- Catalytic α-Deracemization of Ketones Enabled by Photoredox Deprotonation and Enantioselective Protonation
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This study reports the catalytic deracemization of ketones bearing stereocenters in the α-position in a single reaction via deprotonation, followed by enantioselective protonation. The principle of microscopic reversibility, which has previously rendered this strategy elusive, is overcome by a photoredox deprotonation through single electron transfer and subsequent hydrogen atom transfer (HAT). Specifically, the irradiation of racemic pyridylketones in the presence of a single photocatalyst and a tertiary amine provides nonracemic carbonyl compounds with up to 97% enantiomeric excess. The photocatalyst harvests the visible light, induces the redox process, and is responsible for the asymmetric induction, while the amine serves as a single electron donor, HAT reagent, and proton source. This conceptually simple light-driven strategy of coupling a photoredox deprotonation with a stereocontrolled protonation, in conjunction with an enrichment process, serves as a blueprint for other deracemizations of ubiquitous carbonyl compounds.
- Chen, Shuming,Gao, Anthony Z.,Ivlev, Sergei I.,Meggers, Eric,Nie, Xin,Ye, Chen-Xi,Zhang, Chenhao
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supporting information
p. 13393 - 13400
(2021/09/03)
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- Harnessing Applied Potential: Selective β-Hydrocarboxylation of Substituted Olefins
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The construction of carboxylic acid compounds in a selective fashion from low value materials such as alkenes remains a long-standing challenge to synthetic chemists. In particular, β-addition to styrenes is underdeveloped. Herein we report a new electrosynthetic approach to the selective hydrocarboxylation of alkenes that overcomes the limitations of current transition metal and photochemical approaches. The reported method allows unprecedented direct access to carboxylic acids derived from β,β-trisubstituted alkenes, in a highly regioselective manner.
- Alkayal, Anas,Buckley, Benjamin R.,Malkov, Andrei V.,Montanaro, Stephanie,Tabas, Volodymyr,Wright, Iain A.
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supporting information
(2020/02/13)
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- Mechanistic Investigation of the Nickel-Catalyzed Carbonylation of Alcohols
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The carbonylation of alcohols represents a straightforward and atom-efficient methodology for the preparation of carboxylic acids. It is desirable to perform these reactions under precious metal-free and low-pressure conditions, with regioselectivity control. In this work, we present a detailed mechanistic study of a catalytic system based on NiI2, which can carbonylate benzylic alcohols in a highly regioselective manner to the corresponding branched carboxylic acids, core motifs for nonsteroidal drugs. The combination of catalytic amounts of nickel and iodide is crucial for efficient catalytic and regioselective conversion. Quantum-chemical computations were used to evaluate the underlying mechanistic processes. They revealed that a combination of two mechanisms is responsible for the observed reactivity and that the oxidative addition of alkyl halides to the Ni(0) species follows a radical oxidation pathway via two one-electron steps.
- Comba, Peter,Ghosh, Tamal,Hashmi, A. Stephen K.,Krieg, Saskia,Menche, Maximilian,Paciello, Rocco,Rück, Katharina S. L.,Sabater, Sara,Sch?fer, Ansgar,Schaub, Thomas
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supporting information
(2020/03/19)
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- 1,3,2-Diazaphospholenes Catalyze the Conjugate Reduction of Substituted Acrylic Acids
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The potent nucleophilicity and remarkably low basicity of 1,3,2-diazaphospholenes (DAPs) is exploited in a catalytic, metal-free 1,4-reduction of free α,β-unsaturated carboxylic acids. Notably, the reduction occurs without a prior deprotonation of the carboxylic acid moiety and hence does not consume an additional hydride equivalent. This highlights the excellent nucleophilic character and low basicity of DAP-hydrides. Functional groups such as Cbz group or alkyl halides which can be problematic with classical transition-metal catalysts are well tolerated in the DAP-catalyzed process. Moreover, the transformation is characterized by a low catalyst loading, mild reaction conditions at ambient temperature as well as fast reaction times and high yields. The proof-of-principle for a catalytic enantioselective version is described.
