- A new synthesis for methyl 2-benzyloxylphenylacetate
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A new synthetic method for methyl 2-benzyloxylphenylacetate, a key intermediate of a new type of fungicides, had been found, which has only 3 steps. The 80% yield of the new method is a major improvement over the 30% 6- step-process reported by the literature.
- Wang, Zhongwen,Li, Zhengming,Liu, Tianlin,Ren, Jun
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Read Online
- Synthesis and bio-evaluation of natural butenolides-acrylate conjugates
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A series of novel 3-aryl-4-hydroxy-2(5H) furanone-acrylate hybrids were designed and synthesized based on the natural butenolides and acrylates scaffolds. The structures of the prepared compounds were characterized by 1H-NMR, 13C-NMR and electrospray ionization mass spectrometry (ESI-MS), and the bioactivity of the target compounds against twelve phytopathogenic fungi was investigated. The preliminary in vitro antifungal activity screening showed that most of the target compounds had moderate inhibition on various pathogenic fungi at the concentration of 100 mg·L?1, and presented broad-spectrum antifungal activities. Further studies also indicated that compounds 7e and 7k still showed some inhibitory activity against Pestallozzia theae, Sclerotinia sclerotiorum and Gibberella zeae on rape plants at lower concentrations, which could be optimized as a secondary lead for further research.
- Bao, Longzhu,Wang, Shuangshuang,Song, Di,Wang, Jingjing,Cao, Xiufang,Ke, Shaoyong
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- Dehydroxymethylation of alcohols enabled by cerium photocatalysis
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Dehydroxymethylation, the direct conversion of alcohol feedstocks as alkyl synthons containing one less carbon atom, is an unconventional and underexplored strategy to exploit the ubiquity and robustness of alcohol materials. Under mild and redox-neutral reaction conditions, utilizing inexpensive cerium catalyst, the photocatalytic dehydroxymethylation platform has been furnished. Enabled by ligand-to-metal charge transfer catalysis, an alcohol functionality has been reliably transferred into nucleophilic radicals with the loss of one molecule of formaldehyde. Intriguingly, we found that the dehydroxymethylation process can be significantly promoted by the cerium catalyst, and the stabilization effect of the fragmented radicals also plays a significant role. This operationally simple protocol has enabled the direct utilization of primary alcohols as unconventional alkyl nucleophiles for radical-mediated 1,4-conjugate additions with Michael acceptors. A broad range of alcohols, from simple ethanol to complex nucleosides and steroids, have been successfully applied to this fragment coupling transformation. Furthermore, the modularity of this catalytic system has been demonstrated in diversified radical-mediated transformations including hydrogenation, amination, alkenylation, and oxidation.
- Zhang, Kaining,Chang, Liang,An, Qing,Wang, Xin,Zuo, Zhiwei
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supporting information
p. 10556 - 10564
(2019/08/20)
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- Dehydroxymethylation of Alcohols Enabled by Cerium Photocatalysis
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Dehydroxymethylation, the direct conversion of alcohol feedstocks as alkyl synthons containing one less carbon atom, is an unconventional and underexplored strategy to exploit the ubiquity and robustness of alcohol materials. Under mild and redox-neutral reaction conditions, utilizing inexpensive cerium catalyst, the photocatalytic dehydroxymethylation platform has been furnished. Enabled by ligand-to-metal charge transfer catalysis, an alcohol functionality has been reliably transferred into nucleophilic radicals with the loss of one molecule of formaldehyde. Intriguingly, we found that the dehydroxymethylation process can be significantly promoted by the cerium catalyst, and the stabilization effect of the fragmented radicals also plays a significant role. This operationally simple protocol has enabled the direct utilization of primary alcohols as unconventional alkyl nucleophiles for radical-mediated 1,4-conjugate additions with Michael acceptors. A broad range of alcohols, from simple ethanol to complex nucleosides and steroids, have been successfully applied to this fragment coupling transformation. Furthermore, the modularity of this catalytic system has been demonstrated in diversified radical-mediated transformations including hydrogenation, amination, alkenylation, and oxidation.
