- Effect of the Ligand Backbone on the Reactivity and Mechanistic Paradigm of Non-Heme Iron(IV)-Oxo during Olefin Epoxidation
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The oxygen atom transfer (OAT) reactivity of the non-heme [FeIV(2PyN2Q)(O)]2+ (2) containing the sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins. The ferryl-oxo complex 2 shows excellent OAT reactivity during epoxidations. The steric encumbrance and electronic effect of the ligand influence the mechanistic shuttle between OAT pathway I and isomerization pathway II (during the reaction stereo pure olefins), resulting in a mixture of cis-trans epoxide products. In contrast, the sterically less hindered and electronically different [FeIV(N4Py)(O)]2+ (1) provides only cis-stilbene epoxide. A Hammett study suggests the role of dominant inductive electronic along with minor resonance effect during electron transfer from olefin to 2 in the rate-limiting step. Additionally, a computational study supports the involvement of stepwise pathways during olefin epoxidation. The ferryl bend due to the bulkier ligand incorporation leads to destabilization of both (Formula presented.) and (Formula presented.) orbitals, leading to a very small quintet–triplet gap and enhanced reactivity for 2 compared to 1. Thus, the present study unveils the role of steric and electronic effects of the ligand towards mechanistic modification during olefin epoxidation.
- Biswas, Jyoti Prasad,Ansari, Mursaleem,Paik, Aniruddha,Sasmal, Sheuli,Paul, Sabarni,Rana, Sujoy,Rajaraman, Gopalan,Maiti, Debabrata
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supporting information
p. 14030 - 14039
(2021/05/11)
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- SUBSTITUTED PYRAZOLE COMPOUNDS AS TOLL RECEPTOR INHIBITORS
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Disclosed are compounds of Formula (I) N-oxides, or salts thereof, wherein G, A, R1, and R5 are defined herein. Also disclosed are methods of using such compounds as inhibitors of signaling through Toll-like receptor 7, or 8, or 9, and pharmaceutical compositions comprising such compounds. These compounds are useful in treating inflammatory and autoimmune diseases.
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Page/Page column 200-201
(2021/05/07)
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- Facile synthesis of libraries of functionalized cyclopropanes and oxiranes using ionic liquids – A new approach to the classical Corey-Chaykovsky reaction
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The potential of [PAIM][NTf2]/BMIM-ILs as a base/solvent in the Corey-Chaykovsky reaction is demonstrated by the facile synthesis of libraries of functionalized cyclopropanes from enones and oxiranes from aldehydes and ketones, at room temperature in respectable isolated yields. To demonstrate their application, the synthesized epoxides were employed as substrates for the synthesis of a library of 2,3-disubstituted quinolines, using [BMIM(SO3H)][OTf]/[BMIM][PF6] as a catalyst/solvent. The potential for recycling/reuse of the IL solvents was also explored.
- Malunavar, Shruti S.,Sutar, Suraj M.,Prabhala, Pavankumar,Savanur, Hemantkumar M.,Kalkhambkar, Rajesh G.,Aridoss, Gopalakrishnan,Laali, Kenneth K.
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supporting information
(2021/09/13)
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- The first crystallographically characterised ruthenium(vi) alkylimido porphyrin competent for aerobic epoxidation and hydrogen atom abstraction
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The syntheses of [RuVI(Por)(NAd)(O)] and [RuVI(2,6-F2-TPP)(NAd)2] have been described. [RuVI(2,6-F2-TPP)(NAd)(O)] capable of catalysing aerobic epoxidation of alkenes has been characterised by X-ray crystallography with RuNAd and RuO bond distances being 1.778(5) ? and 1.760(4) ? (∠O-Ru-NAd: 174.37(19)°), respectively. Its first reduction potential is 740 mV cathodically shifted from that of [RuVI(2,6-F2-TPP)(O)2].
- Chang, Xiao-Yong,Che, Chi-Ming,Shing, Ka-Pan,Wan, Qingyun
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supporting information
p. 4428 - 4431
(2020/05/05)
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- SO2F2-Mediated Epoxidation of Olefins with Hydrogen Peroxide
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An inexpensive, mild, and highly efficient epoxidation protocol has been developed involving bubbling SO2F2 gas into a solution of olefin, 30% aqueous hydrogen peroxide, and 4 N aqueous potassium carbonate in 1,4-dioxane at room temperature for 1 h with the formation of the corresponding epoxides in good to excellent yields. The novel SO2F2/H2O2/K2CO3 epoxidizing system is suitable to a variety of olefinic substrates including electron-rich and electron-deficient ones.
- Ai, Chengmei,Zhu, Fuyuan,Wang, Yanmei,Yan, Zhaohua,Lin, Sen
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p. 11928 - 11934
(2019/10/02)
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- In situ synthesis and encapsulation of copper phthalocyanine into MIL-101(Cr) and MIL-100(Fe) pores and investigation of their catalytic performance in the epoxidation of styrene
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In this work, copper phthalocyanine (CuPc) was encapsulated into mesocages of MIL-101(Cr) and MIL-100(Fe) by assembling CuPc's constitutional fractions using a deep eutectic solvent. The prepared materials, CuPc?MIL-101(Cr) and CuPc?MIL-100(Fe), were characterized by powder X-ray diffraction (PXRD), FT-IR, UV-vis and diffuse reflectance UV (DR-UV) spectroscopies, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ICP-OES spectrometry. The prepared materials were used as heterogeneous catalysts for catalytic epoxidation of styrene with molecular oxygen and also tert-butyl hydroperoxide (TBHP) as oxidants in acetonitrile as a solvent. The impact of MOFs and the role of the CuPc complex as the active species in the MOFs' cages in the epoxidation of styrene were investigated. Among the prepared catalysts, CuPc?MIL-101(Cr) showed the best performance. The heterogeneity of the catalysts was examined by a hot filtration test and ICP-OES of the filtrates after the reaction. Spent catalysts were analyzed by PXRD, FT-IR, UV-DRS, and TEM for reusability investigation and also to further explore the heterogeneous nature of the hybrid materials. Results showed that the prepared catalysts could be recycled and used for several concoctive times without a considerable drop in activity.
- Yeganeh, Ardeshir Dadgar,Amini, Mostafa M.,Safari, Nasser
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p. 1118 - 1131
(2019/11/03)
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- Biomimetic non-heme iron-catalyzed epoxidation of challenging terminal alkenes using aqueous H2O2 as an environmentally friendly oxidant
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Catalysis mediated by iron complexes is emerging as an eco-friendly and inexpensive option in comparison to traditional metal catalysis. The epoxidation of alkenes constitutes an attractive application of iron(III) catalysis, in which terminal olefins are challenging substrates. Herein, we describe our study on the design of biomimetic non-heme ligands for the in situ generation of iron(III) complexes and their evaluation as potential catalysts in epoxidation of terminal olefins. Since it is well-known that active sites of oxidases might involve imidazole fragment of histidine, various simple imidazole derivatives (seven compounds) were initially evaluated in order to find the best reaction conditions and to develop, subsequently, more elaborated amino acid-derived peptide-like chiral ligands (10 derivatives) for enantioselective epoxidations.