- Reed, John H.,Cramer, Nicolai
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p. 4262 - 4266
(2020/07/13)
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- Photocarboxylation of Benzylic C-H Bonds
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The carboxylation of sp3-hybridized C-H bonds with CO2 is a challenging transformation. Herein, we report a visible-light-mediated carboxylation of benzylic C-H bonds with CO2 into 2-arylpropionic acids under metal-free conditions. Photo-oxidized triisopropylsilanethiol was used as the hydrogen atom transfer catalyst to afford a benzylic radical that accepts an electron from the reduced form of 2,3,4,6-tetra(9H-carbazol-9-yl)-5-(1-phenylethyl)benzonitrile generated in situ. The resulting benzylic carbanion reacts with CO2 to generate the corresponding carboxylic acid after protonation. The reaction proceeded without the addition of any sacrificial electron donor, electron acceptor or stoichiometric additives. Moderate to good yields of the desired products were obtained in a broad substrate scope. Several drugs were successfully synthesized using the novel strategy.
- Meng, Qing-Yuan,Schirmer, Tobias E.,Berger, Anna Lucia,Donabauer, Karsten,K?nig, Burkhard
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supporting information
p. 11393 - 11397
(2019/08/20)
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- Site-Selective, Remote sp3 C?H Carboxylation Enabled by the Merger of Photoredox and Nickel Catalysis
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A photoinduced carboxylation of alkyl halides with CO2 at remote sp3 C?H sites enabled by the merger of photoredox and Ni catalysis is described. This protocol features a predictable reactivity and site selectivity that can be modulated by the ligand backbone. Preliminary studies reinforce a rationale based on a dynamic displacement of the catalyst throughout the alkyl side chain.
- Sahoo, Basudev,Bellotti, Peter,Juliá-Hernández, Francisco,Meng, Qing-Yuan,Crespi, Stefano,K?nig, Burkhard,Martin, Ruben
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supporting information
p. 9001 - 9005
(2019/06/24)
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- Electrogenerated Sm(II)-Catalyzed CO2 Activation for Carboxylation of Benzyl Halides
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Sm(II)-catalyzed carboxylation of benzyl halides is reported through the electrochemical reduction of CO2. The transformation proceeds under mild reaction conditions to afford the corresponding phenylacetic acids in good to excellent yields. This user-friendly and operationally simple protocol represents an alternative to traditional strategies, which usually proceeds through the C(sp3)-halide activation pathway.
- Bazzi, Sakna,Schulz, Emmanuelle,Mellah, Mohamed
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supporting information
p. 10033 - 10037
(2019/12/24)
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- Biocatalytic Parallel Interconnected Dynamic Asymmetric Disproportionation of α-Substituted Aldehydes: Atom-Efficient Access to Enantiopure (S)-Profens and Profenols
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The biocatalytic asymmetric disproportionation of aldehydes catalyzed by horse liver alcohol dehydrogenase (HLADH) was assessed in detail on a series of racemic 2-arylpropanals. Statistical optimization by means of design of experiments (DoE) allowed the identification of critical interdependencies between several reaction parameters and revealed a specific experimental window for reaching an ′optimal compromise′ in the reaction outcome. The biocatalytic system could be applied to a variety of 2-arylpropanals and granted access in a redox-neutral manner to enantioenriched (S)-profens and profenols following a parallel interconnected dynamic asymmetric transformation (PIDAT). The reaction can be performed in aqueous buffer at ambient conditions, does not rely on a sacrificial co-substrate, and requires only catalytic amounts of cofactor and a single enzyme. The high atom-efficiency was exemplified by the conversion of 75 mM of rac-2-phenylpropanal with 0.03 mol% of HLADH in the presence of ～0.013 eq. of oxidized nicotinamide adenine dinucleotide (NAD+), yielding 28.1 mM of (S)-2-phenylpropanol in 96% ee and 26.5 mM of (S)-2-phenylpropionic acid in 89% ee, in 73% overall conversion. Isolated yield of 62% was obtained on 100 mg-scale, with intact enantiopurities. (Figure presented.).
- Tassano, Erika,Faber, Kurt,Hall, Mélanie
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supporting information
p. 2742 - 2751
(2018/07/29)
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- Regioselectivity inversion tuned by iron(iii) salts in palladium-catalyzed carbonylations
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Impactful regioselectivity control is crucial for cost-effective chemical synthesis. By using cheap and abundant iron(iii) salts, the hydroxycarbonylations of both aromatic and aliphatic alkenes were significantly enhanced in both reactivity and selectivity (iso/n or n/iso up to >99:1). Moreover, Pd-catalyzed carbonylation selectivity can be switched from branched to linear by using different Fe(iii) salts. In addition, similar results were obtained for the carbonylation of secondary alcohols.
