- Electronic Effect-Guided Rational Design of Candida antarctica Lipase B for Kinetic Resolution Towards Diarylmethanols
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Herein, we developed an electronic effect-guided rational design strategy to enhance the enantioselectivity of Candida antarctica lipase B (CALB) mutants towards bulky pyridyl(phenyl)methanols. Compared to W104A mutant previously reported with reversed S-stereoselectivity toward sec-alcohols, three mutants (W104C, W104S and W104T) displayed significant improvement of S-enantioselectivity in the kinetic resolution (KR) of various phenyl pyridyl methyl acetates due to the increased electronic effects between pyridyl and polar residues. The electronic effects were also observed when mutating other residues surrounding the stereospecificity pocket of CALB, such as T42A, S47A, A281S or A281C, and can be used to manipulate the stereoselectivity. A series of bulky pyridyl(phenyl) methanols, including S-(4-chlorophenyl)(pyridin-2-yl) methanol (S-CPMA), the intermediate of bepotastine, were obtained in good yields and ee values. (Figure presented.).
- Li, Dan-Yang,Lou, Yu-Jiao,Xu, Jian,Chen, Xiao-Yang,Lin, Xian-Fu,Wu, Qi
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supporting information
p. 1867 - 1872
(2021/02/12)
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- Metal-Free Aerobic Oxidative C–O Coupling of C(sp3)–H with Carboxylic Acids Catalyzed by DDQ and tert-Butyl Nitrite
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The formation of the C–O bond is one of the hot topics in the area of C(sp3)–H bond functionalization. A metal-free oxidative cross-coupling between benzylic C(sp3)–H bond and carboxylic acids has been developed. The reactions were performed with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as the catalyst, tert-butyl nitrite (TBN) as the co-catalyst, and molecular oxygen as the terminal oxidant. A variety of diarylmethanes could be successfully coupled with various carboxylic acids to obtain diarylmethanol esters in good to excellent yields. In addition, 2-benzylbenzoic acids could be converted into phthalides in moderate yields through an intramolecular oxidative cyclization.
- Pan, Decheng,Pan, Zilong,Hu, Zhiming,Li, Meichao,Hu, Xinquan,Jin, Liqun,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu
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p. 5650 - 5655
(2019/08/20)
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- Synthesis and characterization of ionic liquid immobilized on magnetic nanoparticles: A recyclable heterogeneous organocatalyst for the acetylation of alcohols
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Herein, we describe a simple and efficient procedure for the preparation of 3-((3-(trisilyloxy)propyl)propionamide)-1-methylimidazolium chloride ionic liquid supported on magnetic nanoparticle (TPPA-IL-Fe3O4). The structure of this magnetic ionic liquid is fully characterized by FT-IR, TGA, XRD, VSM, SEM, EDX and DLS techniques. TPPA-IL-Fe3O4 is employed as a catalyst for the acetylation of alcohols with acetic anhydride under mild and heterogeneous conditions at room temperature with good to excellent yields. The magnetic catalyst could be readily separate from the reaction media by simple magnetic decantation, and reused several times without significant loss of its catalytic activity.
- Ghorbani-Choghamarani, Arash,Norouzi, Masoomeh
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p. 832 - 840
(2015/11/16)
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- L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate (supported on silica gel) as a new and efficient catalyst for acylation of alcohols, phenols and amines under solvent-free conditions
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In the present work, L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate, supported on silica gel was prepared and characterized by Mass spectroscopy, 1H NMR, 13CNMR, FT IR and elemental analysis (CHN) methods. This heterogenized catalyst can be used as an efficient catalyst for the acylation of alcohols, phenols, and amines with acetic anhydride under mild and solvent-free conditions. Simple work-up, stability of the catalyst, nontoxicity and good to high yields are the advantages of this work.
- Hajjami, Maryam,Ghorbani-Choghamarani, Arash,Khani, Zahra
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p. 324 - 329
(2013/07/26)
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- A novel lipase enzyme panel exhibiting superior activity and selectivity over lipase B from Candida antarctica for the kinetic resolution of secondary alcohols
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A novel, commercially available lipase enzyme panel performing kinetic bioresolutions of a number of secondary alcohols is reported. The secondary alcohols that have been chosen are known from the literature to be particularly challenging substrates to resolve. Following initial screening, four co-solvents were investigated for each lead enzyme in an effort to assess their tolerance to common organic solvents. The superiority of these novel enzymes over lipase B from Candida antarctica (CALB) has been demonstrated.