- Fingerhut, Anja,Vargas-Caporali, Jorge,Leyva-Ramírez, Marco Antonio,Juaristi, Eusebio,Tsogoeva, Svetlana B.
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- Preparing β-blocker (R)-Nifenalol based on enantioconvergent synthesis of (R)-p-nitrophenylglycols in continuous packed bed reactor with epoxide hydrolase
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An engineered epoxide hydrolase from Vigna radiate (VrEH2M263N) shows near-perfect enantioconvergence in single enzyme mediated hydrolysis of racemic p-nitrostyrene oxide (pNSO). To explore industrial potential of the promising biocatalyst, we tried to immobilize the VrEH2 variant by covalently linking onto a commercially available amino resin ECR8405F. Then a 5-mL packed bed reactor filled with the immobilized VrEH2M263N was connected with macroporous resin NKA-11 for in situ product adsorption, and the product (R)-p-nitrophenyl glycol (pNPG) was harvested by methanol elution, with 91% isolated yield and 97% ee. The continuous reactor was operated stably for more than 100 h with a space time yield of 20 g?L?1?h?1. Subsequently, the β-blocker (R)-Nifenalol was prepared by chemically synthesized from (R)-pNPG, affording the product in an overall yield of 61.3% (1.5 g) and an enantiopurity of 99.9% ee after recrystallization.
- Li, Fu-Long,Zheng, Yu-Cong,Li, Hao,Chen, Fei-Fei,Yu, Hui-Lei,Xu, Jian-He
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p. 1706 - 1710
(2019/01/30)
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- Tandem transfer hydrogenation-epoxidation of ketone substrates catalysed by alkene-tethered Ru(ii)-NHC complexes
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A series of nine cyclopentadienyl Ru(ii)-NHC complexes (1-9) have been synthesised by systematically varying the ligand and/or ligand substituents: η5-C5H4R′ (R′ = H, Me), EPh3 (E = P, As), NHC (Im, BIm), where NHC = Im(R)(R′) (R, R′ = Me, Bn, 4-NO2Bn, C2H4Ph, C4H7). Each of the Ru(ii)-NHC complexes features an N-alkenyl tether to attain bidentate NHC ligands. All complexes found application as catalysts in the tandem transfer hydrogenation and epoxidation reactions of carbonyl substrates. The catalytic activity of the complexes was shown to be similar, with efficiencies of up to 69% conversion after 18 hours and varying alcohol:epoxide selectivity for a variety of electronically diverse carbonyl substrates. Complex 3, with a nitro-containing substituent on the NHC ligand, was the only complex that showed preference for the alcohol product over the epoxide after 18 hours of reaction time.
- Malan, Frederick P.,Singleton, Eric,Van Rooyen, Petrus H.,Landman, Marilé
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supporting information
p. 8472 - 8481
(2019/06/14)
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- SUBSTITUTED INDOLE COMPOUNDS USEFUL AS TLR INHIBITORS
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Disclosed are compounds of Formula (I) N-oxides, or salts thereof, wherein G, A, R1, R5, and n are defined herein. Also disclosed are methods of using such compounds as inhibitors of signaling through Toll-like receptor 7, or 8, or 9, and pharmaceutical compositions comprising such compounds. These compounds are useful in treating inflammatory and autoimmune diseases.
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Page/Page column 144; 145
(2019/07/13)
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- Remarkable increase in the rate of the catalytic epoxidation of electron deficient styrenes through the addition of Sc(OTf)3 to the MnTMTACN catalyst
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The effect of Lewis acids on the catalytic activity of [Mn2(μ-O)3(TMTACN)2](PF6)2 in the epoxidation of styrenes using hydrogen peroxide as the oxidant has shown that the addition of Sc(OTf)3 at low catalytic loading results in a very significant increase in the efficiency of the catalyst and a reduction of the reaction time to only 3 minutes in most cases.
- Nodzewska, Aneta,Watkinson, Michael
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supporting information
p. 1461 - 1464
(2018/02/19)
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- Arylruthenium(III) Porphyrin-Catalyzed C-H Oxidation and Epoxidation at Room Temperature and [RuV(Por)(O)(Ph)] Intermediate by Spectroscopic Analysis and Density Functional Theory Calculations
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The development of highly active and selective metal catalysts for efficient oxidation of hydrocarbons and identification of the reactive intermediates in the oxidation catalysis are long-standing challenges. In the rapid hydrocarbon oxidation catalyzed by ruthenium(IV) and -(III) porphyrins, the putative Ru(V)-oxo intermediates remain elusive. Herein we report that arylruthenium(III) porphyrins are highly active catalysts for hydrocarbon oxidation. Using catalyst [RuIII(TDCPP)(Ph)(OEt2)] (H2TDCPP = 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin), the oxidation of C-H bonds of various hydrocarbons with oxidant m-CPBA at room temperature gave alcohols/ketones in up to 99% yield within 1 h; use of [nBu4N]IO4 as a mild alternative oxidant avoided formation of lactone from cyclic ketone in C-H oxidation, and the catalytic epoxidation with up to 99% yield and high selectivity (no aldehydes as side product) was accomplished within 5 min. UV-vis, electrospray ionization-mass spectrometry, resonance Raman, electron paramagnetic resonance, and kinetic measurements and density functional theory calculations lend evidence for the formation of Ru(V)-oxo intermediate [RuV(TDCPP)(O)(Ph)].
- Shing, Ka-Pan,Cao, Bei,Liu, Yungen,Lee, Hung Kay,Li, Ming-De,Phillips, David Lee,Chang, Xiao-Yong,Che, Chi-Ming
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supporting information
p. 7032 - 7042
(2018/06/12)
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- Mn(III)-Iodosylarene Porphyrins as an Active Oxidant in Oxidation Reactions: Synthesis, Characterization, and Reactivity Studies
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Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]+, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) at -60 °C and characterized using various spectroscopic methods. The [Mn(III)(ArIO)(Porp)]+ species were then investigated in the epoxidation of olefins under stoichiometric conditions. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. For example, cyclohexene oxide was formed exclusively with trace amounts of allylic oxidation products; cis- and trans-stilbenes were oxidized to the corresponding cis- and trans-stilbene oxides, respectively. In the catalytic epoxidation of cyclohexene by an electron-deficient Mn(III) porphyrin complex and sPhIO at low temperature (e.g., -60 °C), the Mn(III)-iodosylarene porphyrin species was evidenced as the active oxidant that effects the olefin epoxidation to give epoxide as the product. However, at high temperature (e.g., 0 °C) or in the case of using an electron-rich manganese(III) porphyrin catalyst, allylic oxidation products, along with cyclohexene oxide, were yielded, indicating that the active oxidant(s) was not the Mn(III)-iodosylarene adduct but probably high-valent Mn-oxo species in the catalytic reactions. We also report the conversion of the Mn(III)-iodosylarene porphyrins to high-valent Mn-oxo porphyrins under various conditions, such as at high temperature, with electron-rich porphyrin ligand, and in the presence of base (OH-). The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions. Other aspects, such as one oxidant versus multiple oxidants debate, also were discussed.
