- Proton-exchanged montmorillonite-mediated reactions of hetero-benzyl acetates: Application to the synthesis of Zafirlukast
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Proton-exchanged montmorillonite (H-mont) with outstanding surface characteristics can provide abundant acidic sites in the mesopores, and serve as an efficient heterogeneous catalyst for the synthesis of heterocycle-containing diarylmethanes via Friedel-Crafts-like alkylation of (hetero)arenes by heterobenzyl acetates under mild reaction conditions without requiring any additives or an inert atmosphere. Using this strategy, the gram-scale synthesis of indole-containing diarylmethane 13 has been accomplished in good yield for the preparation of Zafirlukast. In addition, H-mont can be applied to the nucleophilic substitution reactions of heterobenzyl acetate 5p with a variety of alcohols and 1,3-dicarbonyl compounds.
- Yang, Lei,Chen, Xuan,Ni, Kaidong,Li, Yuansheng,Wu, Jianhong,Chen, Weilin,Ji, Yin,Feng, Lili,Li, Fei,Chen, Dongyin
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supporting information
(2020/06/28)
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- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- Esterification of Tertiary Amides by Alcohols Through C?N Bond Cleavage over CeO2
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CeO2 has been found to promote ester forming alcoholysis reactions of tertiary amides. The present catalytic system is operationally simple, recyclable, and it does not require additives. The esterification process displays a wide substrate scope (>45 examples; up to 93 % isolated yield). Results of a density functional theory (DFT) study combined with in situ FT-IR observations indicate that the process proceeds through rate limiting addition of a CeO2 lattice oxygen to the carbonyl group of the adsorbed acetamide species with energy barrier of 17.0 kcal/mol. This value matches well with experimental value (17.9 kcal/mol) obtained from analysis of the Arrhenius plot. Further studies by in situ FT-IR and temperature programmed desorption using probe molecules demonstrate that both acidic and basic properties are important, and consequently, CeO2 showed the best performance for the C?N bond cleavage reaction.
- Toyao, Takashi,Nurnobi Rashed, Md.,Morita, Yoshitsugu,Kamachi, Takashi,Hakim Siddiki,Ali, Md. A.,Touchy,Kon, Kenichi,Maeno, Zen,Yoshizawa, Kazunari,Shimizu, Ken-ichi
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p. 449 - 456
(2018/09/11)
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- Synthesis of lipase nano-bio-conjugates as an efficient biocatalyst: Characterization and activity-stability studies with potential biocatalytic applications
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In the present study, we have synthesized lipase-nano-bio-conjugates via immobilization of various lipases on multiwall carbon nano-tubes (MCNT), in order to construct an efficient and recyclable biocatalytic system. In a screening study lipase Pseudomonas fluorescens (PFL) acted as an efficient biocatalyst (lipase-nano-bio-conjugates) which showed higher retention of lipase activity and protein loading. Consequently the immobilization support : lipase (MCNT : PFL) composition was screened in which MCNT : PFL (2 : 1) was calculated as a robust biocatalyst composition which showed higher activity retention and protein loading. This nano-bio-conjugate was then characterized in detail with physical and biochemical techniques using SEM, TEM, FTIR, Km, Vmax, catalytic efficiency and (%) water content analysis. This developed biocatalyst was further used for practical biocatalytic applications such as O-acylation reactions. Various reaction parameters were optimized in detail like reactant molar ratio (2 : 3.5), solvent, MCNT : PFL biocatalyst amount (36 mg), temperature (50°C) etc. The developed biocatalytic protocol was then extended to synthesize several (twenty-two) industrially important acylated moieties with an excellent yield, these products are well characterized by 1HNMR, 13CNMR and GCMS analysis. Moreover in the present study, we have reviewed the potential industrial applications of various synthesized compounds. Also, we have studied the thermodynamic aspect which demonstrated more feasibility of use of immobilized MCNT : PFL lipase over free lipase. Interestingly, immobilized MCNT : PFL lipase showed 2.3 fold higher catalytic activity than free PFL. Besides this, the biocatalyst was efficiently recycled for up to five cycles. Thus the present protocol demonstrated, (i) synthesis of nano-bio-conjugates as a bio-catalyst, (ii) detailed physical-biochemical characterization of nano-bio-conjugates, (iii) optimization of the biocatalytic protocol (iv) practical biocatalytic applications along with a mechanistic study (v) a thermodynamic feasibility study and (vi) recyclability study. 2015
- Badgujar, Kirtikumar Chandulal,Sasaki, Takehiko,Bhanage, Bhalchandra Mahadeo
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p. 55238 - 55251
(2015/07/07)
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- Synthesis, characterization and application of poly(N,N'-dibromo- Nethylnaphthyl-2,7-disulfonamide) as an efficient catalyst for the acetylation and deacetylation reactions
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In this work, a novel polymer namely poly(N,N'-dibromo-N-ethylnaphthyl-2,7- disulfonamide) (PBNS) is synthesized and characterized by studying its IR, 1H NMR, 13C NMR and thermal gravimetric analysis (TGA). This polymer is utilized as a highly efficient, heterogeneous and recyclable N-bromo reagent to catalyze acetylation of various compounds such as alcohols, phenols, thiol and amine with acetic anhydride under solvent-free conditions, and also it worthily catalyzes deacetylation of acetate esters in aqueous media.
