- Highly enantioselective copper-bisoxazoline-catalyzed allylic oxidation of cyclic olefins with tert-butyl p-nitroperbenzoate
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Catalytic asymmetric allylic oxidation of cyclic olefins ocurrs for the first time in very high (94-99% ee) enantioselectivity using copper(I) complexes of malonyl derived bisoxazolines and tert-butyl p-nitroperbenzoate giving allyl benzoates in moderate
- Andrus, Merritt B.,Zhou, Ziniu
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- Chiral bisoxazoline ligands with a biphenyl backbone: Development and application in catalytic asymmetric allylic oxidation of cycloolefins
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A simple and efficient method for the synthesis of chiral biphenylbisoxazoline ligands was developed. The bishydroxylamide precursors of ligands showed a dynamic atropselective resolution effect in the crystallization process. When biphenylbisoxazoline ligands were coordinated to tetrakis(acetonitrile)copper(I) hexafluorophosphate, it resulted in the formation of only a single diastereomer complex (S,aS,S), which behaved as a catalyst for the enantioselective allylic oxidation of cycloolefins. The enantioselectivity, yield, and rate of this reaction were optimized under different conditions, such as a change of solvents, temperature, and additives and also using various copper salts. The use of SBA-15 mesoporous silica as an additive played a crucial role in increasing the efficiency of the reaction.
- Samadi, Saadi,Jadidi, Khosrow,Notash, Behrouz
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- Immobilization of (l)-valine and (l)-valinol on SBA-15 nanoporous silica and their application as chiral heterogeneous ligands in the Cu-catalyzed asymmetric allylic oxidation of alkenes
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SBA-15 nanoporous silica was synthesized by hydrothermal method using P123 surfactant and tetraethoxyortosilicate in acidic condition and then functionalized by 3-chloropropyltrimethoxysilane. Next, by immobilization of chiral amino acid (S)-2-amino-3-methyl butanoic acid (l-valine) and chiral amino alcohol (S)-2-amino-3-methylbutane-1-ol (l-valinol), preparedviathe reduction ofl-valine by NaBH4/I2in THF, on functionalized-SBA-15, chiral heterogeneous ligands AL*-i-Pr-SBA-15 and AA*-i-Pr-SBA-15 were prepared and characterized by FT-IR, XRD, TGA, EDX, SEM, BET-BJH techniques. The asymmetric allylic oxidation of alkenes was done using copper-complexes of these ligands and the as-synthesized peresters. The reactions were optimized by varying various parameters such as temperature, solvent, amount of chiral heterogeneous ligand, as well as the type and amount of copper salt. Under optimized conditions, 6 mg of AL*-i-Pr-SBA-15 and 3.2 mol% of Cu(CH3CN)4PF6in acetonitrile at 50 °C, the chiral allylic ester was obtained with 80% yield and 39% enantiomeric excess in 24 h. The recyclability of the chiral heterogeneous catalysts was also evaluated without significant reduction in the reaction results up to three runs.
- Ashouri, Akram,Mahramasrar, Mahsa,Majidian, Shiva,Rashid, Hersh I,Samadi, Saadi
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p. 17630 - 17641
(2021/10/04)
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- Sunlight assisted solvent free synthesis of tert-butylperesters
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A green and efficient methodology has been developed for the direct conversion of aryl aldehydes to the corresponding tert-butyl peresters. The reaction has been carried out in absence of any solvent and the sunlight is used as the green source of energy. In this reaction tetrabutylammonium iodide (TBAI) acts as the mild organo catalyst and tert-butyl hydroperoxide (TBHP) serve as the source of tert-butyl group.
- Shit, Prasenjit,Singha, Raju
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supporting information
p. 1 - 6
(2020/07/15)
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- A Woven Supramolecular Metal-Organic Framework Comprising a Ruthenium Bis(terpyridine) Complex and Cucurbit[8]uril: Enhanced Catalytic Activity toward Alcohol Oxidation
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The self-assembly of a diamondoid woven supramolecular metal–organic framework wSMOF-1 has been achieved from intertwined [Ru(tpy)2]2+ (tpy=2,2′,6′,2′′-terpyridine) complex M1 and cucurbit[8]uril (CB[8]) in water, where the intermolecular dimers formed by the appended aromatic arms of M1 are encapsulated in CB[8]. wSMOF-1 exhibits ordered pore periodicity in both water and the solid state, as confirmed by a combination of 1H NMR spectroscopy, UV-vis absorption, isothermal titration calorimetry, dynamic light scattering, small angle X-ray scattering and selected area electron diffraction experiments. The woven framework has a pore aperture of 2.1 nm, which allows for the free access of both secondary and primary alcohols and tert-butyl hydroperoxide (TBHP). Compared with the control molecule [Ru(tpy)2]Cl2, the [Ru(tpy)2]2+ unit of wSMOF-1 exhibits a remarkably higher heterogeneous catalysis activity for the oxidation of alcohols by TBHP in n-hexane. For the oxidation of 1-phenylethan-1-ol, the yield of acetophenone was increased from 10 percent to 95 percent.