- Zhang, Kaining,Chang, Liang,An, Qing,Wang, Xin,Zuo, Zhiwei
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supporting information
p. 10556 - 10564
(2019/08/28)
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- BISPHENOLATE TRANSITION METAL COMPLEXES, PRODUCTION AND USE THEREOF
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Bis phenolate transition metal complexes are disclosed for use in alkene polymerization, with optional chain transfer agent, to produce polyolefins.
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Page/Page column 37
(2019/02/15)
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- Palladium-Catalyzed Carbonylative Direct Transformation of Benzyl Amines under Additive-Free Conditions
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In this communication, we developed a new procedure for the direct carbonylative transformation of benzyl amines. Using dimethyl carbonate as the solvent, methyl 2-arylacetates can be produced in good to excellent yields from the corresponding primary, secondary, and tertiary benzyl amines with palladium as the catalyst. Notably, no base or any other additive is required here. In addition, our procedure can also be applied in the preparation of methylphenidate, which is a marketing drug and used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy.
- Li, Yahui,Wang, Zechao,Wu, Xiao-Feng
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p. 738 - 741
(2018/01/17)
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- A sustainable procedure toward alkyl arylacetates: Palladium-catalysed direct carbonylation of benzyl alcohols in organic carbonates
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A sustainable procedure for the synthesis of various alkyl arylacetates from benzyl alcohols has been developed. With palladium as the catalyst and organic carbonates as the green solvent and in situ activator, benzyl alcohols were carbonylated in an efficient manner without any halogen additives.
- Li, Yahui,Wang, Zechao,Wu, Xiao-Feng
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supporting information
p. 969 - 972
(2018/03/13)
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- Macrolide Synthesis through Intramolecular Oxidative Cross-Coupling of Alkenes
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A RhIII-catalyzed intramolecular oxidative cross-coupling between double bonds for the synthesis of macrolides is described. Under the optimized reaction conditions, macrocycles containing a diene moiety can be formed in reasonable yields and with excellent chemo- and stereoselectivity. This method provides an efficient approach to synthesize macrocyclic compounds containing a 1,3-conjugated diene structure.
- Jiang, Bing,Zhao, Meng,Li, Shu-Sen,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 555 - 559
(2018/02/21)
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- The computer-aided discovery of novel family of the 5-HT6 serotonin receptor ligands among derivatives of 4-benzyl-1,3,5-triazine
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The work describes a discovery of new chemical family of potent ligands for the 5-HT6 serotonin receptors. During the search for new histamine H4 receptor antagonists among 1,3,5-triazine derivatives, compound 2 (4-benzyl-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine) was found. Compound 2, weakly active for the H4 receptor but fitted in 3/4 of pharmacophore features of the 5-HT6R ligand, occurred to be a moderate 5-HT6R agent, useful as a lead structure for further modifications. A series of new derivatives (3–19) of the lead 2 was synthesized, evaluated in the radioligand binding assay (RBA) and explored in comprehensive molecular modelling, including both pharmacophore- and structure-based approaches with docking to the homology model of 5-HT6R. The most active compounds displayed a potent affinity for the 5-HT6R in the nanomolar range (Ki?=?20–30?nM), some of them (4, 11 and 19) were tested in the rat forced swim test that revealed their antidepressant-like effect. SAR-analysis on the basis of both, RBA and docking results, indicated that action on the receptor is related to the hydrophobicity and the size of aromatic moiety substituted by a methylene linker at the position 4 of 1,3,5-triazine.
- ?a?ewska, Dorota,Kurczab, Rafa?,Wi?cek, Ma?gorzata,Kamińska, Katarzyna,Sata?a, Grzegorz,Jastrz?bska-Wi?sek, Magdalena,Partyka, Anna,Bojarski, Andrzej J.,Weso?owska, Anna,Kie?-Kononowicz, Katarzyna,Handzlik, Jadwiga
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supporting information
p. 117 - 124
(2017/04/26)
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- Discovery, synthesis, and structure-activity relations of 3,4-dihydro-1H-spiro(naphthalene-2,2′-piperidin)-1-ones as potassium-competitive acid blockers
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With the aim to discover a gastric antisecretory agent more potent than the existing proton pump inhibitors, novel 3,4-dihydro-1H-spiro(naphthalene-2,2′-piperidin)-1-one derivatives, which could occupy two important lipophilic pockets (described as LP-1 and LP-2) of H+,K+-ATPase and can strongly bind to the K+-binding site, were designed based on a docking model. Among the compounds synthesized, compound 4d showed a strong H+,K+-ATPase-inhibitory activity and a high stomach concentration in rats, resulting in potent inhibitory action on histamine-stimulated gastric acid secretion in rats. Furthermore, 4d exerted significant inhibitory action on histamine-stimulated gastric-acid secretion in rats with a rapid onset and moderate duration of action after the administration. These findings may lead to a new insight into the drug design of potassium-competitive acid blockers.
