- Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O-Acetals
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For over half a century, transition-metal-catalyzed homogeneous hydrogenation has been mainly focused on neutral and readily prepared unsaturated substrates. Although the addition of molecular hydrogen to C=C, C=N, and C=O bonds represents a well-studied paradigm, the asymmetric hydrogenation of cationic species remains an underdeveloped area. In this study, we were seeking a breakthrough in asymmetric hydrogenation, with cationic intermediates as targets, and thereby anticipating applying this powerful tool to the construction of challenging chiral molecules. Under acidic conditions, both N- or O-acetylsalicylamides underwent cyclization to generate cationic intermediates, which were subsequently reduced by an iridium or rhodium hydride complex. The resulting N,O-acetals were synthesized with remarkably high enantioselectivity. This catalytic strategy exhibited high efficiency (turnover number of up to 4400) and high chemoselectivity. Mechanistic studies supported the hypothesis that a cationic intermediate was formed in situ and hydrogenated afterwards. A catalytic cycle has been proposed with hydride transfer from the iridium complex to the cationic sp2 carbon atom being the rate-determining step. A steric map of the catalyst has been created to illustrate the chiral environment, and a quantitative structure–selectivity relationship analysis showed how enantiomeric induction was achieved in this chemical transformation.
- Sun, Yongjie,Zhao, Qingyang,Wang, Heng,Yang, Tilong,Wen, Jialin,Zhang, Xumu
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supporting information
p. 11470 - 11477
(2020/08/10)
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- 1. 3 - Benzoxazine - 2, 4 (3 H) - dione derivatives and their synthesis and use (by machine translation)
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The invention relates to a acetylcholine esterase with phosphodiesterase V enzyme inhibition benzoxazine dione derivative and its synthetic method and use, and in particular relates to the structure of the general formula (I) of 1, 3 benzoxazine - 2, 4 (3 H) - dione derivatives, R1 , R2 , R3 , R4 , R5 , R6 , R7 , R8 And R9 The specification of the existing limited to. This invention refers to these compound structure and synthetic method and in vitro acetylcholine esterase with phosphodiesterase V inhibiting activity, can be further developed into new drugs for treating Alzheimer's disease. (by machine translation)
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Paragraph 0050; 0052; 0053
(2018/10/19)
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- Novel design of recyclable copper(II) complex supported on magnetic nanoparticles as active catalyst for Beckmann rearrangement in poly(ethylene glycol)
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Copper complex-functionalized magnetic core–shell nanoparticles (Fe3O4@SiO2-Lig-Cu) were prepared and characterized using various techniques. The activity of the new catalyst was tested for the Beckmann rearrangement. The reaction conditions allow for the conversion of a wide variety of aldoximes, including aromatic and heterocyclic ones, to amides in good to excellent yields. High efficiency, mild reaction conditions, easy work-up, use of poly(ethylene glycol) as a green medium and simple purification of products are important advantages of this system. Moreover, the eco-friendly heterogeneous nanocatalyst could be easily recovered from the reaction mixture using an external magnet and reused several times.
- Keyhaniyan, Mahdi,Shiri, Ali,Eshghi, Hossein,Khojastehnezhad, Amir
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- Deuterium-Substituted Oxazepin Compounds
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Described are deuterium-substituted oxazepin compounds of structural Formula I, which are inhibitors/blockers of the late sodium current. Also described are pharmaceutical compositions comprising the deuterium-substituted oxazepin compounds, and methods of use thereof.
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Paragraph 0360; 0361
(2018/03/24)
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- Acid Catalyzed Direct-Amidation-Dehydrocyclization of 2-Hydroxy-acetophenones to Benzoxazoles by a One-Pot Sustainable Synthesis
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A series of 2-methyl-benzoxazoles have been synthesized starting from 2-hydroxy-acetophenones via a one-pot three steps reaction. Hydroxylamonium salt has been used as amidation agent. The reaction occurs with different anions, but the best results is achieved with hydroxylamonium hydrchloride. Despite the number of consecutive stages, the reaction is highly selective. Mild reaction conditions and various solvents can be used, but trifluoroacetic acid is the preferred. Almost, complete recovery of the trifluoroacetic acid can be achieved by vacuum distillation. The role of trifluoroacetic acid, as well as, of the hydroxylamonium salt suggests a cooperative effect leading to high selective formation of 2-methyl-benzoxazoles. Graphical Abstract: One-pot TFA catalyzed synthesis of benzoxazoles starting from 2-hydroxyacetophenones. (Chemical Equation Presented).