- Huang, Zijun,Cheng, Yazhe,Chen, Xipeng,Wang, Hui-Fang,Du, Chen-Xia,Li, Yuehui
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supporting information
p. 3967 - 3970
(2018/04/23)
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- Ligand-Controlled Regioselective Hydrocarboxylation of Styrenes with CO2 by Combining Visible Light and Nickel Catalysis
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The ligand-controlled Markovnikov and anti-Markovnikov hydrocarboxylation of styrenes with atmospheric pressure of CO2 at room temperature using dual visible-light-nickel catalysis has been developed. In the presence of neocuproine as ligand, the Markovnikov product is obtained exclusively, while employing 1,4-bis(diphenylphosphino)butane (dppb) as the ligand favors the formation of the anti-Markovnikov product. A range of functional groups and electron-poor, -neutral, as well as electron-rich styrene derivatives are tolerated by the reaction, providing the desired products in moderate to good yields. Preliminary mechanistic investigations indicate the generation of a nickel hydride (H-NiII) intermediate, which subsequently adds irreversibly to styrenes.
- Meng, Qing-Yuan,Wang, Shun,Huff, Gregory S.,Konig, Burkhard
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supporting information
p. 3198 - 3201
(2018/03/13)
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- Synthesis of Bicyclo[n.1.0]alkanes by a Cobalt-Catalyzed Multiple C(sp3)?H Activation Strategy
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A cobalt-catalyzed dual C(sp3)?H activation strategy has been developed and it provides a novel strategy for the synthesis of bicyclo[4.1.0]heptanes and bicyclo[3.1.0]hexanes. A key to the success of this reaction is the conformation-induced methylene C(sp3)?H activation of the resulting cobaltabicyclo[4.n.1] intermediate. In addition, the synthesis of bicyclo[3.1.0]hexane from pivalamide, by a triple C(sp3)?H activation, has also been demonstrated.
- Zhang, Zhuo-Zhuo,Han, Ye-Qiang,Zhan, Bei-Bei,Wang, Sai,Shi, Bing-Feng
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supporting information
p. 13145 - 13149
(2017/09/28)
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- Enantioselective Decarboxylative Cyanation Employing Cooperative Photoredox Catalysis and Copper Catalysis
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The merger of photoredox catalysis with asymmetric copper catalysis have been realized to convert achiral carboxylic acids into enantiomerically enriched alkyl nitriles. Under mild reaction conditions, the reaction exhibits broad substrate scope, high yields and high enantioselectivities. Furthermore, the reaction can be scaled up to synthesize key chiral intermediates to bioactive compounds.
- Wang, Dinghai,Zhu, Na,Chen, Pinhong,Lin, Zhenyang,Liu, Guosheng
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supporting information
p. 15632 - 15635
(2017/11/14)
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- Cp2TiCl2-Catalyzed Regioselective Hydrocarboxylation of Alkenes with CO2
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Cp2TiCl2-catalyzed regioselective hydrocarboxylation of alkenes with CO2 to give carboxylic acids in high yields has been developed in the presence of iPrMgCl. The reaction proceeds with a wide range of alkenes under mild conditions. Styrene and its derivatives can transform to α-aryl carboxylic acids, and aliphatic alkenes can transform to form alkanoic acids.
- Shao, Peng,Wang, Sheng,Chen, Chao,Xi, Chanjuan
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supporting information
p. 2050 - 2053
(2016/06/01)
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- Development of a novel electrochemical carboxylation system using a microreactor
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We have developed a novel electrochemical carboxylation system for CO2 fixation to benzyl halides using a microreactor. In this system, electrochemical carboxylation of benzyl halides proceeded very efficiently without the use of a sacrificial anode such as a Mg anode to give carboxylated products in excellent yields.