- Imaeda, Toshihiro,Ono, Koji,Nakai, Kazuo,Hori, Yasunobu,Matsukawa, Jun,Takagi, Terufumi,Fujioka, Yasushi,Tarui, Naoki,Kondo, Mitsuyo,Imanishi, Akio,Inatomi, Nobuhiro,Kajino, Masahiro,Itoh, Fumio,Nishida, Haruyuki
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p. 3719 - 3735
(2017/06/13)
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- O-methoxyphenylacetic acid Schiff base and synthesis method and application thereof
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The invention relates to o-methoxyphenylacetic acid Schiff base and a synthetic method and an application thereof, wherein R1 represents hydrogen, hydroxyl, nitryl or bromine, R2 represents hydrogen or nitryle, and R3 represents hydrogen, methoxyl, nitryl, chlorine or hydroxyl. The compound provided by the invention has remarkable inhibiting effect on escherichia coli, staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa, and the minimal inhibitory concentration can reach 12.5 microgram/mL, so that the compound can be used as a bacteriostatic agent.
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Page/Page column 5-7
(2020/02/10)
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- Synthesis of Psoralidin derivatives and their anticancer activity: First synthesis of Lespeflorin I1
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Synthetic scheme for the preparation of a number of different derivatives of anticancer natural product Psoralidin is described. A convergent synthetic approach is followed using simple starting materials like substituted phenyl acetic esters and benzoic acids. The developed synthetic route leads us to complete the first synthesis of an analogous natural product Lespeflorin I1, a mild melanin synthesis inhibitor. Preliminary bioactivity studies of the synthesized compounds are carried out against two commonly used prostate cancer cell lines. Results show that the bioactivity of the compounds can be manipulated by the simple modification of the functional groups.
- Pahari, Pallab,Saikia, Ujwal Pratim,Das, Trinath Prasad,Damodaran, Chendil,Rohr, Jürgen
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supporting information
p. 3324 - 3334
(2016/05/19)
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- Ultrasound-Assisted Methyl Esterification of Carboxylic Acids ACatalyzed by Polymer-Supported Triphenylphosphine
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A convenient and efficient sonochemical method for methyl esterification of carboxylic acids catalyzed by polymer-supported triAphenylphosphine (PS-Ph3P) is reported. In the presence of 1:0.1:2 molar ratio of 2,4,6-trichloro-1,3,5-triazine/PS-Ph3P/Na2CO3, methyl esters of various carboxylic acids bearing reactive hydroxyl groups as well as acid-or base-labile functionalities could be rapidly prepared (within 10-20 min) in good to excellent yields without necessity to pre-activate the acids. Using the polymer-bound phosphine also allows easy isolation of the products which, in most of the cases, were obtained in high purities without column chromatography.
