Transition Metal Catalyzed Asymmetric Oxidation of Sulfides

Bryliakov, Konstantin P.; Talsi, Evgenii P.

doi:10.2174/138527208783743660

Cited by 42 publications

(18 citation statements)

References 133 publications

(168 reference statements)

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“…Solvents were distilled prior to use. 1 H (300 MHz), 1 H (400 MHz) and 13 The Sodium D line (589 nm) was used unless otherwise indicated. Samples were analysed in a 1 mL dual-walled thermostatted glass cell of pathlength 10 cm.…”

Section: Methodsmentioning

confidence: 99%

“…5o, 5r, 5q, 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6i, 6j, 6k, 6l, 6m, 6n, 6o, 6p, 6q, 6r, 2d, 4, 13, 14 and 15. 13 C NMR spectra are available for compounds 5o, 5r, 5q, 6h, 6i, 4, 13, 14 and 15. HPLC data are available for sulfoxides 6i and 6h.…”

Section: Acknowledgementsmentioning

confidence: 99%

“…The Kagan system is limited by its sensitivity to atmospheric moisture, low turnover numbers and it utilises a complex and expensive catalytic system. 13 Although the Bolm procedure is robust and operationally straightforward the use of vanadium is not advantageous since vanadium is known to exert toxic, mutagenic and genotoxic effects on a variety of biological systems. 14 Copper has received relatively little attention in metal-catalyzed asymmetric sulfoxidation.…”

Section: Introductionmentioning

confidence: 99%

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Copper-Catalyzed Asymmetric Oxidation of Sulfides

2012

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Access to the full text of the published version may require a subscription. Rights AbstractCopper-catalyzed asymmetric sulfoxidation of aryl benzyl and aryl alkyl sulfides, using aqueous hydrogen peroxide as oxidant, has been investigated. A relationship between the steric effects of the sulfide substituents and the enantioselectivity of the oxidation has been observed, with up to 93% ee for 2-naphthylmethyl phenyl sulfoxide, in modest yield in this instance (up to 30%). The influence of variation of solvent and ligand structure were examined and the optimised conditions were then used to oxidise a number of aryl alkyl and aryl benzyl sulfides, producing sulfoxides in excellent yields in most cases (up to 92%), and good enantiopurities in certain cases (up to 84% ee).

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Section: Methodsmentioning

confidence: 99%

Section: Acknowledgementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Copper-Catalyzed Asymmetric Oxidation of Sulfides

2012

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“…A comprehension of the mechanistic pathways operating in the metal catalysed version of such process is clearly fundamental in order to obtain effective and selective procedure. Reviews, concerning the synthetic aspects of enantioselective synthesis of sulfoxides, appeared recently [40,41]. In those papers the very many chiral ligands used in the vanadium catalysed version of the oxidation with peroxides, mainly variously substituted Schiff bases [42], are collected and the structural features are also discussed.…”

Section: Oxidation Of Nucleophilic Substratesmentioning

confidence: 99%

Mechanistic aspects of vanadium catalysed oxidations with peroxides

Conte

Coletti

Licini

et al. 2011

Coordination Chemistry Reviews

204

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“…[4] Accordingly, the esomeprazole process has become an important source of inspiration and reference point for academic research to develop new efficient asymmetric catalytic methods relevant for the pharmaceutical industry and for the synthesis of specialized chemicals. Optically active sulfoxides, [5][6][7][8][9][10] in general, represent an important class of pharmaceuticals and drug intermediates. [11] They often play an important role as therapeutic agents, such as anti-ulcer (proton pump inhibitors), [12][13][14][15][16] antibacterial, anti-atherosclerotic, [17][18][19] anthelmintic, [20] Adv.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of the Asymmetric Sulfoxidation in the Esomeprazole Process: Effects of the Imidazole Backbone for the Enantioselection

2009

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Abstract:The asymmetric sulfoxidation reaction of imidazole-based prochiral sulfides was studied to explore the mechanistic details of the highly efficient esomeprazole process, which is one of the few industrial scale catalytic asymmetric procedures. The synthetic studies revealed that the smallest subunit governing the selectivity in the esomeprazole process is an imidazole ring. Thus, by using the esomeprazole procedure methyl imidazole sulfide could be oxidized as efficiently as its several functionalized derivatives, including pyrmetazol. However, alkylation of the imidazole nitrogen led to a major drop of the enantioselectivity. Our atmospheric pressure chemical ionization-mass spectrometry (APCI/MS) studies indicate that addition of small amounts of water to the reaction mixture facilitates the formation of mononuclear titanium species, which are the active catalytic intermediates of the selective oxidation reaction. One of the most important features of the esomeprazole procedure is that amine additives increase the enantioselectivity of the oxidation process. The NMR studies of the presumed reaction intermediates show that under catalytic conditions the amines are able to coordinate to titanium and dissociate the coordinated imidazole substrate. The density functional theory (DFT) modelling studies provided new insights in the mechanism of the asymmetric induction. It was found that the oxidation requires a lower activation energy if the imidazole sulfide precursor does not coordinate to titanium. Two possible reaction paths were explored for this out of sphere oxidation mechanism. The most important interaction governing the enantioselection is hydrogen bonding between the N À H of the imidazole ring and the chiral tartrate ligand on titanium. Furthermore, the oxidation reaction imposes an important structural constraint to the TS structure involving a linear arrangement of the peroxide oxygens and the sulfur atom. This constraint and the N coordination of imidazole leads to a very strained structure for the inner sphere mechanism of the oxidation, which leads to a much higher activation barrier than the corresponding out of sphere process, and therefore it is unlikely.

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Transition Metal Catalyzed Asymmetric Oxidation of Sulfides

Cited by 42 publications

References 133 publications

Copper-Catalyzed Asymmetric Oxidation of Sulfides

Copper-Catalyzed Asymmetric Oxidation of Sulfides

Mechanistic aspects of vanadium catalysed oxidations with peroxides

Mechanism of the Asymmetric Sulfoxidation in the Esomeprazole Process: Effects of the Imidazole Backbone for the Enantioselection

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