- Guo, Mian,Lee, Yong-Min,Seo, Mi Sook,Kwon, Yong-Ju,Li, Xiao-Xi,Ohta, Takehiro,Kim, Won-Suk,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo
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supporting information
p. 10232 - 10240
(2018/08/28)
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- Copper based coordination polymers based on metalloligands: Utilization as heterogeneous oxidation catalysts
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This work presents the synthesis and characterization of two Cu(ii)-based coordination polymers prepared by utilizing two different Co(iii)-based metalloligands offering appended arylcarboxylic acid groups. Both coordination polymers are three-dimensional in nature and present pores and channels filled with water molecules. Both coordination polymers function as heterogeneous catalysts for the epoxidation of various olefins using O2 while employing isobutyraldehyde as the coreductor and for peroxide-mediated oxidation of assorted benzyl alcohols. The catalytic results illustrate efficient oxidation reactions, whereas the hot-fltration test and leaching experiments indicate the true heterogeneous nature of the catalysis.
- Kumar, Gulshan,Hussain, Firasat,Gupta, Rajeev
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p. 16985 - 16994
(2019/01/03)
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- Catalytic Activity of Crystallographically Characterized Organic–Inorganic Hybrid Containing 1,5-Di-amino-pentane Tetrachloro Manganate with Perovskite Type Structure
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Abstract: Layered 2D organic–inorganic hybrid perovskite (OIHS) of the diammonium series, 1,5 di-aminepentane tetrachloro mangenate ([NH3–(CH2)5–NH3] MnCl4) was prepared by slow evaporation and reducing temperature method and characterized by single crystal X-ray diffraction analysis. Its structure consists of organic cation, [NH3(CH2)5NH3]+2 extended in a zigzag fashion and inorganic anion, [MnCl6]?2 where Mn2+ is coordinated by six Cl? ion in octahedral fashion. The organic and inorganic segments are alternately stacked along c-axis where inorganic layer is extended through corner-shared octahedra sandwiched by the di-aminopentane molecules. The layers (organic and inorganic) were connected to each other through N–HCl hydrogen bonds and van-der Waals interaction to build cation–anion–cation cohesion. The hybrid crystal had orthorhombic non-centrosymetric system having I212121 space group with unit cell parameters a = 7.1742(3) ?, b = 7.3817(3) ?, c = 23.9650(10) ?, V = 1269.13 ?3 and Z = 4. The hybrid exhibited excellent catalytic activity towards sulphide and alkene oxidation using aqueous H2O2 as an oxidant. Graphical Abstract: OIHS of the diammonium series [NH3–(CH2)5–NH3] MnCl4; 1,5 di-aminepentane tetrachloro mangenate were prepared by slow evaporation and temperature decrease method, characterized by single crystal X-ray diffraction. This complex exhibits excellent catalytic activity towards sulphide oxidation and alkene oxidation using aqueous H2O2 as an oxidant. [Figure not available: see fulltext.].
- Mondal, Paramita,Abdel-Aal, Seham Kamal,Das, Debasis,Islam, Sk Manirul
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p. 2332 - 2339
(2017/08/22)
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- Multistep Organic Transformations over Base-Rhodium/Diamine-Bifunctionalized Mesostructured Silica Nanoparticles
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The assembly of multiple catalytic functionalities within a single mesoporous silica as a catalyst for multistep enantioselective organic transformations in an environmentally friendly medium is a significant challenge in heterogeneous asymmetric catalysis. Herein, we took advantage of a BF4 ? anion hydrogen bonding strategy to anchor a chiral cationic rhodium/diamine complex within base-functionalized mesostructured silica nanoparticles conveniently to construct a bifunctional heterogeneous catalyst. The solid-state 13C NMR spectrum discloses the well-defined chiral Rh/diamine active species, and we used XRD, N2 adsorption–desorption, and electron microscopy to reveal the ordered mesostructure. The combination of bifunctionality in the silica nanoparticles enables two kinds of efficient enantioselective organic transformations with high yields and enantioselectivities, in which the asymmetric transfer hydrogenation of α-haloketones followed by epoxidation provides various chiral aryloxiranes, and the amination of α-haloketones with anilines followed by asymmetric transfer hydrogenation produces various β-amino alcohols. Furthermore, the catalyst can be recovered and recycled for seven times without a loss of catalytic activity, which is an attractive feature for multistep organic transformations in a sustainable benign process.
- Liao, Hang,Chou, Yajie,Wang, Yu,Zhang, Han,Cheng, Tanyu,Liu, Guohua
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p. 3197 - 3202
(2017/08/29)
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- Synthesis method for ethylene oxide derivative
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The invention discloses a synthesis method for an ethylene oxide derivative, which is an important intermediate for pesticides and medicines. The synthesis method includes the steps of performing a reaction to alkoxy phenyl sulfide (IV) with a methylation reagent at 70-90 DEG C to synthesize sulfonium salt (III); and then performing a reaction to the sulfonium salt (III) with a carbonyl compound (II) under alkali condition to generate the ethylene oxide derivative (I). In the method, sulfur ylide is synthesized by using the alkoxy phenyl sulfide, which is difficult to volatilize and is low in odor, instead of dimethyl sulfide, which is toxic and malodorous, in a conventional method, so that a problem of malodorous odor generated during production is solved from the source, and environment stress is greatly alleviated. Meanwhile, the alkoxy phenyl sulfide can be recycled, so that industrial cost is reduced and production efficiency is increased. The method is environment-friendly and high-effectively and can be used for synthesizing various ethylene oxide derivatives as pesticide and medicine intermediates.
- -
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Paragraph 0085; 0086; 0087
(2018/01/11)
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- Reductive activation of O2 by a bioinspired Fe complex for catalytic epoxidation reactions
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Aerobic epoxidation of olefins catalyzed by iron complexes without the use of a sacrificial coreductant is unknown. We report the reductive activation of O2 by a bioinspired [(bTAML)FeIII(H2O)]- (1) complex to catalyze the epoxidation of alkenes with TONs of up to 80. Spectroscopic and kinetic evidence indicates the involvement of FeV(O) as the active oxidant during the reaction.