- Li, Zhan-Ting,Liu, Yi,Wang, Hui,Wang, Ze-Kun,Xu, Zi-Yue,Zhang, Dan-Wei,Zhang, Yun-Chang
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p. 1498 - 1503
(2020/08/05)
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- 2-Aminopyrazine-functionalized MCM-41 nanoporous silica as a new efficient heterogeneous ligand for Cu-catalyzed allylic C–H bonds oxidation of olefins
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In spite of the importance of the application of allylic C–H bond oxidation of olefins in organic synthesis and existence of the numerous reports, lots of limitations such as large excess of the olefin respect to the oxidant, low chemical yield, long time of reaction and a large amount of the catalyst were reminded. We introduced a novel catalytic system using functionalized MCM-41 as catalyst support to promote efficiency of this reaction. The heterogeneous ligand Pyr-MCM-41 was prepared by substituted 2-aminopyrazine ligand on functionalized MCM-41 with 3-chloropropyltrimthoxysilane and characterized by FT-IR, XRD, SEM, EDX, BET, TGA, CHN techniques. In situ immobilized Pyr-MCM-41 by copper (I) trifluoromethanesulfonate (CuOTf) was applied in direct catalytic esterification of inert C–H bonds in olefins using various peresters at room temperature.
- Samadi, Saadi,Ashouri, Akram,Kamangar, Shadi,Pourakbari, Fatemeh
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p. 557 - 569
(2019/11/03)
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- Designing chiral amido-oxazolines as new chelating ligands devoted to direct Cu-catalyzed oxidation of allylic C–H bonds in cyclic olefins
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A new type of amido-oxazoline ligands was conveniently synthesized from inexpensive and commercially available materials in high yields and enantiomeric excesses. The corresponding chiral copper complexes with this class of ligands [C2 symmetric S,S-bis(amido-oxazoline-Cu(II) complex] were synthesized accordingly. The ORTEP diagram of ligand 6a and complex 6a-copper were compared and characterization of the complex confirmed the involvement of both dentate parts of the ligands, the oxygen and nitrogen atoms, in complexation with copper. The utilization of this amido-oxazoline ligands in the copper-catalyzed enantioselective esterification of allylic C–H bonds of cyclic olefins with tert-butyl-4-nitrobenzoperoxoate resulted in the highest activities, yields (up to 95%) and enantioselectivities (up to 96%) in the presence of HZSM-5 zeolite. These new findings highlight the protocol as one of the most attractive and useful methods for the oxidation of the asymmetric allylic C–H bond of cycloalkenes compared to other methodologies reported in the literature.
- Samadi, Saadi,Jadidi, Khosrow,Samadi, Mojgan,Ashouri, Akram,Notash, Behrouz
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p. 862 - 867
(2019/01/08)
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- A significant improvement in enantioselectivity, yield, and reactivity for the copper-bi-o-tolyl bisoxazoline-catalyzed asymmetric allylic oxidation of cyclic olefins using recoverable SBA-15 mesoporous silica material
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A series of chiral bi-o-tolyl bisoxazoline ligands 1 and 2 were conveniently synthesized on a gram scale from inexpensive and commercially available 3-methyl benzoic acid in eight steps. The catalytic and induced asymmetric effects of the chiral copper (I) complexes of these ligands on the asymmetric allylic oxidation of cycloolefins were investigated in the presence of various nano-sized additives. When SBA-15 mesoporous silica was used in conjunction with these ligands very highly enantioselectivities (up to 97% ee) and excellent yields (up to 99%) of the corresponding chiral allylic esters were obtained in a reasonably short period of time.
- Samadi, Saadi,Nazari, Saber,Arvinnezhad, Hamid,Jadidi, Khosrow,Notash, Behrouz
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p. 6679 - 6686
(2013/07/26)
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- Studies on enantioselective allylic oxidation of olefins using peresters catalyzed by Cu(I)-complexes of chiral pybox ligands
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Enantioselective allylic oxidation of olefins with various peresters, using a catalytic amount of Cu(i)-pybox complex, can be tuned to achieve high asymmetric induction (up to 98% ee) by choosing a unique combination of a ligand and a perester at room temperature. The asymmetric induction in the reaction strongly depends on the nature of the substituents attached to the aryl ring of peresters. The presence of a gem-diphenyl group at C-5 and secondary or tertiary alkyl substituents at the chiral center (C-4) of the oxazoline rings is crucial for high enantioselectivity. A π-π stacking model has been proposed and discussed to explain the stereochemical outcome of the reaction. The Royal Society of Chemistry 2006.
