- Efficient continuous kinetic resolution of racemic 2-aminobutanol over immobilized penicillin G acylase
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In this paper, an efficient method was established for continuous kinetic resolution of racemic 2-aminobutanol by selective hydrolysis of N-phenylacetyl (±)-2-aminobutanol over immobilized penicillin G acylase (PGA) in a fixed-bed reactor. Several N-acylated derivatives of 2-aminobutanol were screened in batch experiments, and it was found that the hydrolysis of N-phenylacetyl (±)-2-aminobutanol proceeded smoothly in the presence of immobilized penicillin G acylase with satisfied enantioselectivity. Thus, the reaction parameters were optimized in a fixed-bed reactor. Under the optimized conditions, 39.3% conversion of N-phenylacetyl (±)-2-aminobutanol and 98.2% ee value of S-2-aminobutanol were obtained. This fixed-bed system was operated continuously for 40?h without significant decrease of enzyme activity. It has been demonstrated to be more efficient compared to the batch experiments.
- Wang, Jianxin,Liu, Na,Cheng, Xiaobo,Chen, Ligong
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- Catalytic Alkene Difunctionalization via Imidate Radicals
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The first catalytic strategy to harness imidate radicals has been developed. This approach enables alkene difunctionalization of allyl alcohols by photocatalytic reduction of their oxime imidates. The ensuing imidate radicals undergo consecutive intra- and intermolecular reactions to afford (i) hydroamination, (ii) aminoalkylation, or (iii) aminoarylation, via three distinct radical mechanisms. The broad scope and utility of this catalytic method for imidate radical reactivity is presented, along with comparisons to other N-centered radicals and complementary, closed-shell imidate pathways.
- Nakafuku, Kohki M.,Fosu, Stacy C.,Nagib, David A.
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p. 11202 - 11205
(2018/09/12)
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- Copper-amino group complexes supported on silica-coated magnetite nanoparticles: Efficient catalyst for oxidative amidation of methyl arenes
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Magnetite nanoparticles coated with mesoporous silica, Fe3O4@SiO2, were prepared. Surface functionalization of this core-shell nanocomposite with (3-aminopropyl)trimethoxysilane (APTMS) followed by its reaction with Cu(OAc)2 was used to develop a new heterogeneous copper complex (Fe3O4@SiO2-APTMS-Cu). The structure and composition of the synthesized nanocatalyst were characterized by FTIR, SEM, VSM, TEM, XRD, and ICP analyses. The catalytic activity of the synthesized catalyst was probed in the oxidative amidation reaction of methyl arenes with amine hydrochloride salts. Various primary, secondary, and tertiary amides were prepared by this method. The magnetic properties of this catalyst lead to easy separation as well as providing significant catalyst recyclability. The catalyst is reusable 6 times without significant decrease in its catalytic activity.
- Karimi, Meghdad,Ghandi, Leila,Saberi, Dariush,Heydari, Akbar
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supporting information
p. 3900 - 3908
(2018/03/06)
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- A Heterogeneous Niobium(V) Oxide Catalyst for the Direct Amidation of Esters
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This study reports the first example of a heterogeneous catalytic system for the direct amidation of various esters with amines. Of 25 types of catalyst, Nb2O5 shows the highest activity in the amidation of methyl benzoate with aniline. Nb2O5 gives high yields in the amidation of various esters and amines under solvent-free conditions, is reusable, and shows higher turnover numbers than previously reported homogeneous catalysts such as La(OTf)3. IR spectroscopic studies of ethyl acetate adsorbed on the catalysts show a strong acid-base interaction between the Nb5+ Lewis acid site and carbonyl oxygen, which can result in high reactivity of the ester with a nucleophile (amine) and, thus, high activity of Nb2O5. Kinetic results show that the activity of Nb2O5 does not markedly decrease with increasing aniline concentration, in contrast to reference catalysts TiO2 and La(OTf)3. The relatively low negative impact of basic molecules on the Lewis acid catalysis of Nb2O5 also enables its high activity.
- Ali, Md. Ayub,Siddiki, S. M. A. Hakim,Kon, Kenichi,Shimizu, Ken-Ichi
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p. 2705 - 2710
(2015/09/15)
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- Green synthesis of benzamides in solvent- and activation-free conditions
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Herein, we describe a clean and ecocompatible pathway for both N-benzoylation and N-acetylation of anilines, amines, diamines, and aminoalcohols using three enol esters with good yields. We have improved the use of vinyl benzoate for the direct introduction of a benzamido-moiety under solvent- and activation-free conditions. The recovered amides are easily isolated by crystallization. Copyright
- Alalla, Affef,Merabet-Khelassi, Mounia,Aribi-Zouioueche, Louisa,Riant, Olivier
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supporting information
p. 2364 - 2376
(2014/07/22)
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- Transition-metal-free oxidative amidation of benzyl alcohols with amines catalyzed by NaI: A new method for the synthesis of benzamides Dedicated to the memory of Professor Ahmad Sodagar
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A simple, inexpensive, and efficient method for the synthesis of benzamides via the reaction of benzyl alcohols and amine hydrochloride salts in the presence of NaI as a green catalyst is described. Various derivatives of benzamide were synthesized in moderate to good yields using this method.
- Karimi, Meghdad,Saberi, Dariush,Azizi, Kobra,Arefi, Marzban,Heydari, Akbar
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p. 5351 - 5353
(2015/02/18)
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- Process for manufacturing 2-aminobutanol
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The invention relates to a method of preparation of 2-aminobutanol from readily available raw materials. The method of this invention is based on the reaction between 1.2-epoxybutane or isomeric butylene halogenehydrines with ammonia. The product, isomeric aminobutanols, are, subsequently transformed into 2-ethylaziridine by means of esterification with sulphuric acid followed by treatment with alkali. 2-Ethylaziridine is then submitted to a reaction with aromatic carboxylic acid or with aromatic orthobicarboxylic acid anhydride which produces the corresponding monomeric or polymeric amide, which is transformed into 2-aminobutanol by hydrolysis. The method of this invention is a multistage one but is quite simple and employs aqueous solutions and organic solvents, such as chloroform or benzene, which may be easily recovered.
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