Chirality cyclic sulfides

When a prochiral sulfide is submitted to the oxidation by DMD or TFD, the corresponding racemic sulfoxide is produced, whereas in the case of a chiral sulfide, diastereoselective oxidation is feasible. For example, a good diastereoselectivity was obtained with the chiral cyclic disulfide in equation 21. ... 

Chiral sulfoxidation of cyclic sulfides 88CRV473 90MI60. 

In an asymmetric version of the Corey oxirane synthesis, aryl aldehydes are reacted with benzyl bromide in the presence of the cyclic sulfide (cat ) derived from D-camphor as a chiral catalyst to give 1,2-diaryloxiranes with high stereoselectivities [15], for example ... 

CHMO.. has been used in the diastereoselective oxidation of different p-hydroxy sulfides to the corresponding chiral p-hydroxy sulfoxides. Chiral p-hydroxy sulfoxides represent interesting compounds used as chiral auxiliaries in asymmetric synthesis, asymmetric ligands, or as building blocks for the synthesis of cyclic sulfides, benzoxathiepines, allylic alcohols, or leukotrienes [27]. The sulfoxidation of these substrates is a kinetic resolution, in which both the sulfide and the sulfoxide can be obtained in chiral form. Oxidation of the cyclohexyl derivative (Table 6.1, entry 2) by a semipurified preparation of in the presence of the enzymatic... 

C-chiral racemic y-hydroxy sulfides were also resolved using PEL under kinetic resolution conditions. The products were transformed into optically active 3-(alkanesulfonyloxy)thiolane salts (Scheme 1). Similarly, 1,2-cyclic sulfite glycerol derivatives cis and trans) were resolved into enantiomers via a Pseudomonas cepacia-catalysed acylation with vinyl butyrate. The E values depended on the solvent used and varied from 2 to 26. ... 

In the design of chiral sulfides for sulfur ylide-mediated asymmetric epoxidation of aldehydes, two factors are important. First, a single sulfur ylide should be produced. Otherwise, the diastereomeric sulfur ylides may react with aldehydes in different ways and thus cause a drop in stereoselectivity. This may be achieved by choosing a rigid cyclic structure to make one of the lone pairs more accessible than the other. Second, the structure should be amenable to structural modification in order to study the electronic and steric effects of the sulfur on the enantioselectivity of the epoxidation reaction. 

Chiral Davis oxaziridines allow the oxidation of phosphonates to a-hydroxy-phosphonates in good ee with apparently wide generality and with a sense of induction that is well controlled by the chirality of the reagent used.109 mCPBA oxidation of a bi-cyclic e do-camphorylsulfonylimine surprisingly resulted in an exo-camphorylsulfonyl-oxaziridine, whereas all other camphorylsulfonylimines resulted only in endo-oxaziiidines.110 Asymmetric oxidation of sulfides to sulfoxides and the a-hydroxylation of enolates were predicted by models in which steric interactions are minimized. 

The Morita-Baylis-Hillman reaction of chiral glyoxylic acid derivatives with cyclic a,/ -unsaturated ketones proceeded under the catalytic influence of dimethyl sulfide in the presence of titanium tetrachloride [27]. The adducts were obtained with high diastereomeric excess (>95% de) and typical yields around 80%. 

The typical S-oxidation with BVMOs allows the formation of chiral sulfoxides from organic sulfides. This oxidation has received much interest in organic chemistry due to its use in the synthesis of enantiomerically enriched materials as chiral auxiliaries or directly as biologically active ingredients. This reaction has been studied extensively with CHMO from Adnetohacter showing high enantioselectivi-ties in the sulfoxidation of alkyl aryl sulfides, disulfides, dialkyl sulfides, and cychc and acyclic 1,3-dithioacetals [90]. CHMO also catalyzes the enantioselective oxida-hon of organic cyclic sulfites to sulfates [91]. 

This reaction was carried out on cyclic and acyclic allylic carbonates. The 5-allylic thiocarbamate products were hydrolyzed to the corresponding thiol or reacted with 2-chloropyrimidine in the presence of potassium hydroxide to provide the sulfide without any loss in stereochemical purity for either example. a-Acetoxysulfones can be regarded as acid-stable, but base-labile, chiral aldehyde equivalents. These can be accessed through the palladium(0)-cataly zed reaction of geminal esters with sodium benzenesulfinate under phase-transfer conditions (eq 12). ... 

Introduction of an alkylthio group on the allene system increased the reactivity of the allene moiety in [2 + 2] cycloaddition reactions. It proved possible to conduct reactions of this allene at much lower temperatures. By adding Lewis acids, the reaction temperature could be decreased even more, as was illustrated by the Lewis acid catalyzed [2-1-2] cycioadditions of l-trimethylsilyl-l-methylthio-l,2-propadiene with a variety of electron-poor alkenes, including cyclic and non-cyclic enones, acrylates, methyl fumarate and acrylonitrile. When a chiral diol 21 based titanium catalyst was employed, the [2-1-2] cycloaddition reactions of /-acryloyl-l,3-oxazolidin-2-ones 17a and 17b with allenyl sulfides 18 yielded methylenecyclobutanes 19 and 20 with high optical purities (equation The highest yields were obtained with electron-poor allenophile 17b. 

The stereoselective ketene-Claisen rearrangements of optically active cyclic allyl sulfides, which can be run slightly above room temperature, result in chirality transfer from a C-S bond to a C-C bond. Due to the mild reaction conditions, the yields often prove to be superior to the oxygen counterparts and result in nearly complete chiral transmission. No loss of optical purity is observed during the dechlorination step, e.g., rearrangement of 1 and 2 and subsequent dechlorination to give 3 and 4429. 

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