- Ginotra, Sandeep K.,Singh, Vinod K.
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p. 4370 - 4374
(2008/09/19)
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- Selective oxidation of aromatic aldehydes to arenecarboxylic acids using ebselen-tert-butyl hydroperoxide catalytic system
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It has been found that aromatic aldehydes with electron-withdrawing as well as electron-donating substituents are oxidized to arenecarboxylic acids using tert-butyl hydroperoxide in the presence of ebselen (2-phenylbenzisoselenazol-3(2H)-one) as a catalyst. The reaction is highly chemoselective and formation of phenols, being the products of competitive Baeyer-Villiger rearrangement, is marginal. It has been assumed that this rearrangement is inhibited by steric hindrance of the electron-deficient oxygen atom in the transient tetrahedral intermediate.
- Wójtowicz, Halina,Brza?szcz, Monika,Kloc, Krystian,M?ochowski, Jacek
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p. 9743 - 9748
(2007/10/03)
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- Asymmetric allylic oxidation with biarylbisoxazoline-copper(I) catalysis
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Eight new bi-o-tolyl bisoxazolines were made and used as ligands in the copper catalyzed asymmetric allylic oxidation reaction. Three benzoyl tert-butyl peresters, p-nitro, o-iodo, and 2,4,6-trichloro were made and used with cyclohexene and cyclopentene w
- Andrus, Merritt B,Asgari, Davoud
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p. 5775 - 5780
(2007/10/03)
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- Catalytic enantioselective allylic oxidation of olefins with copper(I) catalysts and new perester oxidants
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Asymmetric allylic oxidation of cyclic olefins using a catalytic amount of copper(I) bisoxazoline complexes and new peresters was investigated to give allylic benzoate esters in high selectivity (~80%ee), yield (70-80%), and at reasonable rates (5-7 d) at
- Andrus, Merritt B.,Chen, Xi
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p. 16229 - 16240
(2007/10/03)
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- Enantioselective allylic oxidation of cycloalkenes by using Cu(II)-tris(oxazoline) complex as a catalyst
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Optically active copper(II)-tris(oxazoline) complex that was synthesized as a model compound of the active site of non-heme oxygenase, was found to catalyze allylic oxidation of cycloalkenes to give the corresponding 2-cycloalkenyl benzoates with moderate to excellent enantioselectivity (up to 93% ee) under die Kharash-Sosnovsky reaction conditions.
- Kawasaki, Ken-Ichi,Katsuki, Tsutomu
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p. 6337 - 6350
(2007/10/03)
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- New Methods and Reagents in Organic Synthesis. 43. A New Synthesis of tert-Butyl Peroxycarboxylates Using Diethyl Phosphorocyanidate (DEPC)
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Condensation of carboxylic acids with tert-butyl hydroperoxide has been smoothly achieved by the use of diethyl phosphorocyanidate and triethylamine under mild reaction conditions, giving tert-butyl peroxycarboxylates in good yields.Keywords - tert-butyl
- Hamada, Yasumasa,Mizuno, Akira,Ohno, Tomoyasu,Shioiri, Takayuki
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p. 3683 - 3685
(2007/10/02)
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- REACTION OF NUCLEOPHILES WITH ELECTRON ACCEPTORS BY SN2 OR ELECTRON TRANSFER (ET) MECHANISMS: TERT-BUTYL PEROXYBENZOATE/DIMETHYL SULFIDE AND BENZOYL PEROXIDE/N,N-DIMETHYLANILINE SYSTEMS.
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This study is one of a series that probes the reactions of nucleophiles with peroxides, reactions that can occur either by an initial S//N2 reaction or by an electron-transfer (ET) reaction. The products and kinetics are reported for the reaction of dimethyl sulfide and a series of ring-substituted aryl methyl sulfides with tert-butyl peroxybenzoate (TBP) and four ring-substituted TPB's. Kinetic analysis allows the separation of the rate constants for unimolecular homolysis (k//1) and those for the decomposition of the TBP by the sulfide (k//2). The bimolecular reaction is accelerated by electron-withdrawing substituents in the TBP; for example, when 3,5-(NO//2)//2-TBP is used, k//2/k//1 is 12,000. The products that are formed are consistent with a radical process; however, this evidence is not regarded as conclusive.
- Pryor,Hendrickson Jr.
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p. 7114 - 7122
(2007/10/02)
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