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Bisguanidinium dinuclear oxodiperoxomolybdosulfate ion pair-catalyzed enantioselective sulfoxidation

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ABSTRACT

Bg: Catalytic use of peroxomolybdate for asymmetric transformations has attracted increasing attention due to its catalytic properties and application in catalysis. Herein, we report chiral bisguanidinium dinuclear oxodiperoxomolybdosulfate []2+[(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− ion pair, as a catalyst for enantioselective sulfoxidation using aqueous H2O2 as the terminal oxidant. The ion pair catalyst is isolatable, stable and useful for the oxidation of a range of dialkyl sulfides. The practical utility was illustrated using a gram-scale synthesis of armodafinil, a commercial drug, with the catalyst generated in situ from 0.25 mol% of bisguanidinium and 2.5 mol% of Na2MoO4·2H2O. Structural characterization of this ion pair catalyst has been successfully achieved using single-crystal X-ray crystallography.

No MeSH data available.


Characterization of the anionic cluster [(μ-SO4)Mo2O2(μ-O2)2(O2)2] in (R,R)-1b.(a) ORTEP view of [(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− dianion in (R,R)-1b with the atom numbering scheme. (b) 95Mo NMR spectrum of (R,R)-1b in DMF-d7 (0.05 M, 22 °C).
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f5: Characterization of the anionic cluster [(μ-SO4)Mo2O2(μ-O2)2(O2)2] in (R,R)-1b.(a) ORTEP view of [(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− dianion in (R,R)-1b with the atom numbering scheme. (b) 95Mo NMR spectrum of (R,R)-1b in DMF-d7 (0.05 M, 22 °C).

Mentions: We attempted to identify the reactive catalytic species by mimicking the reaction conditions in the absence of sulfide substrate (Fig. 4). After a simple workup procedure, (R,R)-1b was isolated and a single crystal suitable for X-ray diffraction was grown by vapour diffusion of Et2O into a dimethylformamide (DMF) solution of (R,R)-1b. The structure of (R,R)-1b was fully characterized using X-ray analysis (Fig. 2b), 95Mo nuclear magnetic resonance (NMR) (Fig. 5b) and fourier transform-infrared spectroscopy (FT-IR) (Supplementary Fig. 2).


Bisguanidinium dinuclear oxodiperoxomolybdosulfate ion pair-catalyzed enantioselective sulfoxidation
Characterization of the anionic cluster [(μ-SO4)Mo2O2(μ-O2)2(O2)2] in (R,R)-1b.(a) ORTEP view of [(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− dianion in (R,R)-1b with the atom numbering scheme. (b) 95Mo NMR spectrum of (R,R)-1b in DMF-d7 (0.05 M, 22 °C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121337&req=5

f5: Characterization of the anionic cluster [(μ-SO4)Mo2O2(μ-O2)2(O2)2] in (R,R)-1b.(a) ORTEP view of [(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− dianion in (R,R)-1b with the atom numbering scheme. (b) 95Mo NMR spectrum of (R,R)-1b in DMF-d7 (0.05 M, 22 °C).
Mentions: We attempted to identify the reactive catalytic species by mimicking the reaction conditions in the absence of sulfide substrate (Fig. 4). After a simple workup procedure, (R,R)-1b was isolated and a single crystal suitable for X-ray diffraction was grown by vapour diffusion of Et2O into a dimethylformamide (DMF) solution of (R,R)-1b. The structure of (R,R)-1b was fully characterized using X-ray analysis (Fig. 2b), 95Mo nuclear magnetic resonance (NMR) (Fig. 5b) and fourier transform-infrared spectroscopy (FT-IR) (Supplementary Fig. 2).

View Article: PubMed Central - PubMed

ABSTRACT

Bg: Catalytic use of peroxomolybdate for asymmetric transformations has attracted increasing attention due to its catalytic properties and application in catalysis. Herein, we report chiral bisguanidinium dinuclear oxodiperoxomolybdosulfate []2+[(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− ion pair, as a catalyst for enantioselective sulfoxidation using aqueous H2O2 as the terminal oxidant. The ion pair catalyst is isolatable, stable and useful for the oxidation of a range of dialkyl sulfides. The practical utility was illustrated using a gram-scale synthesis of armodafinil, a commercial drug, with the catalyst generated in situ from 0.25 mol% of bisguanidinium and 2.5 mol% of Na2MoO4·2H2O. Structural characterization of this ion pair catalyst has been successfully achieved using single-crystal X-ray crystallography.

No MeSH data available.