- Oxygenation of Organoboronic Acids by a Nonheme Iron(II) Complex: Mimicking Boronic Acid Monooxygenase Activity
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Phenolic compounds are important intermediates in the bacterial biodegradation of aromatic compounds in the soil. An Arthrobacter sp. strain has been shown to exhibit boronic acid monooxygenase activity through the conversion of different substituted phenylboronic acids to the corresponding phenols using dioxygen. While a number of methods have been reported to cleave the C-B bonds of organoboronic acids, there is no report on biomimetic iron complex exhibiting this activity using dioxygen as the oxidant. In that direction, we have investigated the reactivity of a nucleophilic iron-oxygen oxidant, generated upon oxidative decarboxylation of an iron(II)-benzilate complex [(TpPh2)FeII(benzilate)] (TpPh2 = hydrotris(3,5-diphenyl-pyrazol-1-yl)borate), toward organoboronic acids. The oxidant converts different aryl/alkylboronic acids to the corresponding oxygenated products with the incorporation of one oxygen atom from dioxygen. This method represents an efficient protocol for the oxygenation of boronic acids with dioxygen as the terminal oxidant.
- Chatterjee, Sayanti,Paine, Tapan Kanti
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supporting information
p. 9727 - 9732
(2015/11/03)
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- Enantioselective syntheses of sulfoxides in octahedral ruthenium(II) complexes via a chiral-at-metal strategy
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The preparation of chiral 2-(alkylsulfinyl)phenol compounds by enantioselective coordination-oxidation of the thioether ruthenium complexes with a chiral-at-metal strategy has been developed. The enantiomerically pure sulfoxide complexes δ-[Ru(bpy)2{(R)-LO-R}](PF6) (bpy is 2,2′-bipyridine, HLO-R is 2-(alkylsulfinyl)phenol, R = Me (δ-1a), Et (δ-2a), iPr (δ-3a), Bn (δ-4a), and Nap (δ-5a)) and δ-[Ru(bpy)2{(S)-LO-R}](PF6) (R = Me (δ-1a), Et (δ-2a), iPr (δ-3a), Bn (δ-4a), and Nap (δ-5a)) have been synthesized by the reaction of δ-[Ru(bpy)2(py)2]2+ or δ-[Ru(bpy)2(py)2]2+ with the prochiral thioether ligands 2-(alkylthio)phenol (HL-R), followed by enantioselective oxidation with m-CPBA as oxidant. The X-ray crystallography was used to verify the stereochemistry of ruthenium complexes and sulfur atoms. The configurations of the ruthenium complexes are stable during the coordination and oxidation reactions. Moreover, the chiral sulfoxide ligands are enantioselectively generated by controlling of the configuration of ruthenium centers in the course of oxidation reaction. That is, the δ configuration at the ruthenium center generates the S sulfoxide ligand; on the contrary, the δ configuration of the ruthenium complex originates the R sulfoxide ligand. Acidolysis of δ-[Ru(bpy)2{(R)-LO-R}](PF6) and δ-[Ru(bpy)2{(S)-LO-R}](PF6) complexes in the presence of TFA-MeCN afforded the chiral ligands (R)-HLO-R and (S)-HLO-R in 96-99% ee values, respectively. Importantly, the chiral ruthenium complexes can be recycled as δ/δ-[Ru(bpy)2(MeCN)2](PF6)2 and reused in a next reaction cycle with complete retention of the configurations at ruthenium centers.
- Li, Zheng-Zheng,Wen, A-Hao,Yao, Su-Yang,Ye, Bao-Hui
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p. 2726 - 2733
(2015/03/30)
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- Stereoselective reductase-catalysed deoxygenation of sulfoxides in aerobic and anaerobic bacteria.
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Direct and indirect evidence, of unexpected stereoselective reductase-catalysed deoxygenations of sulfoxides, was found. The deoxygenations proceeded simultaneously, with the expected dioxygenase-catalysed asymmetric sulfoxidation of sulfides, during some biotransformations with the aerobic bacterium Pseudomonas putida UV4. Stereoselective reductase-catalysed asymmetric deoxygenation of racemic alkylaryl, dialkyl and phenolic sulfoxides was observed, without evidence of the reverse sulfoxidation reaction, using anaerobic bacterial strains. A purified dimethyl sulfoxide reductase, obtained from the intact cells of the anaerobic bacterium Citrobacter braakii DMSO 11, yielded, from the corresponding racemates, enantiopure alkylaryl sulfoxide and thiosulfinate samples.
- Boyd, Derek R,Sharma, Narain D,King, Alistair W T,Shepherd, Steven D,Allen, Christopher C R,Holt, Robert A,Luckarift, Heather R,Dalton, Howard
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p. 554 - 561
(2007/10/03)
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- Synthetic routes to polyheteroacenes: Characterization of a heterocyclic ladder polymer containing phenoxathiinium-type building blocks
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The synthetic routes to ladder polymers that consist of benzenetetrayl subunits with oxo and methylsulfonio linkages are described. As the key intermediate, poly(phenylene oxide)s having pendant methylsulfenyl groups are prepared by copper-catalyzed oxidative polymerization of the corresponding phenols with O2. The oxidation of the polymer with an equimolar amount of H2O2 in the presence of acetic acid effects the high-yielding conversion of methylsulfenyl to methylsulfinyl groups without the formation of the undesired methylsulfonyl groups. The superacidified condensation of the resulting polymer (Swern reaction of aryl sulfoxides) under dilution conditions induces the polymer-analogous intramolecular electrophilic ring-closing reaction of the hydroxymethylphenylsulfonium cation onto the adjacent benzene ring to yield the required ladder polymer, which has proved to be a semiconductor with an intrinsic electric conductivity of 2 × 10-5 S/cm. A comparison of the spectroscopic properties of the ladder polymer with those of the model compounds such as 5-methylphenoxathiinium triflate and phenoxathiin discloses π-electron delocalization over the methylsulfonio linkages, demonstrating the efficacy of the ladderization for p-π/d-π interactions in arylsulfonium moieties. This synthetic approach permits the thio and alkylsulfonio ladder linkages for a variety of phenyl ethers to form in high yields.
- Oyaizu, Kenichi,Mikami, Takefumi,Mitsuhashi, Fumio,Tsuchida, Eishun
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- Cisplatin Analogues with Sulfur Donor Ligands. (Ethylenediamine)platinum(II) Complexes with Ligands possessing a Sulfinyl or Sulfanyl Group linked to an Anionic Oxygen Donor Atom. Reactivity and Cytotoxicity
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Complexes of formula NO3, where en = ethylenediamine and L is a ligand in which a methylsulfinyl or methylsulfanyl group is linked to a carboxylate or phenolate moiety, have been synthesized and characterized by spectroscopic techniques.The ligand L is chelated to Pt via the sulfur and anionic oxygen atoms.The reactivities of these complexes towards nucleophiles have been investigated by 1H NMR spectroscopy; GMP is more reactive than Cl(-).The Pt-O bonds react more readily than the Pt-S bonds and, depending on the nature of L and Nu, the reactions either stop at the monosubstituted complex (with L monodentate and co-ordinated to Pt via the sulfur atom), or yield .The complex with L = 2-(methylsulfanyl)phenolate is unreactive.The stable monosubstituted products have been characterized.There is little correlation between the rates and the modes of reactivity of complex NO3 towards GMP and their cytotoxicities against the human ovarian carcinoma A2780 cell line.
- Pasini, Alessandro,Perego, Paola,Balconi, Massimo,Lupatini, Mauro
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p. 579 - 586
(2007/10/02)
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