- Tateno, Hiroyuki,Matsumura, Yoshimasa,Nakabayashi, Koji,Senboku, Hisanori,Atobe, Mahito
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p. 98721 - 98723
(2015/12/05)
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- A versatile synthesis of O-desmethylangolensin analogues from methoxy-substituted benzoic acids
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The synthesis of O-desmethylangolensin (O-DMA) analogues from methoxy-substituted benzoic acids was described. Treatment of methoxy-substituted benzoic acids with 2 equiv of ethyllithium afforded methoxypropiophenones, which were subsequently transformed to ethyl 2-(methoxyphenyl)propionates via 1,2-rearrangement of the methoxyphenyl group using Pb(OAc)4/HClO4 in triethyl orthoformate. After hydrolysis with KOH, the 2-(methoxyphenyl)propionic acids were reacted with di- 2-pyridyl carbonate to afford 2-pyridyl 2-(methoxyphenyl)propionates, which were acylated with methoxy-substituted phenylmagnesium bromides to give methoxy-α-methyldesoxybenzoins. The methoxy groups of these compounds were selectively or fully demethylated using boron tribromide to give diverse O-DMA analogues in high yields.
- Hong, Hyo Jeong,Lee, Jae In
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p. 569 - 574
(2015/02/05)
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- Iron-catalyzed, highly regioselective synthesis of α-aryl carboxylic acids from styrene derivatives and CO2
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The iron-catalyzed hydrocarboxylation of aryl alkenes has been developed using a highly active bench-stable iron(II) precatalyst to give α-aryl carboxylic acids in excellent yields and with near-perfect regioselectivity. Using just 1 mol % FeCl2, bis(imino)pyridine 6 (1 mol %), CO 2 (atmospheric pressure), and a hydride source (EtMgBr, 1.2 equiv), a range of sterically and electronically differentiated aryl alkenes were transformed to the corresponding α-aryl carboxylic acids (up to 96% isolated yield). The catalyst was found to be equally active with a loading of 0.1 mol %. Preliminary mechanistic investigations show that an iron-catalyzed hydrometalation is followed by transmetalation and reaction with the electrophile (CO2).
- Greenhalgh, Mark D.,Thomas, Stephen P.
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p. 11900 - 11903
(2012/09/07)
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- Anchored Pd-complexes in mesoporous supports: Synthesis, characterization and catalysis studies for carbonylation reactions
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Pd(pyca)(PPh3)(OTs) [pyca = 2-picolinate] complex is efficiently anchored inside different mesoporous matrices, such as MCM-41, MCM-48, SBA-15 using a molecular aminopropyl tether moiety employing different synthesis strategies. Thorough characterization of the materials using powder XRD, multinuclear (13C, 29Si, 31P) CP-MAS NMR, XPS, SEM, N2-sorption studies etc. confirmed the successful anchoring of the palladium complex to the walls of the support matrices thus establishing the synthesis protocols unambiguously. The catalysts were found to be highly active and selective for the carbonylation of different aryl olefins and alcohols. Consecutive recycling and successful reuse proved the stability and true heterogeneous nature of all the anchored catalysts, which is a substantial advancement over the existing heterogeneous catalysts for carbonylation.
- Sarkar, Bibhas R.,Chaudhari, Raghunath V.
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p. 154 - 173
(2013/01/15)
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- Guanidine catalyzed aerobic reduction: A selective aerobic hydrogenation of olefins using aqueous hydrazine
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An efficient aerobic reduction of olefins, internal as well as terminal, is developed using guanidine as an organocatalyst. A remarkable chemoselectivity in reduction has been demonstrated in the presence of a variety of functional groups and protective groups and a selective reduction of a terminal olefin in the presence of an internal olefin is revealed.
- Lamani, Manjunath,Guralamata, Ravikumara Siddappa,Prabhu, Kandikere Ramaiah
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supporting information; experimental part
p. 6583 - 6585
(2012/07/14)
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- A novel synthetic route to 2-arylalkanoic acids by a ruthenium-catalyzed chemoselective oxidation of furan rings
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An efficient two-step synthesis of 2-arylalkanoic acids from 1-arylalkanols is described. Firstly, 1-arylalkylfuran derivatives were synthesized in high yields by the metal triflate catalyzed Friedel-Crafts alkylation of 2-methylfuran with 1-arylalkanols without employing anhydrous conditions. The chemoselective oxidation of the furan ring in 1-arylalkylfurans to carboxylic acid was then investigated. In a solvent system of hexane-EtOAc/H2O (1:3:4), the furan ring was selectively oxidized with 7 equivalents of NaIO 4 by using 0.5 mol% RuCl3 as catalyst to give 2-arylalkanoic acids in good yields. The selectivity of ruthenium oxidation was controlled by the solvent ratio of hexane-EtOAc. Georg Thieme Verlag Stuttgart.