- Singh, Kundan K.,Gupta, Sayam Sen
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supporting information
p. 5914 - 5917
(2017/07/11)
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- Spectroscopy and catalytic activity study of gold supported on barium titanate nanotubes for styrene epoxidation
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Gold (0.5-5 wt.%) supported on barium titanate nanotubes (Au/BaTNT) were prepared, characterized and for the first time, investigated as catalysts for selective oxidation of styrene with oxygen (O2 or H2 + O2) and peroxides (H2O2 or TBHP). Conversion of styrene enhanced when H2 was co-added to O2 in the reactions. Au/BaTNT activated O2 and H2 and produced H2O2 in situ for use in oxidations. Peroxides were found better oxidants than O2. At optimized conditions, styrene oxide selectivity of 80.1 wt.% at styrene conversion of 60.5 wt.% was achieved over Au(1 wt.%)/BaTNT using TBHP. Au particles (5.0-7.4 nm) were dispersed and decorated on the walls of BaTNT. They exhibited superior performance to the known Au catalysts in styrene oxidation. Reactive oxygen species formed during oxidation reactions were followed with in situ spectral characterizations (diffuse reflectance UV-vis and FT-Raman). Au/BaTNT was reusable in four recycles with little loss in catalytic activity.
- Nepak, Devadutta,Srinivas, Darbha
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- Mononuclear Nonheme High-Spin Iron(III)-Acylperoxo Complexes in Olefin Epoxidation and Alkane Hydroxylation Reactions
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Mononuclear nonheme high-spin iron(III)-acylperoxo complexes bearing an N-methylated cyclam ligand were synthesized, spectroscopically characterized, and investigated in olefin epoxidation and alkane hydroxylation reactions. In the epoxidation of olefins, epoxides were yielded as the major products with high stereo-, chemo-, and enantioselectivities; cis- and trans-stilbenes were oxidized to cis- and trans-stilbene oxides, respectively. In the epoxidation of cyclohexene, cyclohexene oxide was formed as the major product with a kinetic isotope effect (KIE) value of 1.0, indicating that nonheme iron(III)-acylperoxo complexes prefer C? - ?C epoxidation to allylic C-H bond activation. Olefin epoxidation by chiral iron(III)-acylperoxo complexes afforded epoxides with high enantioselectivity, suggesting that iron(III)-acylperoxo species, not high-valent iron-oxo species, are the epoxidizing agent. In alkane hydroxylation reactions, iron(III)-acylperoxo complexes hydroxylated C-H bonds as strong as those in cyclohexane at -40 °C, wherein (a) alcohols were yielded as the major products with high regio- and stereoselectivities, (b) activation of C-H bonds by the iron(III)-acylperoxo species was the rate-determining step with a large KIE value and good correlation between reaction rates and bond dissociation energies of alkanes, and (c) the oxygen atom in the alcohol product was from the iron(III)-acylperoxo species, not from molecular oxygen. In isotopically labeled water (H218O) experiments, incorporation of 18O from H218O into oxygenated products was not observed in the epoxidation and hydroxylation reactions. On the basis of mechanistic studies, we conclude that mononuclear nonheme high-spin iron(III)-acylperoxo complexes are strong oxidants capable of oxygenating hydrocarbons prior to their conversion into iron-oxo species via O-O bond cleavage.
- Wang, Bin,Lee, Yong-Min,Clémancey, Martin,Seo, Mi Sook,Sarangi, Ritimukta,Latour, Jean-Marc,Nam, Wonwoo
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supporting information
p. 2426 - 2436
(2016/03/05)
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- Exceedingly fast oxygen atom transfer to olefins via a catalytically competent nonheme iron species
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The reaction of [Fe(CF3SO3)2(PyNMe3)] with excess peracetic acid at -40 °C leads to the accumulation of a metastable compound that exists as a pair of electromeric species, [FeIII(OOAc)(PyNMe3)]2+ and [FeV(O)(OAc)(PyNMe3)]2+, in fast equilibrium. Stopped-flow UV/Vis analysis confirmed that oxygen atom transfer (OAT) from these electromeric species to olefinic substrates is exceedingly fast, forming epoxides with stereoretention. The impact of the electronic and steric properties of the substrate on the reaction rate could be elucidated, and the relative reactivities determined for the catalytic oxidations could be reproduced by kinetic studies. The observed fast reaction rates and high selectivities demonstrate that this metastable compound is a truly competent OAT intermediate of relevance for nonheme iron catalyzed epoxidations. A metastable nonheme iron-oxygen species undergoes exceedingly fast oxygen atom transfer (OAT) to olefins, providing epoxides with stereoretention. The reaction rates determined by stopped-flow UV/Vis analysis are in good agreement with the relative reactivities of different olefins, confirming that this compound is a competent OAT intermediate of relevance to nonheme iron catalyzed epoxidations.
- Serrano-Plana, Joan,Aguinaco, Almudena,Belda, Raquel,García-Espa?a, Enrique,Basallote, Manuel G.,Company, Anna,Costas, Miquel
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supporting information
p. 6310 - 6314
(2016/05/24)
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- Mononuclear Nonheme High-Spin (S=2) versus Intermediate-Spin (S=1) Iron(IV)–Oxo Complexes in Oxidation Reactions
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Mononuclear nonheme high-spin (S=2) iron(IV)–oxo species have been identified as the key intermediates responsible for the C?H bond activation of organic substrates in nonheme iron enzymatic reactions. Herein we report that the C?H bond activation of hydrocarbons by a synthetic mononuclear nonheme high-spin (S=2) iron(IV)–oxo complex occurs through an oxygen non-rebound mechanism, as previously demonstrated in the C?H bond activation by nonheme intermediate (S=1) iron(IV)–oxo complexes. We also report that C?H bond activation is preferred over C=C epoxidation in the oxidation of cyclohexene by the nonheme high-spin (HS) and intermediate-spin (IS) iron(IV)–oxo complexes, whereas the C=C double bond epoxidation becomes a preferred pathway in the oxidation of deuterated cyclohexene by the nonheme HS and IS iron(IV)–oxo complexes. In the epoxidation of styrene derivatives, the HS and IS iron(IV) oxo complexes are found to have similar electrophilic characters.
- Bae, Seong Hee,Seo, Mi Sook,Lee, Yong-Min,Cho, Kyung-Bin,Kim, Won-Suk,Nam, Wonwoo
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supporting information
p. 8027 - 8031
(2016/09/13)
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- Synthesis of enantiopure 1,2-azido and 1,2-amino alcohols via regio- and stereoselective ring-opening of enantiopure epoxides by sodium azide in hot water
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A practical and convenient method for the efficient and regio- and stereoselective ring-opening of enantiopure monosubstituted epoxides by sodium azide under hydrolytic conditions is reported. The ring-opening of enantiopure styryl and pyridyl (S)-epoxides by N3- in hot water takes place preferentially at the internal position with complete inversion of configuration to produce (R)-2-azido ethanols with up to 99% enantio- and regioselectivity, while the (S)-adamantyl oxirane provides mainly the (S)-1-adamantyl-2-azido ethanol in excellent yield. In general, 1,2-amino ethanols were obtained in high yield and excellent enantiopurity by the reduction of the chiral 1,2-azido ethanols with PPh3 in water/THF, and then converted into the Boc or acetamide derivatives.