- Jaita, Subin,Phakhodee, Wong,Pattarawarapan, Mookda
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p. 2006 - 2008
(2015/09/01)
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- Acetylcholinesterase inhibition activity of some quinolinyl substituted triazolothiadiazole derivatives
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A series of aralkanoic acids was converted into aralkanoic acid hydrazides through their esters formation. The aralkanoic acid hydrazides upon treatment with carbon disulfide and methanolic potassium hydroxide yielded potassium dithiocarbazinate salts, which on refluxing with aqueous hydrazine hydrate yielded 5-aralkyl-4-amino-3-mercapto-1,2,4-triazoles. The target compounds, 3-aralkyl-6-(substitutedquinolinyl) [1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles, were synthesized by condensing various quinolinyl substituted carboxylic acids with 5-aralkyl-4-amino-3-mercapto-1,2,4-triazoles in phosphorus oxychloride. The structures of the newly synthesized triazolothiadiazoles were characterized by IR, 1H NMR, 13C NMR, and elemental analysis studies. The structure of one of the 5-aralkyl-4-amino-3-mercapto-1,2,4-triazoles was unambiguously deduced by single crystal X-ray diffraction analysis. All the synthesized compounds were screened for their acetylcholinesterase inhibition activities. Four of the triazolothiadiazoles exhibited excellent acetylcholinesterase inhibition activities as compared to the reference inhibitor.
- Rafiq, Muhammad,Saleem, Muhammad,Hanif, Muhammad,Abbas, Qamar,Lee, Ki Hwan,Seo, Sung-Yum
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p. 170 - 177
(2015/04/14)
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- Similarities and differences in the crystal packing of methoxybenzyl and methoxyphenylethyl-1,3,4-oxadiazole-2(3H)-thiones
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This work reports the crystal and molecular structures of five 1,3,4-oxadiazol-2(3H)-thiones derived from 2, 3 and 4-methoxy substituted 2-phenylacetic acid and 2- and 4-methoxy substituted 3-phenylpropanoic acid. The methoxybenzyl-1,3,4-oxadiazol-2(3H)-thiones are V-shaped while the corresponding methoxyphenylethyl-systems are close to planar, which impacts the solid state molecular packing arrangement. For molecules 1-4, inversion related N-H...S hydrogen bonds generating R22(8) rings dominate the packing, supported by an eclectic mix of C-H...O, C-H...S, C-H...π and π...π contacts that stack the molecules into interconnected columns. In contrast, each of the two unique molecules in the asymmetric unit of 5 forms N-H...O contacts with like molecules augmented by C-H...S contacts for one molecule and C-H...O contacts for the other to generate planar layers that are interconnected though a series of π...π stacking interactions. The Royal Society of Chemistry.
- Khan, Imtiaz,Ibrar, Aliya,Simpson, Jim
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p. 164 - 174
(2014/01/06)
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- Synthesis, urease inhibition, antioxidant and antibacterial studies of some 4-Amino-5-aryl-3H-1,2,4-triazole-3-thiones and their 3,6-Disubstituted 1,2,4-Triazolo[3,4-b]1,3,4-thiadiazole derivatives
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A new series of 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones, bearing various methoxybenzyl- and methoxyphenethyl groups, was synthesized by refluxing potassium hydrazinecarbodithioate salts in dilute aqueous solution of hydrazine hydrate. These salts were formed by the reaction of acid hydrazides and carbon disulfide in methanolic potassium hydroxide solution at 0-5 °C. 4-Amino-5-aryl-3H-1,2,4-triazole-3-thiones were condensed with different substituted aromatic acids to yield 3,6-disubstituted-1,2,4-triazolo[3,4-b]1,3, 4-thiadiazoles. The structures of the synthesized compounds were characterized by infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), elemental analysis and mass spectrometric (MS) studies. All the synthesized compounds were screened for their urease inhibition, antioxidant and antibacterial activities. Some compounds showed excellent urease inhibition activity, more than the standard drug. Others exhibited potent antioxidant activity. All the compounds showed significant antibacterial activities as compared to the standard drug.
- Hanif, Muhammad,Saleem, Muhammad,Hussain, Muhammad Tahir,Rama, Nasim Hasan,Zaib, Sumera,Aslam, Muhammad Adil M.,Jones, Peter G.,Iqbal, Jamshed
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experimental part
p. 854 - 860
(2012/07/28)
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- Palladium-catalyzed asymmetric synthesis of 2-pyrrolidinones with a quaternary carbon stereocenter
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A palladium-catalyzed asymmetric synthesis of 2-pyrrolidinones with a quaternary stereocenter at the 3-position has been achieved by the reaction of γ-methylidene-δ-valerolactones with alkyl isocyanates. High enantioselectivity has been realized by employing a newly synthesized chiral phosphoramidite ligand. The Royal Society of Chemistry 2012.