- Noji, Masahiro,Sunahara, Haruka,Tsuchiya, Ken-Ichi,Mukai, Toru,Komasaka, Ayako,Ishii, Keitaro
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experimental part
p. 3835 - 3845
(2009/07/04)
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- FACTOR VIIA INHIBITOR
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The present invention relates to novel inhibitors of Factors VIIa, IXa, Xa, XIa, in particular Factor VIIa, pharmaceutical compositions comprising these inhibitors, and methods for using these inhibitors for treating or preventing thromboembolic disorders
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Page/Page column 24-25
(2010/02/15)
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- 2-Arylpropionic CXC chemokine receptor 1 (CXCR1) ligands as novel noncompetitive CXCL8 inhibitors
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The CXC chemokine CXCL8/IL-8 plays a major role in the activation and recruitment of polymorphonuclear (PMN) cells at inflammatory sites. CXCL8 activates PMNs by binding the seven-transmembrane (7-TM) G-protein-coupled receptors CXC chemokine receptor 1 (CXCR1) and CXC chemokine receptor 2 (CXCR2). (R)-Ketoprofen (1) was previously reported to be a potent and specific noncompetitive inhibitor of CXCLS-induced human PMNs chemotaxis. We report here molecular modeling studies showing a putative interaction site of 1 in the TM region of CXCR1. The binding model was confirmed by alanine scanning mutagenesis and photoaffinity labeling experiments. The molecular model driven medicinal chemistry optimization of 1 led to a new class of potent and specific inhibitors of CXCL8 biological activity. Among these, repertaxin (13) was selected as a clinical candidate drug for prevention of post-ischemia reperfusion injury.
- Allegretti, Marcello,Bertini, Riccardo,Cesta, Maria Candida,Bizzarri, Cinzia,Di Bitondo, Rosa,Di Cioccio, Vito,Galliera, Emanuela,Berdini, Valerio,Topai, Alessandra,Zampella, Giuseppe,Russo, Vincenzo,Di Bello, Nicoletta,Nano, Giuseppe,Nicolini, Luca,Locati, Massimo,Fantucci, Piercarlo,Florio, Saverio,Colotta, Francesco
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p. 4312 - 4331
(2007/10/03)
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- Synthesis of 1,4:3,6-dianhydro-d-mannitol 2,5-(hydrogenphosphate) and its usage in palladium-catalyzed hydroxycarbonylation of styrene
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Phosphorylation of 1,4:3,6-dianhydro-d-mannitol by phosphorus oxychloride in the presence of triethylamine followed by hydrolysis gave a cyclie hydrogen phosphate, which has the crystal structure of 6-hydroxy-6-oxo-2,5,7,10-tetraoxa-6-phospha-tricyclo[6.3.0.04,11]undecane. It was used as a chiral ligand in palladium-catalyzed hydroxycarbonylation of styrene. The regioselectivity was good, but the optical yield was limited.
- Jiang, Biao,Huang, Zuo-Gang,Cheng, Ke-Jun
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p. 2797 - 2803
(2007/10/03)
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- Microbial deracemization of α-substituted carboxylic acids: Substrate specificity and mechanistic investigation
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A new enzymatic method for the preparation of optically active α-substituted carboxylic acids is reported. This technique is called deracemization reaction, which provides us with a route to obtain the enantiomerically pure compounds, theoretically in 100% yield starting from the racemic mixture. This means that the synthesis of a racemate is almost equal to the synthesis of the optically active compound, and this concept is entirely different from the commonly accepted one in the asymmetric synthesis. Using the growing cell system of Nocardia diaphanozonaria JCM3208, racemates of 2-aryl- and 2-aryloxypropanoic acid are deracemized smoothly and (R)-form-enriched products are recovered in high chemical yield (>50%). In addition, using optically active starting compounds and deuterated derivatives as well as inhibitors, we have disclosed the fact that a new type of enzyme takes part in this biotransformation, and that the reaction proceeds probably via the same mechanism as that in rat liver.