- Wang, Hai-Yang,Huang, Kun,De Jesús, Melvin,Espinosa, Sandraliz,Pi?ero-Santiago, Luis E.,Barnes, Charles L.,Ortiz-Marciales, Margarita
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- Azidolysis of epoxides catalysed by the halohydrin dehalogenase from Arthrobacter sp. AD2 and a mutant with enhanced enantioselectivity: an (S)-selective HHDH
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Halohydrin dehalogenase from Arthrobacter sp. AD2 catalysed azidolysis of epoxides with high regioselectivity and low to moderate (S)-enantioselectivity (E?=?1–16). Mutation of the asparagine 178 to alanine (N178A) showed increased enantioselectivity towards styrene oxide derivatives and glycidyl ethers. Conversion of aromatic epoxides was catalysed by HheA-N178A with complete enantioselectivity, however the regioselectivity was reduced. As a result of the enzyme-catalysed reaction, enantiomerically pure (S)-β-azido alcohols and (R)-α-azido alcohols (ee???99%) were obtained.
- Mikleu?evi?, Ana,Primo?i?, Ines,Hrenar, Tomica,Salopek-Sondi, Branka,Tang, Lixia,Elenkov, Maja Majeri?
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p. 930 - 935
(2016/09/13)
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- Mononuclear Nonheme Iron(III)-Iodosylarene and High-Valent Iron-Oxo Complexes in Olefin Epoxidation Reactions
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High-spin iron(III)-iodosylarene complexes are highly reactive in the epoxidation of olefins, in which epoxides are formed as the major products with high stereospecificity and enantioselectivity. The reactivity of the iron(III)-iodosylarene intermediates is much greater than that of the corresponding iron(IV)-oxo complex in these reactions. The iron(III)-iodosylarene species - not high-valent iron(IV)-oxo and iron(V)-oxo species - are also shown to be the active oxidants in catalytic olefin epoxidation reactions. The present results are discussed in light of the long-standing controversy on the one oxidant versus multiple oxidants hypothesis in oxidation reactions. On active duty: High-spin iron(III)-iodosylarene complexes epoxidize olefins with high stereospecificity and enantioselectivity. The iron(III)-iodosylarene species, not high-valent iron(IV)- and iron(V)-oxo species, are the active oxidants in catalytic olefin epoxidation reactions. The present results resolve the long-standing controversy on the one oxidant versus multiple oxidants hypothesis in oxidation reactions.
- Wang, Bin,Lee, Yong-Min,Seo, Mi Sook,Nam, Wonwoo
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supporting information
p. 11740 - 11744
(2015/10/05)
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- Efficient and convenient epoxidation of alkenes to epoxides with H2O2 catalyzed by Co(OAc)2 in ionic liquid [C12py][PF6]
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A simple, efficient, and eco-friendly procedure for the epoxidation of alkenes to epoxides with H2O2 catalyzed by Co(OAc)2 in ionic liquid [C12py][PF6] has been developed. The reactions were carried out with alkene, Co(OAc)2 (0.1 mmol), [C12py][PF6] (10 mL), and H2O2 (30 %, 11 mmol) at room temperature for 2-6 h. This atom-economical protocol affords the target products in good to high yields (88-98 %). The products can be separated by a simple extraction with organic solvent, and the catalytic system can be recycled and reused without loss of catalytic activity. Graphical abstract: A simple, efficient, and eco-friendly procedure for the epoxidation of alkenes to epoxides with H2O2 catalyzed by Co(OAc)2 in ionic liquid [C12py][PF6] has been developed.[Figure not available: see fulltext.]
- Hu, Yu-Lin,Liu, Yi-Wen,Li, De-Jiang
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p. 2179 - 2184
(2015/10/19)
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- Mechanism of Oxygen Atom Transfer from FeV(O) to Olefins at Room Temperature
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In biological oxidations, the intermediate FeV(O)(OH) has been proposed to be the active species for catalyzing the epoxidation of alkenes by nonheme iron complexes. However, no study has been reported yet that elucidates the mechanism of direct O-atom transfer during the reaction of FeV(O) with alkenes to form the corresponding epoxide. For the first time, we study the mechanism of O-atom transfer to alkenes using the FeV(O) complex of biuret-modified Fe-TAML at room temperature. The second-order rate constant (k2) for the reaction of different alkenes with FeV(O) was determined under single-turnover conditions. An 8000-fold rate difference was found between electron-rich (4-methoxystyrene; k2 = 216 M-1 s-1) and electron-deficient (methyl trans-cinnamate; k2 = 0.03 M-1 s-1) substrates. This rate difference indicates the electrophilic character of FeV(O). The use of cis-stilbene as a mechanistic probe leads to the formation of both cis- and trans-stilbene epoxides (73:27). This suggests the formation of a radical intermediate, which would allow C-C bond rotation to yield both stereoisomers of stilbene-epoxide. Additionally, a Hammett ρ value of -0.56 was obtained for the para-substituted styrene derivatives. Detailed DFT calculations show that the reaction proceeds via a two-step process through a doublet spin surface. Finally, using biuret-modified Fe-TAML as the catalyst and NaOCl as the oxidant under catalytic conditions epoxide was formed with modest yields and turnover numbers. (Graph Presented).
- Singh, Kundan K.,Tiwari, Mrityunjay K.,Dhar, Basab B.,Vanka, Kumar,Sen Gupta, Sayam
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p. 6112 - 6121
(2015/07/15)
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- Chiral electron deficient ruthenium helical coordination polymer as a catalyst for the epoxidation of substituted styrenes
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An air and moisture stable ruthenium(III) formate complex [Ru(HCO2)Cl2]n has been synthesized and examined in the epoxidation of substituted styrenes. X-ray crystallographic data of this complex were determined and showed that the formate ligand coordinates to the ruthenium centers in a μ2-η2 fashion (syn, syn). Its asymmetric unit contains one Ru(III) ion together with the half of a formate ligand and one chloride anion, which are bridged between the metal centers, forming a 1-D chain coordination polymer. This electron deficient helical coordination polymer was employed in the epoxidation of para-fluorostyrene, affording the epoxide product in 92% yield. Natural chirality of this coordination polymer is applicable in asymmetric epoxidation reactions.
