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Asymmetric sulfoxidation of thioethers

Asymmetric sulfoxidation of thioethers has been achieved enzymatically, mostly using heme- or vanadium-based haloperoxidases as the bio-catalysts... [Pg.11]

Scheme 9. Solid-phase-bound ligands for the titanium-catalyzed asymmetric sulfoxidation of thioethers. Scheme 9. Solid-phase-bound ligands for the titanium-catalyzed asymmetric sulfoxidation of thioethers.
Scheme 23.16. Asymmetric sulfoxidation of thioethers with H2O2 mediated by dimeric Ti(salan) complexes. Scheme 23.16. Asymmetric sulfoxidation of thioethers with H2O2 mediated by dimeric Ti(salan) complexes.
Scheme 23.24. Asymmetric sulfoxidation of thioethers with O2 mediated by a Ru(III)salen complex. Scheme 23.24. Asymmetric sulfoxidation of thioethers with O2 mediated by a Ru(III)salen complex.
Scheme 23.25. Asymmetric sulfoxidation of thioethers with substoichiometric H2O2 mediated by a dimeric Fe(III) catalyst bearing a bipyridine ligand. Scheme 23.25. Asymmetric sulfoxidation of thioethers with substoichiometric H2O2 mediated by a dimeric Fe(III) catalyst bearing a bipyridine ligand.
Scarso, A. and Strukul, G. (2005). Asymmetric Sulfoxidation of Thioethers with Hydrogen Peroxide in Water Mediated by Platinum Chiral Catalyst, Adv. Synth. Catal., 347, pp. 1227-1234. [Pg.761]

The asymmetric oxidation of thioethers as well as kinetic resolution of sulfoxides with 30% H2O2 catalyzed by a stable, recyclable and commercially avialable solid WO3 catalyst provides a simple and effective procedure for the preparation of chiral sulfoxides in good enantimeric purity. The procedure is very easy to perform. [Pg.293]

Enantiomerically pure sulfoxides are important intermediates in organic synthesis (21) and quite a number of pharmaceuticals and other biologically active compounds harbor a chiral sulfoxide unit (22). With respect to oxidation catalysis, enantiomerically enriched sulfoxides can either be accessed by asymmetric sulfoxidation of prochiral thioethers (Scheme 7, path a), or by kinetic resolution of racemic sulfoxides (Scheme 7, path b). For the latter purpose, enantio-specific oxidation of one sulfoxide enantiomer to the sul-fone, followed by separation, is the method of choice. [Pg.10]

Scheme 8. Highly efficient and selective modular ligands for the vanadium-catalyzed asymmetric sulfoxidation of prochiral thioethers. Scheme 8. Highly efficient and selective modular ligands for the vanadium-catalyzed asymmetric sulfoxidation of prochiral thioethers.
Scheme 19. Directed evolution of a cyclohexanone monooxygenase for the asymmetric sulfoxidation of a prochiral thioether. Scheme 19. Directed evolution of a cyclohexanone monooxygenase for the asymmetric sulfoxidation of a prochiral thioether.
Scheme 23.15. Asymmetric sulfoxidation of aryknethyl thioethers and mediated by aTi(IV) catalyst bearing an atropoisomeric salen ligand. Scheme 23.15. Asymmetric sulfoxidation of aryknethyl thioethers and mediated by aTi(IV) catalyst bearing an atropoisomeric salen ligand.
Chiral sulfoxides have emerged as versatile building blocks and chiral auxiliaries in the asymmetric synthesis of pharmaceutical products. The asymmetric oxidation of prochiral sulfides with chiral metal complexes has become one of the most effective routes to obtain these chiral sulfoxides.We have recently developed a new heterogeneous catalytic system (WO3-30% H2O2) which efficiently catalyzes both the asymmetric oxidation of a variety of thioethers (1) and the kinetic resolution of racemic sulfoxides (3), when used in the presence of cinchona alkaloids such as hydroquinidine 2,5-diphenyl-4,6-pyrimidinediyl diether [(DHQD)2-PYR], Optically active sulfoxides (2) are produced in high yields and with good enantioselectivities (Figure 9.3). ... [Pg.288]

Reduction of sulfoxides to thioethers.1 Use of hydrogen halides for this reduction was first reported in 1909 and is still a viable method. This reduction has assumed importance since chiral sulfinyl groups are valuable in asymmetric syntheses and are eliminated in two steps reduction to the ether followed by catalytic hydrogenation or metal/ammonia reduction. The first step can now be carried out with several reagents, as shown by this comprehensive review (349 references). [Pg.166]

Another class of peroxidases which can perform asymmetric sulfoxidations, and which have the advantage of inherently higher stabilities because of their non-heme nature, are the vanadium peroxidases. It was shown that vanadium bromoperoxidase from Ascophyllum nodosum mediates the production of (R)-methyl phenyl sulfoxide with a high 91% enantiomeric excess from the corresponding sulfide with H202 [38]. The turnover frequency of the reaction was found to be around 1 min-1. In addition this enzyme was found to catalyse the sulfoxidation of racemic, non-aromatic cyclic thioethers with high kinetic resolution [309]. [Pg.208]