- Kato, Dai-Ichiro,Mitsuda, Satoshi,Ohta, Hiromichi
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p. 7234 - 7242
(2007/10/03)
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- HPPARS ACTIVATORS
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Compounds of formula (1) or a pharmaceutically acceptable salt, solvate, acid isostere, or hydrolyzable ester thereof, are disclosed. Methods of making and using the compounds are also disclosed. In particular methods for treating diseases or conditions a
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Page/Page column 61-62
(2010/02/07)
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- An interesting synthetic application of S-alkyl (aryl)bis(alkylsulfanyl)thioacetates: General procedure for the preparation of (±)-α-arylpropionic acids
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Reported here is a new procedure for the synthesis of α-arylpropionic acids 1 in the racemic form, starting from derivatives of aromatic carboxylic acids 2 (i.e., esters), via 1-aryl-2,2,2-tris(alkylsulfanyl)ethanones 4-6, S-alkyl (aryl)bis(alkylsulfanyl)thioacetates 7-9, S-alkyl α-aryl-α-(alkylsulfanyl)thiopropionates 10-12 and S-alkyl α-arylthiopropionates 13-15. Each stage takes place easily and yields are always high.
- Clericuzio, Marco,Degani, Iacopo,Dughera, Stefano,Fochi, Rita
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p. 921 - 927
(2007/10/03)
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- Efficient transformations of aldehydes and ketones into one-carbon homologated carboxylic acids
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Peterson olefination of aldehydes and ketones with trimethylsilyl(methoxy)(benzotriazol-1-yl)methyl anion 6 afforded 1-(benzotriazol-1-yl)-1-methoxyalk-1-enes 7 which were treated without isolation with zinc bromide and hydrochloric acid, to yield the corresponding one-carbon homologated carboxylic acids 4 in good overall yields.
- Katritzky, Alan R.,Toader, Dorin,Xie, Linghong
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p. 1425 - 1427
(2007/10/03)
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- Metalation of Arylmethyl Methyl Ethers and Connection with Their Reductive Electrophilic Substitution
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Stable α-methoxy arylmethyl carbanions can be generated by metalation of arylmethyl methyl ethers, 1, with n-BuLi in THF at -40 degC, avoiding Wittig rearrengement to the corresponding alkoxides 2.Reaction of these carbanions with various electrophiles afforded the expected products 3 in satisfactory yields.Connection between the metalation procedure and the reductive electrophilic substitution of arylmethyl methyl ethers allowed the transformation of compounds 1 into 2-arylpropanoic acids, 5.
- Azzena, Ugo,Demartis, Salvatore,Fiori, Maria Giovanna,Melloni, Giovanni,Pisano, Luisa
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p. 5641 - 5644
(2007/10/02)
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- Photochemical Rearrangement of α-Chloro-Propiophenones to α-Arylpropanoic Acids: Studies on Chirality Transfer and Synthesis of (S)-(+)-Ibuprofen and (S)-(+)-Ketoprofen
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A new single-step efficient photochemical approach for α-arylpropanoic acids (4) from α-chloro-propiophenones (5) is described.It involves carbonyl triplet excited state directed 1,2-aryl migration of the aryl group which has been found to be highly dependent upon the nature of the aryl substituent.The mode of the rearrangement is probed by the study of the photobehaviour of a set of optically active α-chloro-propiophenones.The results suggest that the nature of the carbonyl triplets (n, ?*/ ?, ?*) plays an important role in the chirality transfer.This method finds application in the synthesis of optically active ibuprofen (4e) and ketoprofen (26), though in moderate optical yields.
- Sonawane, Harikisan,Bellur, Nanjundiah S.,Kulkarni, Dilip G.,Ayyangar, Nagaraj R.
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p. 1243 - 1260
(2007/10/02)
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- Presynaptic cholinergic modulators as potent cognition enhancers and analgesic drugs. 1. Tropic and 2-phenylpropionic acid esters
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Previous studies have shown that (R)-(+)-hyoscyamine has analgesic activity as a consequence of increased ACh release following antagonism of central muscarinic autoreceptors. Since the enhancement of central cholinergic transmission could be beneficial for cognitive disorders, we manipulated (R)-(+)-hyoscyamine, synthesizing several derivatives of tropic and 2-phenylpropionic acids, with the aim of obtaining drugs which are able to increase ACh release and consequently to show analgesic and nootropic activities. The results showed that several new compounds are indeed potent analgesics (with an analgesic efficacy comparable to that of morphine) and that the most potent one ((±)-19, PG9) also has remarkable cognition- enhancing properties. Our study confirmed that the mechanism of action involves ACh release even if it is still unclear whether only muscarinic autoreceptors or, also, heteroreceptors are involved.