- Jahromi, Bahareh Tamaddoni,Kharat, Ali Nemati,Zamanian, Sara
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p. 137 - 140
(2015/01/30)
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- Catalytic and mechanistic studies into the epoxidation of styrenes using manganese complexes of structurally similar polyamine ligands
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Two structurally similar polyamine ligands (7 and 8) have been prepared, which differ only by the presence of either a secondary or tertiary nitrogen donor within their N5 donor set. The ligands, in combination with iron and manganese salts, have been screened for their efficacy as catalysts for the epoxidation of styrene, using both hydrogen peroxide and peracetic acid as oxidants. Clear differences in activity between the two systems were observed, with 7 proving most effective in the presence of MnSO4 with H 2O2, whereas ligand 8 proved to be effective with Mn(OTf)2, MnCl2 and Mn(ClO4)2 using peracetic acid as the oxidant. A Hammett analysis of the initial rate kinetics of the optimal systems, combined with analysis by UV-vis spectroscopy, indicates that the small structural differences in the ligands elicit profound changes in the nature of the active species formed. The Royal Society of Chemistry.
- Ilyashenko, Gennadiy,De Faveri, Giorgio,Follier, Thomas,Al-Safadi, Rawan,Motevalli, Majid,Watkinson, Michael
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p. 1124 - 1134
(2014/02/14)
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- Kinetics and mechanism of styrene epoxidation by chlorite: Role of chlorine dioxide
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An investigation of the kinetics and mechanism for epoxidation of styrene and para-substituted styrenes by chlorite at 25 °C in the pH range of 5-6 is described. The proposed mechanism in water and water/acetonitrile includes seven oxidation states of chlorine (-I, 0, I, II, III, IV, and V) to account for the observed kinetics and product distributions. The model provides an unusually detailed quantitative mechanism for the complex reactions that occur in mixtures of chlorine species and organic substrates, particularly when the strong oxidant chlorite is employed. Kinetic control of the reaction is achieved by the addition of chlorine dioxide to the reaction mixture, thereby eliminating a substantial induction period observed when chlorite is used alone. The epoxidation agent is identified as chlorine dioxide, which is continually formed by the reaction of chlorite with hypochlorous acid that results from ClO produced by the epoxidation reaction. The overall stoichiometry is the result of two competing chain reactions in which the reactive intermediate ClO reacts with either chlorine dioxide or chlorite ion to produce hypochlorous acid and chlorate or chloride, respectively. At high chlorite ion concentrations, HOCl is rapidly eliminated by reaction with chlorite, minimizing side reactions between HOCl and Cl2 with the starting material. Epoxide selectivity (>90% under optimal conditions) is accurately predicted by the kinetic model. The model rate constant for direct reaction of styrene with ClO2(aq) to produce epoxide is (1.16 ± 0.07) × 10-2 M -1 s-1 for 60:40 water/acetonitrile with 0.20 M acetate buffer. Rate constants for para substituted styrenes (R = -SO3 -, -OMe, -Me, -Cl, -H, and -NO2) with ClO2 were determined. The results support the radical addition/elimination mechanism originally proposed by Kolar and Lindgren to account for the formation of styrene oxide in the reaction of styrene with chlorine dioxide.
- Leigh, Jessica K.,Rajput, Jonathan,Richardson, David E.
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p. 6715 - 6727
(2014/07/22)
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- Asymmetric epoxidation of alkenes and benzylic hydroxylation with P450tol monooxygenase from Rhodococcus coprophilus TC-2
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P450tol monooxygenase was discovered as a unique and highly enantioselective enzyme for asymmetric epoxidation of some terminal alkenes containing electron-withdrawing groups and benzylic hydroxylation of several ethylbenzenes giving the corresponding useful and valuable products, such as (R)-2- and 3-substituted styrene oxides, (S)-4-substituted styrene oxides, and (S)-benzylic alcohols, in high ee.
- Li, Aitao,Wu, Shuke,Adams, Joseph P.,Snajdrova, Radka,Li, Zhi
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p. 8771 - 8774
(2014/07/22)
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- One-pot route to β-adrenergic blockers via enantioselective organocatalysed epoxidation of terminal alkenes as a key step
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A convenient and environmentally attractive one-pot two-step process for the synthesis of β-adrenergic blockers via Shi's organocatalytic epoxidation of terminal alkenes and subsequent aminolysis reaction of epoxides with isopropylamine under mild reaction conditions has been developed. This journal is the Partner Organisations 2014.
- Held, Felix E.,Wei, Shengwei,Eder, Kathrin,Tsogoeva, Svetlana B.
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p. 32796 - 32801
(2014/08/18)
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- FAK AND FLT3 INHIBITORS
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The use of a compound of the formula (I): (Formula (I)) in the preparation of a medicament for treating Acute Myeloid Leukemia or a disease ameliorated by the inhibition of Flt3, or Flt3 and FAK.
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Page/Page column 115
(2014/03/22)
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- Engineered P450pyr monooxygenase for asymmetric epoxidation of alkenes with unique and high enantioselectivity
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A triple mutant of P450pyr monooxygenase (P450pyrTM) catalysed the epoxidation of several para-substituted styrenes as the first enzyme showing high (R)-enantioselectivity and high conversion, demonstrated a broad substrate range, and showed high enantioselectivity for the epoxidation of an unconjugated 1,1-disubstituted alkene, 2-methyl-3-phenyl-1-propene, and a cyclic alkene, N-phenoxycarbonyl-1,2,5,6-tetrahydropyridine, respectively.
- Li, Aitao,Liu, Ji,Pham, Son Q.,Li, Zhi
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supporting information
p. 11572 - 11574
(2013/12/04)
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- Efficient and reusable Co/nitrogen doped hollow carbon sphere catalysts for the aerobic oxidation of styrene
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Monodispersed hollow carbon spheres (HCSs) were made by decomposition of gaseous CH3CN over silica St?ber spheres in a CVD reaction. The nitrogen doped HCSs (N = 8.7%) were used as support for well dispersed Co 3O4 nanoparticles (7-8 nm; 1% and 2% Co). The Co/N-HCS samples were calcined at various temperatures. The materials calcined at 300 C for 3 h were found to oxidize styrene to styrene oxide (styrene epoxidation) using dry air as oxidant (120 C/DMF) with 99% styrene conversion and 85% selectivity to styrene oxide; they could also be reused in repeat catalytic reactions.
- Nongwe, Isaac,Ravat, Vilas,Meijboom, Reinout,Coville, Neil J.
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- Synthesis, crystal structure and spectroscopic studies of a cobalt(III) Schiff base complex and its use as a heterogeneous catalyst for the oxidation reaction under mild condition
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A new Schiff base oriented Co(III) complex, (CoL)Cl4H2O (L = Schiff base), has been synthesized by careful design of the Schiff base ligand thorough oxidation of Co(II) to Co(III) during the reaction process. The complex has been characterized by single-crystal X-ray structure analysis and various spectral analyses. Structure analysis reveals that this monomeric complex crystallizes in triclinic P-1 space group. Supramolecular hydrogen bonding interactions among the guest water molecules and counter anion chloride leads to the formation of 1D water-chloride chain. A polymer anchored heterogeneous cobalt complex has been synthesized, characterized by various physicochemical techniques and successfully used for the oxidation of alkenes and sulfides using H2O2 as oxygen source. The influence of the various reaction parameters has been studied. The heterogeneous cobalt complex can be reused seven times without any significant loss in its catalytic activity.