- Shintani, Ryo,Ito, Tomoaki,Nagamoto, Midori,Otomo, Haruka,Hayashi, Tamio
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supporting information
p. 9936 - 9938
(2012/10/29)
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- Synthesis, crystal structure and b-glucuronidase inhibition activity of some new hydrazinecarboxamides and their 1,2,4-triazole derivatives
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A new series of hydrazinecarboxamides (5a-n), bearing various methoxyphenyl and methoxyphenethyl groups, was synthesized by condensation of corresponding acid hydrazides (3a-f) with methoxyphenylisocyanates (4a-c). Dehydrocyclization of hydrazinecarboxamides (5a-n) yielded corresponding methoxyphenyl and methoxyphenethyl substituted triazoles (6a-l) by refluxing in 2 N aqueous sodium hydroxide solution. All the synthesized compounds were screened for their b-glucuronidase inhibition activity. Compounds 5a, 5e, 5h, and 5l exhibited an excellent b-glucuronidase inhibitory activity as compared to the standard inhibitor. Springer Science+Business Media, LLC 2011.
- Hanif, Muhammad,Khan, Imtiaz,Rama, Nasim Hasan,Noreen, Shagufta,Choudhary, Muhammad Iqbal,Jones, Peter G.,Iqbal, Mazhar
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p. 3885 - 3896
(2013/02/23)
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- Inhibitors of semicarbazide-sensitive amine oxidase (SSAO) and VAP-1 mediated adhesion useful for treatment and prevention of diseases
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Compositions and methods of using compositions for treatment of inflammatory diseases and immune disorders are provided. Allylamino compounds are disclosed which are inhibitors of semicarbazide-sensitive amine oxidase (SSAO) and/or vascular adhesion protein 1 (VAP-1). The compounds have therapeutic utility in suppressing inflammation and inflammatory responses, and in treatment of several disorders, including multiple sclerosis and stroke.
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Page/Page column 67
(2008/06/13)
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- MODULATORS OF ATP-BINDING CASSETTE TRANSPORTERS
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The present invention relates to modulators of ATP-Binding Cassette ("ABC") transporters or fragments thereof, including Cystic Fibrosis Transmembrane Conductance Regulator ("CFTR"), compositions thereof, and methods therewith. The present invention also relates to methods of treating ABC transporter mediated diseases using such modulators (I) or a pharmaceutically acceptable salt thereof, wherein: Ht is a 5-membered heteroaromatic ring containing 1-4 heteroatoms selected from O, S, N or NH, wherein said ring is optionally fused to a 6-membered monocyclic or 10-membered bicyclic carbocyclic or heterocyclic, aromatic or non-aromatic ring, wherein Ht is optionally substituted with w occurrences of -WRw, wherein w is 0-5; ring A is 3-7 membered monocyclic ring having 0-3 heteroatoms selected from O, S, N, or NH, wherein ring A is optionally substituted with q occurrences of QRQ; ring B is optionally fused to 5-6 membered carbocyclic or heterocyclic, aromatic or non-aromatic ring .
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Page/Page column 138-139
(2010/02/13)
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- An improved and versatile method for the rapid synthesis of aryldihydrobenzofuran systems by a boron tribromide-mediated cyclization reaction
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Boron tribromide is presented as a highly reactive reagent that simultaneously allows the demethylation and fully diastereoselective cyclization of different precursor molecules, obtained by an aldol-type reaction, to a series of hydroxylated aryldihydrobenzofuran systems in racemic form. The latter are often found as key structures in natural compounds of different classes. Syntheses of educts, which mainly took advantage of a versatile Rieche formylation, are also described.
- Detterbeck, Richard,Hesse, Manfred
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p. 343 - 360
(2007/10/03)
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- New and efficient method for esterification of carboxylic acids with simple primary and secondary alcohols using cerium(IV) ammonium nitrate (CAN)
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The esterification of phenylacetic acids and cis-oleic acid with primary and secondary simple alcohols, which also act as solvents using cerium(IV) ammonium nitrate (CAN) at room temperature gave phenylacetates and methyl (9Z)-octadec-9-enoate. The reactions, which occur under relatively mild conditions, afforded the desired products in good to excellent yields.