- Gualtieri,Conti,Dei,Giovannoni,Nannucci,Romanelli,Scapecchi,Teodori,Fanfani,Ghelardini,Giotti,Bartolini
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p. 1704 - 1711
(2007/10/02)
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- Chemoenzymatic synthesis of pure enantiomeric 2-aryl propionic acids
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A new chemoenzymatic procedure to obtain pure enantiomeric 2-arylpropionic acids is described. The one pot synthesis of (±)-2-arylpropionic acids is carried out by addition of dichlorocarbene to the C=O bond of arylmethylketones and hydrogenolysis of the additon product. The racemic mixture is resolved by enantiospecific hydrolysis of the racemic ethyl esters using native lipase from Candida rugosa. The good yields, the accessibility of the starting arylmethylketones and the stereospecificity of the enzymatic hydrolysis make the process interesting in order to obtain the same non steroidal antiinflammatory drugs such as Ibuprofen or Naproxen.
- Garcia,Del Campo,Llama,Sanchez-Montero,Sinisterra
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p. 8433 - 8440
(2007/10/02)
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- Process for preparing aryl-substituted aliphatic carboxylic acids and their alkyl esters
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A new process for preparing aryl substituted aliphatic carboxylic acids or then alkyl esters is provided. A 1-aryl substituted olefin is reacted with carbon monoxide in the presence of water or an alcohol at a temperature between about 25° C. and about 200° C. An excess of several moles of water or alcohol is preferred. An acid such as hydrochloric acid may also be added. As catalyst, a mixture of a palladium compound and a copper compound with at least one acid-stable ligand are present.
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- DIRECT, REGIOSELECTIVE HYDROCARBOXYLATION OF ALKYNES TO SATURATED ACIDS BY COBALT AND NICKEL CATALYSTS UNDER PHASE TRANSFER CONDITIONS
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Phase transfer catalyzed carbonylation of alkynes in the presence of cobalt chloride, potassium cyanide, and nickel cyanide affords saturated carboxylic acids, with good selectivity observed for the branched-chain isomer.
- Lee, Jong-Tae,Alper, Howard
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p. 1769 - 1770
(2007/10/02)
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- Light-mediated direct transformation of 2-chloropropiophenones into 2-arylpropionic acids
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A strategy based on photochemical 1,2-aryl migration as the pivotal step allows efficient transformation of 2-chloro-propiophenones into 2-arylpropionic acids. A noticeable substituent-directed excited state control on the rearrangement process has been observed.
- Sonawane, Harikisan R.,Kulkarni, Dilip G.,Ayyangar, Nagaraj R.
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p. 7495 - 7496
(2007/10/02)
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- Process for the photochemical production of alpha-aryl propionic acid
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The invention resides in a novel photochemical process for the production of α-aryl propionic acids by the subjection of a solution in an organic solvent of the corresponding α-haloaryl alkyl ketones to irradiation with light having a wavelength of from 200 to 800 nm, preferably in the presence of a suitable acid scavenger for the neutralisation of any hydrohalogen acid generated during the reaction.
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- Synthesis and Properties of Some Nitroxide α-Carboxylate Salts
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Nitroxide α-carboxylates 10 and 22a-e were synthesized for evaluation as potential contrast-enhancing agents for magnetic resonance imaging applications.While pyrrolidine nitroxide carboxylate 10 was stable indefinitely, the free acid form 11 could not be
- Keana, John F. W.,Sovitj, Pou,Rosen, Gerald M.
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p. 2417 - 2420
(2007/10/02)
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- A UNIQUE 1,2-SHIFT SELECTIVITY IN 2-HYDROXYPROPIOPHENONE DIMETHYLACETALS: GENERATION OF NEW METHODOLOGIES FOR METHYL-2-ARYLPROPANOATES AND 1,2-CARBONYL TRANSPOSITION
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α-Hydroxydimethylacetals I have been shown to undergo two different rearrangements involving highly selective 1,2-shifts under mild conditions.When treated with Ph3P/CCl4 in the presence of pyridine, I were cleanly transformed via 1,2-aryl shifts into methyl 2-arylpropanoates, an important class of antiinflammatory agents; a pronounced substituent effect has been observed in this rearrangement. On the other hand, treatment of I with catalytic amount of Ph3P/I2 in benzene furnished α-methoxy-α-aryl propan-2-ones in excellent yields and culminated in the development of a new methodology for 1,2-carbonyl transposition.