- Islam, S. Manirul,Roy, Anupam Singha,Dalapati, Sasanka,Saha, Rajat,Mondal, Paramita,Ghosh, Kajari,Chatterjee, Saptarshi,Sarkar, Keka,Guchhait, Nikhil,Mitra, Partho
-
-
- 8-ETHYL-6-(ARYL)PYRIDO [2,3-D]PYRIMIDIN-7(8H) -ONES FOR THE TREATMENT OF NERVOUS SYSTEM DISORDERS AND CANCER
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Provided herein are PAK inhibitors and methods of utilizing PAK inhibitors for the treatment of CNS disorders such as neuropsychiatric disorders or neurofibromatosis. Also described herein are methods of utilizing PAK inhibitors for the treatment of cancer.
- -
-
Paragraph 00511
(2013/04/10)
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- Design, synthesis and biological evaluation of bivalent ligands against A 1-D 1 receptor heteromers
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Aim:To design and synthesize bivalent ligands for adenosine A 1-dopamine D 1 receptor heteromers (A 1-D 1 R), and evaluate their pharmacological activities.Methods:Bivalent ligands and their corresponding A 1 R monovalent ligands were designed and synthesized. The affinities of the bivalent ligands for A 1 R and D 1 R in rat brain membrane preparation were examined using radiolabeled binding assays. To demonstrate the formation of A 1-D 1 R, fluorescence resonance energy transfer (FRET) was conducted in HEK293 cells transfected with D 1-CFP and A 1-YFP. Molecular modeling was used to analyze the possible mode of protein-protein and protein-ligand interactions.Results:Two bivalent ligands for A 1 R and D 1 R (20a, 20b), as well as the corresponding A 1 R monovalent ligands (21a, 21b) were synthesized. In radiolabeled binding assays, the bivalent ligands showed affinities for A 1 R 10-100 times higher than those of the corresponding monovalent ligands. In FRET experiments, the bivalent ligands significantly increased the heterodimerization of A1R and D 1 R compared with the corresponding monovalent ligands. A heterodimer model with the interface of helixes 3, 4, 5 of A1R and helixes 1, 6, 7 from D 1 R was established with molecular modeling. The distance between the two ligand binding sites in the heterodimer model was approximately 48.4 ?, which was shorter than the length of the bivalent ligands.Conclusion:This study demonstrates the existence of A 1-D 1 R in situ and a simultaneous interaction of bivalent ligands with both the receptors.
- Shen, Jian,Zhang, Lei,Song, Wan-Ling,Meng, Tao,Wang, Xin,Chen, Lin,Feng, Lin-Yin,Xu, Ye-Chun,Shen, Jing-Kang
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p. 441 - 452
(2013/08/25)
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- METHOD FOR MANUFACTURING AN EPOXY COMPOUND AND METHOD FOR EPOXIDIZING A CARBON-CARBON DOUBLE BOND
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The present invention provides a method for producing an epoxy compound, comprising oxidizing a carbon-carbon double bond of an organic compound by hydrogen peroxide in the presence of a neutral inorganic salt and a mixed catalyst of a tungsten compound (a), at least one phosphorus compound selected from the group consisting of phosphoric acids, phosphonic acids, and salts thereof (b) and a surfactant (c), and an epoxidizing method comprising oxidizing a carbon-carbon double bond by hydrogen peroxide in the presence of the catalyst and the neutral inorganic salt.
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Page/Page column 14
(2012/05/07)
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- Olefin epoxidation with tert-butyl hydroperoxide catalyzed by functionalized polymer-supported copper(II) Schiff base complex
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A new polymer-supported Cu(II) Schiff base complex has been synthesized and characterized by elemental (including metal) analysis, FT-IR spectroscopy, UV-Vis diffuse reflectance spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The catalytic performance of this complex was evaluated in the epoxidation of styrene in acetonitrile/N,N-dimethylformamide (9:1) mixture with 70% tert-butyl hydroperoxide as an oxidizing agent under liquid phase reaction conditions for selective synthesis of styrene oxide. Suitable reaction conditions have been optimized by considering the effects of various reaction parameters such as temperature, reaction time, solvent, oxidant, catalyst amount, and styrene to hydroperoxide molar ratio for the maximum conversion of styrene as well as selectivity of styrene oxide. We have also investigated the epoxidation reaction of various olefins under the optimized reaction conditions. Comparison between catalytic activities of the polymer-supported Cu(II) Schiff base complex and its homogeneous analogue showed that the polymer-supported catalyst was more active. This heterogeneous complex was reused for five times. The selectivity of the heterogeneous catalyst does not change even after five times of reusing. Springer-Verlag 2011.
- Islam, Sk Manirul,Roy, Anupam Singha,Mondal, Paramita,Mobarok, Manir,Roy, Brindaban,Salam, Noor,Paul, Sumantra,Mondal, Sanchita
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experimental part
p. 815 - 823
(2012/10/07)
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- Stereoselective epoxidation of alkenes with hydrogen peroxide using a bipyrrolidine-based family of manganese complexes
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Novel manganese complexes containing N4-tetradentate ligands derived from chiral bipyrrolidinediamines catalyze the stereoselective epoxidation of a wide array of alkenes using low catalyst loadings (0.1 mol%) and hydrogen peroxide (1.2 equiv.) as terminal oxidant. This family of catalysts affords good to excellent yields (80-100%) and moderate to good ees (40-73%) in short reaction times (30 min) making efficient use of hydrogen peroxide.
- Garcia-Bosch, Isaac,Gomez, Laura,Polo, Alfonso,Ribas, Xavi,Costas, Miquel
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supporting information; experimental part
p. 65 - 70
(2012/03/27)
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- Synthesis, catalytic oxidation and oxidative bromination reaction of a reusable polymer anchored oxovanadium(IV) complex
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Polymer anchored oxovanadium catalyst was synthesized and characterized. The solid catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Its catalytic activity was evaluated for the oxidation of various alkenes, sulfides and aromatic alcohols with 30% H2O2 under mild reaction conditions. This catalyst was also effective for the oxidative bromination reaction of organic substrates with 80-100% selectivity of mono substituted products with H2O2/KBr at room temperature. The above reactions require minimum amount of H2O2, short time period and most importantly all the above reactions occur in aqueous medium. The developed catalyst can be facilely recovered and reused six times without significant decrease in activity and selectivity. This result confirms that the polymer anchored complex was not leached during the reaction, suggesting the true heterogeneous nature of the catalyst.