- O'Neill, Maeve,Beecher, Denis,Mangan, David,Rowan, Andrew S.,Monte, Agnieszka,Sroka, Stefan,Modregger, Jan,Hundle, Bhupinder,Moody, Thomas S.
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experimental part
p. 583 - 586
(2012/08/13)
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- DDQ-catalyzed oxidative C-O coupling of sp3 C-H bonds with carboxylic acids
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Da-ddy, DDQ: By using catalytic amounts of DDQ combined with MnO 2 as oxidant, an efficient oxidative C-O coupling of benzylic sp 3 C-H bonds with carboxylic acids affords a series of carboxylic esters in 70-98 % yields. A wide range
- Yi, Hong,Liu, Qiang,Liu, Jie,Zeng, Ziqi,Yang, Yuhong,Lei, Aiwen
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p. 2143 - 2146
(2013/01/15)
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- Spinel-type zinc aluminate (ZnAl2O4) nanoparticles prepared by the co-precipitation method: A novel, green and recyclable heterogeneous catalyst for the acetylation of amines, alcohols and phenols under solvent-free conditions
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Zinc aluminate (ZnAl2O4) nanoparticles with an average particle size of about 8 nm were easily prepared by the co-precipitation method using aqueous ammonia solution as the precipitating agent. This nanosized spinel-type oxide was characterized by TGA, XRD, FT-IR, TEM, and surface area measurement and used as the heterogeneous catalyst for the acetylation reaction. Efficient acetylation of various amines, alcohols and phenols was carried out over ZnAl2O4 nanoparticles using acetic anhydride and/or acetyl chloride as the acetylating agents at room temperature without the use of a solvent. The method is highly selective, allowing the alcoholic hydroxyl group to be protected while the phenolic hydroxyl group remains intact, and the amine group can be acetylated in the presence of the hydroxyl group. This method is fast and has a high yield. It is also clean, safe, cost effective, compatible with substrates that have other functional groups and very suitable for practical organic synthesis. In addition, the catalyst can be reused without significant loss of activity. Indeed, the catalytic activity of the ZnAl2O4 nanoparticles is higher than that of bulk ZnAl2O4.
- Farhadi, Saeid,Panahandehjoo, Somayeh
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scheme or table
p. 293 - 302
(2010/09/04)
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- Copper-catalyzed substitution reactions of acylal with organomanganese reagents
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A mild method for the copper-catalyzed substitution of aldehyde acylals with organomanganese reagents is reported. This operationally simple C-C bond-forming protocol uses different Cu(I) catalysts. Acylal from trans-cinnamaldehyde furnishes conjugated addition product when reacted with alkyl and aryl organomanganese reagents in presence of 10 mol % of Cu(NCMe) 2 (PPh3)2[BF4] and 2 equivalent of Me3Si-C1 as an accelerator. This reagent can be efficiently used in the substitution of one acetate group of aromatic acylal to form esters in high yield.
- Deshmukh, Madhukar B.,Jadhav, Sunil D.,Kadam, Shashikant V.
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p. 989 - 994
(2008/09/18)
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- Trans-esterification in dry media using ferric perchlorate adsorbed on silica gel
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Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic grade silica gel in the presence of ethyl acetate (to be used for trans-esterification) produces a supported reagent, Fe(ClO4)3(EtOAc)6/SiO2. This reagent, has been found effective for the rapid and high yield of esters via trans- esterification on grinding in the presence of alcohols/carboxylic acids using pestle and mortar in the solid state.
- Parmar, Anupama,Goyal, Rita,Kumar, Baldev,Kumar, Harish
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p. 139 - 143
(2007/10/03)
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- The chemistry of acylals. Part I. The reactivity of acylals towards Grignard and organolithium reagents
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Aldehyde acylals have been prepared and reacted with Grignard and alkyllithium reagents. Acylals from formaldehyde furnished complex reaction mixtures when reacted with both reagents. Acylals of other aldehydes gave reaction mixtures that consisted mainly of an ester, generated by replacing one of the carboxy groups with the organic part of the organometallic reagent, and regenerated aldehyde. The esters were formed in the highest yields. Yields above 90% were experienced when the acylals were reacted with Grignard reagents under Barbier conditions.
- Sydnes, Leiv K.,Sandberg, Marcel
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p. 12679 - 12690
(2007/10/03)
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- Iron (III) perchlorate: A reagent for trans-esterification
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Iron (III) perchlorate has successfully been used for the trans-esterification of ethyl acetate with alcohols and acids.
- Kumar, Baldev,Kumar, Harish,Parmar, Anupama
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p. 292 - 293
(2007/10/02)
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