- Khazaei, Ardeshir,Saednia, Shahnaz,Roshani, Liela,Kazem-Rostami, Masoud,Zare, Abdolkarim
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p. 159 - 167
(2014/05/20)
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- Smooth photocatalytic preparation of 2-substituted 1,3-benzodioxoles
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A mild and general method for the synthesis of potentially bioactive 2-substituted-1,3-benzodioxoles is presented. This is based on the photocatalyzed activation of methylene hydrogen atoms in the presence of tetrabutylammonium decatungstate (TBADT). The method gave yields ranging from 46-77% with no interference by benzene ring substituents, such as OR, COOMe, Me, or CHO. The OH group interfered, but protection regenerated the reactivity. 5-Chloro-1,3-benzodioxole was converted into a safrole derivative through a one-pot process involving two consecutive irradiations, at 366 nm for the photocatalyzed alkylation at position 2 and at 310 nm for the alkylation at position 5.
- Ravelli, Davide,Albini, Angelo,Fagnoni, Maurizio
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experimental part
p. 572 - 579
(2011/04/12)
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- Efficient acetylation of alcohols, phenols, and amines catalyzed by melamine trisulfonic acid (MTSA)
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Melamine trisulfonic acid (MTSA) was easily prepared by the reaction of melamine with neat chlorosulfonic acid at room temperature. This reagent can be used as an efficient catalyst for the acetylation of alcohols, phenols, and amines with Ac2O under mild and completely heterogeneous reaction conditions.
- Shirini, Farhad,Zolfigol, Mohammad Ali,Aliakbar, Ali-Reza,Albadi, Jalal
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experimental part
p. 1022 - 1028
(2010/05/18)
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- Separation, recovery and reuse of N-heterocyclic carbene catalysts in transesterification reactions
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A novel and convenient strategy to separate, recover and reuse N-heterocyclic carbene catalysts in transesterification reactions has been developed.
- Zeng, Tieqiang,Song, Gonghua,Li, Chao-Jun
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supporting information; experimental part
p. 6249 - 6251
(2010/02/16)
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- PROCESS FOR SYNTHESISING HELIOTROPINE AND ITS DERIVATIVES
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A new high-yield, easily industrialized process for synthesising compounds of formula (IV), in which X1 and X2, the same or different, are linear or branched C1-C8 alkyls, n and m are 0,1 or 2, with the proviso that n and m are not simultaneously 0; or (OX1)n and (OX2)m taken together form an O-T-O group where T is chosen from -CH2-, -CH2CH2-, -CH2CH2CH2-, -C(CH3)2-. The process comprises treating a chloromethyl derivative (I) with an alkaline acetate to form the intermediate acetylderivative (II); the intermediate (II) is to hydrolysed to form the alcohol (III); the alcohol (III) is then oxidised in the presence of air and catalysts to obtain the desired derivative (IV). The process runs its course within a short period of time, with high yields and high selectivity; in addition, the process does not require purification and separation of the intermediates and can therefore be favourably conducted in a single batch.
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Page/Page column 8
(2008/06/13)
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- Chemoselective acetylation of alcohols, amines, and thiols without catalyst and solvent
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Microwave induced rapid and selective acetylation of alcohols, amines and thiols with acetic anhydride was carried out under non-catalytic and solvent free conditions.
- Bandgar,Kasture,Kamble
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p. 2255 - 2259
(2007/10/03)
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- Desilylation-acetylation of trimethylsilyl ethers with acetic anhydride catalysed by montmorillonite K-10
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Two mild and simple one-step desilylation-acetylations of a variety of alkyl- and aryl-trimethylsilyl ethers, Me3SiOR(Ar), with acetic anhydride in the presence of montmorillonite K-10 clay are described.
- Movassagh,Lakouraj,Fasihi
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p. 348 - 349
(2007/10/03)
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- A facile one-step conversion of aromatic aldehydes to acetates
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Aromatic aldehydes are efficiently converted to the corresponding benzyl acetates with acetic anhydride and zinc in the presence of acidic aluminium oxide in dichloromethane at room temperature.
- Baruah
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- Acetylation and formylation of alcohols with triphenylphosphine and carbon tetrabromide in ethyl acetate or ethyl formate
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Alcohols were acetylated or formylated with triphenylphosphine and carbon tetrabromide in ethyl acetate or ethyl (or methyl) formate at room temperature. THP or TBDMS ether of primary alcohol got converted into formate or acetate under the experimental conditions employed in one pot operation.
- Hagiwara, Hisahiro,Morohashi, Kimie,Sakai, Hitoshi,Suzuki, Toshio,Ando, Masayoshi
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p. 5845 - 5852
(2007/10/03)
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