- Islam, Sk. Manirul,Roy, Anupam Singha,Mondal, Paramita,Salam, Noor
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experimental part
p. 38 - 48
(2012/05/21)
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- A recyclable polymer anchored copper(II) catalyst for oxidation reaction of olefins and alcohols with tert-butylhydroperoxide in aqueous medium
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A new reusable polymer anchored Cu(II) complex was synthesized which can acts as an efficient heterogeneous catalyst for oxidation of olefins and alcohols with tert-butylhydroperoxide (TBHP) in aqueous medium. The present catalyst well oxidized styrene and other olefins to their allylic products and alcohols were converted to their corresponding aldehydes in good-to-moderate yields. This catalyst can be easily recovered by filtration and recycled without significant loss of its catalytic performances.
- Islam,Roy, Anupam Singha,Mondal, Paramita,Paul, Sumantra,Salam, Noor
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p. 170 - 176
(2012/10/30)
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- FAK INHIBITORS
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A compound of the formula (I): where R1 or R2 is a cycle amine group and R5 is an aromatic group with a carbonyl containing substituent for use as a FAK inhibitor.
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Page/Page column 113
(2012/09/10)
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- An effective synthesis of acid-sensitive epoxides via oxidation of terpenes and styrenes using hydrogen peroxide under organic solvent-free conditions
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An efficient epoxidation process for various terpenes and styrenes using a hydrogen peroxide-tungsten catalytic system with organic solvent-and halide-free conditions was developed. In the presence of the catalytic system, Na 2WO4, PhP(O)(OH)2, and [Me(n-C 8H17)3N]HSO4, and under weak acidic conditions, hydrogen peroxide successfully epoxidized -pinene to -pinene oxide in 95% selectivity at 91% conversion, while the previously published conditions utilizing NH2CH2P(O)(OH)2 as a promoter provided no epoxide. Georg Thieme Verlag Stuttgart.
- Kon, Yoshihiro,Hachiya, Houjin,Ono, Yutaka,Matsumoto, Tomohiro,Sato, Kazuhiko
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experimental part
p. 1092 - 1098
(2011/05/14)
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- Oxidation of styrene and of some derivatives with H2O 2 catalyzed by novel imidazolium-containing manganese porphyrins: A mechanistic and thermodynamic interpretation
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The oxidation of styrene and derivatives with H2O2 catalyzed by manganese porphyrins in acetonitrile is described. The effect of the imidazolium substituent on the catalytic efficiency has been also considered. The thermodynamic analysis has indicated that enthalpy rules styrene oxidation when catalysts Mn(Porph)-1 and Mn(Porph)-2 are used whereas the entropy is the driven force for Mn(Porph)-3 and Mn(Porph)-4 catalyzed reactions. Interestingly, an enthalpy-entropy compensation phenomenon is observed when comparing the thermodynamic results obtained for catalysts Mn(Porph)-3 and Mn(Porph)-4. Hammett plots for the studied manganese porphyrins provided small ρ-values, and this is typical for multi-step reactions, indicating that there is no significant charge separation in the transition state. For Mn(Porph)-1 and Mn(Porph)-2 the formation of multiple active species can be put forward whereas for Mn(Porph)-3 and Mn(Porph)-4 a concerted-type mechanism, via metalloxetane intermediate, fits well with the values obtained for those catalysts. The imidazolium-based catalysts have shown to be efficient catalysts in styrene and derivatives oxidation with hydrogen peroxide.
- De Paula, Rodrigo,Sim?es, Mário M.Q.,Neves, M. Graa P.M.S.,Cavaleiro, José A.S.
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experimental part
p. 1 - 11
(2011/10/05)
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- Chiral epoxides via borane reduction of 2-haloketones catalyzed by spiroborate ester: Application to the synthesis of optically pure 1,2-hydroxy ethers and 1,2-azido alcohols
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An enantioselective borane-mediated reduction of a variety of 2-haloketones with 10% spiroaminoborate ester 1 as catalyst is described. By a simple basic workup of 2-halohydrins, optically active epoxides are obtained in high yield and with excellent enantiopurity (up to 99% ee). Ring-opening of oxiranes with phenoxides or sodium azide is investigated under different reaction conditions affording nonracemic 1,2-hydroxy ethers and 1,2-azido alcohols with excellent enantioselectivity (99% ee) and in good to high chemical yield. 2011 American Chemical Society.
- Huang, Kun,Wang, Haiyang,Stepanenko, Viatcheslav,De Jesus, Melvin,Torruellas, Carilyn,Correa, Wildeliz,Ortiz-Marciales, Margarita
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supporting information; experimental part
p. 1883 - 1886
(2011/06/20)
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- Asymmetric synthesis of β-adrenergic blockers through multistep one-pot transformations involving in situ chiral organocatalyst formation
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Two birds one stone: A new atom-economical one-pot approach to enantioselective chiral drug synthesis, involving in situ multistep organocatalyst formation and the application of the reaction for multistep sequential synthesis of β-adrenergic blockers is disclosed (see scheme).
- Wei, Shengwei,Messerer, Regina,Tsogoeva, Svetlana B.
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supporting information; scheme or table
p. 14380 - 14384
(2012/02/01)
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- Synthesis, catalytic oxidation and antimicrobial activity of copper(II) Schiff base complex
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A new polymer supported Cu(II) Schiff base complex was synthesized. The solid complex was characterized by Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Its homogeneous analogue was also prepared. The catalytic performances of the copper complex in oxidation reactions were evaluated for both homogeneous and heterogeneous systems. The copper(II) complex was found to be efficient catalyst for the oxidation of alkenes, alkanes and aromatic alcohols in the presence of hydrogen peroxide as oxidant at room temperature. The catalytic investigation revealed that the solid complex performs better than the homogeneous one as an oxidation catalyst. The solids containing the immobilized complex can be recovered from the reaction medium and reused almost five times, maintaining good catalytic activity. Furthermore, the in vitro toxicity of the ligand and complex was tested against the growth of bacterial species, viz., Staphylococcus aureus and Escherichia coli.
- Islam,Roy, Anupam Singha,Mondal, Paramita,Mubarak, Manir,Mondal, Sanchita,Hossain, Dildar,Banerjee, Satabdi,Santra
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experimental part
p. 106 - 114
(2011/05/12)
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- Synthesis, characterization, and catalytic activity of a polymer-supported copper(II) complex with a thiosemicarbazone ligand
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A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates including alkenes and alcohols using H 2O2 as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out.
- Islam, Manirul,Hossain, Dildar,Mondal, Paramita,Tuhina, Kazi,Roy, Anupam Singha,Mondal, Sanchita,Mobarak, Manir
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experimental part
p. 223 - 230
(2012/04/17)
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