- Rancan, Elia,Aric, Fabio,Quartarone, Giuseppe,Ronchin, Lucio,Vavasori, Andrea
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p. 939 - 946
(2015/08/06)
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- High-temperature synthesis of amides from alcohols or aldehydes by using flow chemistry
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An efficient conversion of aliphatic and aromatic alcohols or aldehydes into the corresponding primary amides was successfully achieved by using flow chemistry. Excellent yields were obtained in very short reaction times, and thus this method offers an efficient alternative to traditional methods for amide formation.
- Ambreen, Nida,Wirth, Thomas
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p. 7590 - 7593
(2015/04/22)
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- Reactions of 4-oxobenz[1,3-e]oxazinium perchlorates with α-aminoazoles
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Reactions of 4-oxo benz[1,3-e]oxazinium perchlorates with 1-R 1-3-R2-5-aminopyrazoles lead to the formation of derivatives of pyrazolo[3,4-d]pyrimidine and pyrazolo[1,5-a]1,3,5]triazine series, and with 3-amino-1,2,4-triazole, to [1,2,4]triazolo[1,5-a][1,3,5] triazines.
- Zamigailo,Petrova,Shirobokova,Lipson
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p. 288 - 293
(2013/07/26)
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- Methods of treatment of amyloidosis using bi-aryl aspartyl protease inhibitors
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The invention relates to novel compounds and methods of treating diseases, disorders, and conditions associated with amyloidosis. Amyloidosis refers to a collection of diseases, disorders, and conditions associated with abnormal deposition of A-beta protein.
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Page/Page column 25
(2010/02/15)
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- 2-AMINO- AND 2-THIO-SUBSTITUTED 1,3-DIAMINOPROPANES
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Disclosed are compounds of the formula: where variables Q, Z, X, R15, R2, R3, and Rc are defined herein. Compounds disclosed herein are inhibitors of the beta-secretase enzyme and are therefore useful in the treatment of Alzheimer’s disease and other diseases characterized by deposition of A beta peptide in a mammal.
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Page/Page column 253
(2008/06/13)
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- Synthesis and biological activity of novel 1,3-benzoxazine derivatives as K+ channel openers
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A new series of 1,3-benzoxazine derivatives with a 2-pyridine 1-oxide group at C4 was designed to explore novel K+ channel openers. Synthesis was carried out by using a palladium(0)-catalyzed carbon-carbon bond formation reaction of imino-triflates with organozinc reagents and via a new one-pot 1,3-benzoxazine skeleton formation reaction of benzoylpyridines. The compounds were tested for vasorelaxant activity in tetraethylammonium chloride (TEA) and BaCl2-induced and high KCl-induced contraction of rat aorta to identify potential K+ channel openers, and also for oral hypotensive effects in spontaneously hypertensive rats. An electron- withdrawing group with the proper shape at C6 and a methyl or halogens group at C7 of the 1,3-benzoxazine nucleus were required for the development of optimal vasorelaxant and hypotensive activity. In particular, 2-(6-bromo-7- chloro-2,2-dimethyl-2H-1,3-benzoxazin-4-yl)pyridine 1-oxide (71) showed more potent vasorelaxant activity (EC50=0.14 μM) against TEA and BaCL2- induced contraction and longer-lasting hypotensive effects than cromakalim (1).
- Yamamoto, Satoshi,Hashiguchi, Shohei,Miki, Shokyo,Igata, Yumiko,Watanabe, Toshifumi,Shiraishi, Mitsuru
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p. 734 - 745
(2007/10/03)
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