- Pan, Wen-Bin,Chang, Fang-Rong,Wei, Li-Mei,Wu, Ming-Jung,Wu, Yang-Chang
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p. 331 - 334
(2007/10/03)
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- The effect of an alkoxy group on the kinetic and thermodynamic acidity of benzene and toluene
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2-, 3- and 4-Methoxytoluene can be selectively metalated at an O-adjacent ortho position when butyllithium or tert-butyllithium in the presence of sodium (potassium) tert-butoxide or N,N,N',N'',N''-pentamethyldiethylenetriamine are employed as reagents. In contrast, lithium diisopropylamide or lithium 2,2,6,6-tetramethylpiperidide deprotonate the benzylic α-position of 2- and 3-methoxytoaluene exclusively and of 4-methoxytoluene preferentially. These relative reactivities can be rationalized by an interplay of transition state stabilizing and destabilizing forces (dipole matching and metal coordination vs. lone pair repulsion).
- Schlosser, Manfred,Maccaroni, Paola,Marzi, Elena
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p. 2763 - 2770
(2007/10/03)
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- 6-substituted pyrazolo (3,4-d)pyrimidin-4-ones and compositions and methods of use thereof
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6-Substituted pyrazolo[3,4 -d]pyrimidin-4-one derivatives, pharmaceutical compositions containing them and methods for effecting c-GMP-phosphodiesterase inhibition and for treating heart failure and/or hypertension.
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- Solid-Phase Synthetic Methods in Combinatorial Chemistry
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The gel-phase carbon NMR spectra of various polymer supports are evaluated as to their suitability in the production of non-peptide combinatorial libraries. The solid-phase synthesis of biphenyls as scaffolds for the production of combinatorial libraries is also described. Both substituted and unsubstituted trialkylphenyltins were shown to undergo heterogenous palladium-catalyzed Stille coupling with aryl electrophiles to give after photolytic cleavage using the NpSSMpact linker biphenyls containing no residual amide, carboxylic acid, or alcohol appendages.
- Sucholeiki, Irving
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p. 618 - 630
(2007/10/03)
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- Solid-Phase Photochemical C-S Bond Cleavage Of Thioethers - A New Approach To The Solid-Phase Production Of Non-Peptide Molecules.
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Thioethers can readily be used as a method for attachment of organic molecules to solid supports and can undergo light induced heterogeneous C-S bond cleavage upon irradiation with 350 nm light.
- Sucholeiki, Irving
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p. 7307 - 7310
(2007/10/02)
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- Polymeric dicarbonyl ruthenium(I) acetate - An efficient catalyst for alkene cyclopropanation with diazoacetates
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The polymeric complex [Ru2(CO)4(μ-OAc)2](n) is the first Ru(I) catalyst that efficiently catalyzes cyclopropanation of alkenes with diazoacetic esters. The related dinuclear catalyst Ru2(CO)4(μ-OAc)2(MeCN)2 shows a similar performance only for cyclopropanation of monosubstituted alkenes.
- Maas,Werle,Alt,Mayer
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p. 881 - 888
(2007/10/02)
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- Benzothiazepines
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A compound selected from the group consisting of all possible isomeric forms, racemic or optically active of a compound of the formula STR1 wherein the substituents are defined in the specification, and their non-toxic, pharmaceutically acceptable acid addition salts having antiarhythmic activity.
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- Novel arylacetic acid derivatives
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A compound having a potentially inhibitory effect on 15-hydroxy-prostaglandin dehydrognase (PGDH) and having the formula STR1 in which R1 and R2 are hydrogen or lower alkyl; R3 is hydrogen, lower alkyl or substituted or unsubstituted phenyl; R4, R5, and R6 are hydrogen, halogen, lower alkyl, lower alkoxy, cyano, carboxy or nitro; at least one of the groups R4 to R6 being hydrogen; R7 to R11 are hydrogen, halogen, cyano, lower alkyl, trifluoromethyl, lower alkoxy, hydroxy, lower acyl, lower alkoxycarbonyl, N,N,-diloweralkyl-aminocarbonyl or N,N-loweralkylene-aminocarbonyl; and R8 and R10 may in addition be carboxy; at least two of R7 to R11 always being hydrogen; and --A-- is --CO--, --CH2 --CO--, --CH=CH--, --CH=CH--CO-- or corresponding groups in which a hydrogen atom is replaced by a lower alkyl group. The invention comprises also lactones of those compounds in which R1 is hydrogen, and salts of those compounds which contain at least one carboxy group.
