- Continuous-Flow Hofmann Rearrangement Using Trichloroisocyanuric Acid for the Preparation of 2-Benzoxazolinone
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A continuous-flow preparation of 2-benzoxazolinone via the Hofmann rearrangement of salicylamide has been implemented employing trichloroisocyanuric acid as the stable and atom-economic chlorinating agent. The system was optimized to avoid solid accumulation and allow the preparation of hundreds of grams of the pure desired material over a working day. Furthermore, a trichloroisocyanuric acid (TCCA)-based chlorination of 2-benzoxazolone to the corresponding 5-chloro derivative was also carried out under batch conditions.
- Gambacorta, Guido,Baxendale, Ian R.
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p. 422 - 430
(2022/02/01)
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- 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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- Structure-activity relationship of salicylic acid derivatives on inhibition of TNF-α dependent NFκB activity: Implication on anti-inflammatory effect of N-(5-chlorosalicyloyl)phenethylamine against experimental colitis
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To develop a more potent NFκB inhibitor from salicylic acid which is known to inhibit activity of NFκB, a transcription factor regulating genes involved in immunity, inflammation and tumorigenesis, derivatives of salicylic acid (SA) where the 5 position, carboxyl or hydroxyl group was modified were treated in HCT116 cells transfected with an NFκB dependent luciferase gene and LPS-stimulated RAW264.7 cells. Amidation of the carboxylic group or substitution of chlorine at the 5 position increased the ability of SA to suppress the expression of NFκB dependent luciferase and inducible nitric oxide synthase, a product of an NFκB target gene. Moreover, simultaneous amidation and chlorination of SA (5-chlorosalicylamide; 5-CSAM) conferred an additive NFκB inhibitory activity on SA. To further enhance the inhibitory activity, N-modification was imposed on 5-CSAM. N-(5-chlorosalicyloyl) phenethylamine (5-CSPA), N-(5-chlorosalicyloyl)3-phenylpropylamine (5-CSPPA) and N-(5-chlorosalicyloyl)4-hydroxyphenylethylamine (5-CSHPA) showed greater potencies for inhibiting NFκB activity than other derivatives. Their IC50s' in the luciferase assay measured 15 μM (5-CSPA), 17 μM (5-CSPPA) and 91 μM (5-CSHPA). Rectal administration of 5-CSPA ameliorated TNBS-induced rat colitis, which was more effective than a conventional drug, 5-aminosalicylic acid. These data may provide useful information for development of a therapeutic agent for treatment of diseases where NFκB plays a critical role in the pathogenic progresses.
- Kim, Jihye,Kang, Sookjin,Hong, Sungchae,Yum, Soowhan,Kim, Young Mi,Jung, Yunjin
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experimental part
p. 36 - 44
(2012/03/26)
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- PREPARATION OF 4-SUBSTITUTED 2-AMINO-BENZO[4,5]FURO [3,2-D]PYRIMIDINE DERIVATIVES
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The present invention is directed to a process for the preparation of a compound of formula (I), wherein R1, R2 and X have the meaning as indicated in the description and claims. Said compounds are useful as key intermediates for the preparation of the related pharmaceutically active compounds or as active compounds.
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Page/Page column 12
(2008/12/05)
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- Method of preparing salicylamides
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The present invention provides a fast, high yield method for preparing salicylamide intermediates. The method comprises reacting a C4 or higher alkyl ester of salicylic acid or derivative thereof with at least one amine selected from the group consisting of monoalkylamines, dialkylamines, ammonia, and any combination of any of the foregoing in alcohol to yield the sali-cylamide. The C4 or higher alkyl ester of salicylic acid or a derivative thereof is preferably prepared by reacting salicylic acid or a derivative thereof with a C4 or higher alcohol in presence of at least one of sulfuric acid, a sulfonic acid, and a mineral acid. This process for preparing salicylamide intermediates from salicylic acid or derivative thereof generally has a cycle time of about 2 days, and yields about 95% of a 99% pure material. In comparison, when a C3 or lower alkyl ester is used in lieu of the C4 or higher alkyl ester, the process generally has a cycle time of 7-9 days and yields about 60% of a 95% pure material. Methods of preparing an alkylated salicylamide are also provided.
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Page/Page column 7-8
(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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