Very recently, Fedin, Kim and colleagues synthesized a homochiral metalorganic polymeric material, [Zn2(bdc)(L-lac)(dmf)] (DMF) (36), by using a one-pot solvothermal reaction of Zn(NO3)2, L-lactic acid (L-H2lac) and 1,4-benzenedicarbox-ylic acid (H2bdc) in DMF [53]. This 3-D homochiral microporous framework exhibited permanent porosity and enantioselective host-guest sorption properties towards several substituted thioether oxides. Although 36 could catalyze the oxidation of thioethers to sulfoxides with size and chemoselectivity, no asymmetric induction was observed. [Pg.351]

The material 6 showed a remarkable catalytic activity in the oxidation of thioethers 13 to sulfoxides 14 by urea hydroperoxide (UHP) or H O (Scheme 2). Although the conversion and selectivity (for 14 over 15, >90%) was reasonable with UHP for the substrates with smaller substituents, 13a and 13b, the ones with bulkier substrates 13c and 13d failed to produce any measurable conversion. The conversion increases to 100% by changing UHP with H O. The catalytic activity of 6 for selective sulfoxidation remains similar even after 30 cycles. Despite the fact that no asymmetric induction was found in the catalytic sulfoxidations, enantioen-riched sulfoxides were obtained by enantioselective sorption of the resulting racemic mixture by the chiral pores of 6, which occured simultaneously with the catalytic process. Thus, after catalytic oxidation of 13a, (5)-14a was preferentially absorbed by the pore of 6 leaving exactly equal amount of the excess ) -enantiomer in the solution phase (-20% ee). The combination of high catalytic activity and enantioselective sorption property of 6 provides a unique opportunity to device a one-step process to produce enantioenriched products. [Pg.136]

The asymmetric oxidation of sulfides represents a straightforward access to chiral sulfoxides that are useful compounds for asymmetric synthesis as chiral auxiliaries and also for the synthesis of biologically active molecules. Among the different methods to perform these reactions, titanium-mediated thioether oxidation is one of the most attractive. Indeed, Kagan ° and Modena independently showed that the use of chiral titanium complexes derived from Sharpless reagent allows the asymmetric oxidation of prochiral sulfides (Scheme 7.6). [Pg.143]

The asymmetric monooxidation of a thioether leading to a chiral sulfoxide resembles a desymmetrization of a prochiral substrate and is therefore of high synthetic value. [Pg.190]

It should finally be mentioned that asymmetric and metal-free sulfoxidation can also be achieved by use of flavinium (84) [131] or simpler chiral iminium cations (85) as catalysts [132] (Scheme 10.18). For the axially chiral flavinophane 84 enantiomeric excesses up to 65% were reported by Toda et al. (for methyl p-tolyl sulfide as substrate), at typical catalyst loadings of ca. 10 mol% (relative to the thioether). The same substrate gave the sulfoxide with 32% ee when the iminium cation 85 was used [132],... [Pg.305]

Nitrones were the first as well as the most widely used dipoles in asymmetric cycloadditions. The first report on the use of enantiomerically pure vinylsulf-oxides as dipolarophiles was due to Koizumi et al. [153], who described in 1982 the reaction of (-R)-vinyl p-tolyl sulfoxide 1 with acyclic nitrones 191. The reactions required 20 h in refluxing benzene to be completed, yielding a mixture of only two compounds, 192 and 193 (Scheme 91). They exhibited identical endo or exo stereochemistry (which was not unequivocally assigned), deduced from the fact that their reduction yielded enantiomeric thioethers. The major component, 192, exhibits (S) configuration at C-3, determined by chemical correlation. The authors claim this paper [153] to be the first example of 1,3-dipolar cycloaddition using chiral dipolarophiles. [Pg.98]

Major interest has been expressed in the synthesis of chiral sulfoxides since the early 1980s, when it was discovered that chiral sulfoxides are efficient chiral auxiliaries that are able to bring about important asymmetric transformations [22]. Sulfoxides are also constituents of important drugs (e.g., omeprazole (Losec , Priso-lec )) [23]. There is a plethora of routes of access to enantioenriched sulfoxides, and many involve metal-catalyzed asymmetric oxidations [24]. Examples of ruthenium metal-based syntheses of sulfoxides are scarce, presumably due to the tendency of sulfur atoms to bind irreversibly to a ruthenium center. Schenk et al. reported a dia-stereoselective oxidation of Lewis acidic Ru-coordinated thioethers with dimethyl-dioxirane (DMD) (Scheme 10.16) [25[. Coordination of the prochiral thioether to the metal is followed by diastereoselective oxygen transfer from DMD in high yield. The... [Pg.264]


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See also in sourсe #XX -- [ Pg.2 , Pg.10 , Pg.11 , Pg.13 ]




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Asymmetric sulfoxidation

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Sulfoxides thioethers

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