplish oxidations that are usually not achieved by Oxone itself [210, 211], Dioxiranes can be isolated by vacuum codistillation with the respective ketones [210], or else, they may be formed in situ and applied in the same reaction vessel [210, 211]. Examples of the applications of dioxiranes are epoxidations 210] and the oxidation of primary amines to nitro compounds [211], of tertiary amines to amine oxides [210], and of sulfides to sulfoxides [210] (equation 12). 

A still unresolved problem is the structure of the often used adducts from phosphorus trihalides and carboxylic acid amides, which might be described by the formulae (8) or (9). With the aid of in situ generated adducts of acid amides and PX3 amidines, isonitriles, quinazolinones, alkyl chlorides, aminomethylenediphosphonic acids, carbamoyl halides, triformylaminomethane, 1,3,4-oxadia-zoles, sulfides (from sulfoxides), nitriles (from primary nitro compounds)" and bromoqui-nolines (from methoxyquinolines)" have been prepared. 

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