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- The Total Synthesis of (15R)- and (15S)-16-Hydroxyferruginol
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In order to assign the absolute configuration of C-15 in natural 16-hydroxyferruginol, (5S,10S,15R)-(1a) and (5S,10S,15S)-8,11,13-abietatriene-12-16-diol (1b) have been synthesized.Optical resolution of 2-(2-methoxyphenyl)propanoic acid, prepared from methyl (2-methoxyphenyl)acetate, with cinchonidine afforded (R)- and (S)-enantiomers, which were converted into triphenylphosphonium chloride (3a) and its (S)-isomer (3b) respectively.The Wittig reaction of (R)-(-)-α-cyclocitral with 3a, followed by partial catalytic hydrogenation and intramolecular cyclization gave (5S,10S,15R)-12,16-dimethoxy-8,11,13-abietatriene (16a) together with its (5S,10R,15R)-isomer.Similary, 3b was also converted into (5S,10S,15S)-12,13-dimethoxy-8,11-abietatriene (6b) and its (5S,10R,15R)-isomer.Demethylation of 16a gave 1a which was identical with natural 16-hydroxyferruginol.The dimethoxy compound 16b was also demethylated to give 1b.
- Matsumoto, Takashi,Imai, Sachihiko,Miuchi, Shigekazu,Sugibayashi, Hidenori
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p. 340 - 345
(2007/10/02)
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- Conversion of Aromatic Ketones into α-Arylalkanoic Acids. Oxidation by Thallium(III) and by Halogens
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The mechanism by which thallium (III) nitrate oxidises aromatic ketones to α-arylalkanoic acids has been investigated and the role of additives in the system elucidated.It is found that in the absence of additives an organothallium intermediate, most probably the phenacylthallium species BzCH2Tl(NO3)2, persists and that the key to an efficient rearrangement is the ready conversion of this compound into its acetal.Thallium(III) is shown not to be a unique reagent for the oxidation.Other oxidants capable of acting initially as an electrophile and then as a leaving group are equally effective, provided that formation of an acetal is possible.Iodine-silver nitrate in particular offers considerable advantages as reagent over thallium(III).Higher specificity is achieved, unwanted side-reactions can be avoided, and toxicity problems are eliminated.Bromine may be used instead of iodine, but chlorine proves unsatisfactory as an oxidant.
- Higgins, Stanley D.,Thomas, Barry C.
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p. 235 - 242
(2007/10/02)
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- Esters of α-Arylalkanoic Acids from 'Masked' α-Halogenoalkyl Aryl Ketones and Silver Salts: Synthetic, Kinetic, and Mechanistic Aspects
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A method for the synthesis of alkyl esters of α-arylalkanoic acids is given based on silver-ion-assisted (AgBF4, AgOSO2CF3, AgSbF6, AgNO3) solvolysis of alkyl acetals of primary and secondary α-halogenoalkyl aryl ketones (Hal = I, Br, Cl) in an alcoholic medium (methanol, ethanol).The reaction is quite selective and alkyl esters are the only reaction products; ethers, which are possible substitution products, are not found.The importance of masking the carbonyl as the acetal is emphasised.The reaction is found to be first-order in AgBF4 and in the primary α-halogeno acetal.A three-point Hammett correlation (ρ = -3.29) between ?+ and the rate constants suggests a large cationic contribution as well as strong aryl participation in the transition state.The role payed by the oxygen of the acetal group in the specificity of the reaction is discussed in comparison with the reactivity of analogous compounds with saturated skeletons and of α-halogenoalkyl aryl ketones.
- Giordano, Claudio,Castaldi, Graziano,Casagrande, Francesco,Belli, Aldo
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p. 2575 - 2582
(2007/10/02)
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