- Sonawane, H. R.,Nanjundiah, B. S.,Kulkarni, D. G.,Ahuja, Jaimala R.
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p. 7319 - 7324
(2007/10/02)
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- Thallium(III) Nitrate-mediated Efficient Synthesis of 2-Arylpropionic Acids from 1-Halogenoethyl Aryl Ketones
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Treatment of 1-halogenoethyl aryl ketones (1; R = H, iBu, OMe, Me, Ph, or Br; X = Br or Cl) with Tl(NO3)3*3H2O and perchloric acid in a trialkyl orthoformate at 25-50 deg C affords alkyl esters (3) of 2-arylpropionic acid in good-to-excellent yields via 1,2-aryl migration in substrates (1).The hydrolysis of esters (3) leads to the corresponding acids, some of which are pharmaceutically important compounds.The reaction hardly occurs in methanol.The key step of the reaction is the in situ acetal formation of the starting ketone.The thallium(III) salt acts as an effective Lewis acid catalyst for both acetal formation and halide abstraction.
- Yamauchi, Takayoshi,Nakao, Kenji,Fujii, Kyoichi
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p. 1255 - 1258
(2007/10/02)
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- Studies on the Synthesis of Aphidicolin. Preparation of Aromatic Precursors for Spirocyclic Dienone Formation
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Novel syntheses of the alkanediones (12; R=Me, or CH2Ph) and the corresponding epoxides (13) are described.Attempts to cyclise these compounds to the spirocyclic dienone (4) were unsuccessful.Model studies on the phenolic keto cyano toluene-p-sulphonate (24) showed that the cyclopropane(25) was formed preferentially.A variety of related model compounds (29), (31), (32), and (37) were prepared and studied, but none could be cyclised to spirocyclic dienones.
- Bell, Vivien L.,Giddings, Peter J.,Holmes, Andrew B.,Mock, Graham A.,Raphael, Ralph A.
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p. 1515 - 1522
(2007/10/02)
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- Process for preparing alpha-arylalkanoic acids
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This invention relates to a process for preparing an alpha-arylalkanoic acid or salt thereof which comprises the rearrangement of an alpha-halo-alkylarylketal in neutral or slightly alkaline conditions, in the presence of a dipolar aprotic diluent and of a protic substance having a high dielectric constant, and the subsequent hydrolysis of the thus obtained ester.
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- Process for preparing alpha-aryl-alkanoic acids
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Alpha-alkyl-alkanoic acids are prepared by heating at boiling temperature a mixture of an alpha-halogen-alkyl-arylketone in a saturated aliphatic diol or in a mixture of saturated aliphatic diols in the presence of a Broensted's acid and by successively alkalifying the reaction mixture.
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- THE OXIDATRION OF ALDEHYDE BISULFITE ADDUCTS TO CARBOXYLIC ACIDS AND THEIR DERIVATIVES WITH DIMETHYLSULFOXIDE AND ACETIC ANHYDRIDE
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Bisulfite adducts which are readily formed from aldehydes are conveniently oxidized to carboxylic acids and derivatives by the action of DMSO/Ac2O followed by quenching with water, an alcohol or an amine.
- Wuts, Peter G. M.,Bergh, Carol L.
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p. 3995 - 3998
(2007/10/02)
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- Process for the preparation of arylalkanoic acids by oxidative rearrangement of arylalkanones
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Process for preparing an arylalkanoic acid by adding iodine to a mixture of an arylalkanone and an excess of an orthoester, heating of the mixture thus obtained, adding an inorganic base and finally an acid.
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- Process for preparing esters of aryl alkanoic acids
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Process for preparing esters of aryl alkanoic acids via oxidation of the corresponding ketones with bromine or iodine in the presence of a metal halide and an alcohol. The thus obtained esters are then easily hydrolized to give the corresponding aryl alkanoic acids which are particularly useful as anti-inflammatory, analgesic and anti-pyretic agents.
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- Process for preparing alpha-arylalkanoic acids
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Rearrangement of alpha-halo-alkylarylketals in neutral or weakly alkaline conditions and in the presence of a polar-protic medium and subsequent hydrolysis of the thus obtained esters, in the same reaction medium, to afford the corresponding alpha-arylalkanoic acids or their salts which are particularly useful as anti-inflammatory, analgesic and antipyretic agents.
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