- 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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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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- Palladium catalyzed hydrodefluorination of fluoro-(hetero)arenes
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Palladium catalyzed hydrodefluorination was developed for fine-tuning the properties of fluoro-(hetero)aromatic compounds. The robust reaction can be set up in air, requires only commercially available components, and tolerates a variety of heterocycles and functionalities relevant to drug discovery. Given the prevalence of fluorine incorporation around metabolic hotspots, the corresponding deuterodefluorination reaction may prove useful for converting fluorinated libraries to deuterated analogues to suppress the oxidative metabolism by kinetic isotope effects.
- Gair, Joseph J.,Grey, Ronald L.,Giroux, Simon,Brodney, Michael A.
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supporting information
p. 2482 - 2487
(2019/04/10)
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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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- Visible-Light-Driven External-Reductant-Free Cross-Electrophile Couplings of Tetraalkyl Ammonium Salts
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Cross-electrophile couplings between two electrophiles are powerful and economic methods to generate C-C bonds in the presence of stoichiometric external reductants. Herein, we report a novel strategy to realize the first external-reductant-free cross-electrophile coupling via visible-light photoredox catalysis. A variety of tetraalkyl ammonium salts, bearing primary, secondary, and tertiary C-N bonds, undergo selective couplings with aldehydes/ketone and CO2. Notably, the in situ generated byproduct, trimethylamine, is efficiently utilized as the electron donor. Moreover, this protocol exhibits mild reaction conditions, low catalyst loading, broad substrate scope, good functional group tolerance, and facile scalability. Mechanistic studies indicate that benzyl radicals and anions might be generated as the key intermediates via photocatalysis, providing a new direction for cross-electrophile couplings.
- Liao, Li-Li,Cao, Guang-Mei,Ye, Jian-Heng,Sun, Guo-Quan,Zhou, Wen-Jun,Gui, Yong-Yuan,Yan, Si-Shun,Shen, Guo,Yu, Da-Gang
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p. 17338 - 17342
(2019/01/04)
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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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- A Ligand-Directed Catalytic Regioselective Hydrocarboxylation of Aryl Olefins with Pd and Formic Acid
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An effective Pd-catalyzed hydrocarboxylation of aryl olefins with Ac2O and formic acid is described. A variety of 2- and 3-arylpropanoic acids can be regioselectively formed by the judicious choice of ligand without the use of toxic CO gas.
- Liu, Wei,Ren, Wenlong,Li, Jingfu,Shi, Yuan,Chang, Wenju,Shi, Yian
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supporting information
p. 1748 - 1751
(2017/04/11)
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- Nickel-Catalyzed Carboxylation of Benzylic C-N Bonds with CO2
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A user-friendly Ni-catalyzed reductive carboxylation of benzylic C-N bonds with CO2 is described. This procedure outperforms state-of-the-art techniques for the carboxylation of benzyl electrophiles by avoiding commonly observed parasitic pathways, such as homodimerization or β-hydride elimination, thus leading to new knowledge in cross-electrophile reactions.
- Moragas, Toni,Gaydou, Morgane,Martin, Ruben
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supporting information
p. 5053 - 5057
(2016/04/26)
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- Decarboxylative fluorination of aliphatic carboxylic acids via photoredox catalysis
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The direct conversion of aliphatic carboxylic acids to the corresponding alkyl fluorides has been achieved via visible light-promoted photoredox catalysis. This operationally simple, redox-neutral fluorination method is amenable to a wide variety of carboxylic acids. Photon-induced oxidation of carboxylates leads to the formation of carboxyl radicals, which upon rapid CO2-extrusion and F? transfer from a fluorinating reagent yield the desired fluoroalkanes with high efficiency. Experimental evidence indicates that an oxidative quenching pathway is operable in this broadly applicable fluorination protocol.
- Ventre, Sandrine,Petronijevic, Filip R.,Macmillan, David W. C.
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supporting information
p. 5654 - 5657
(2015/05/20)
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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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- Beyond benzyl grignards: Facile generation of benzyl carbanions from styrenes
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Benzylic functionalization is a convenient approach towards the conversion of readily available aromatic hydrocarbon feedstocks into more useful molecules. However, the formation of carbanionic benzyl species from benzyl halides or similar precursors is far from trivial. An alternative approach is the direct reaction of a styrene with a suitable coupling partner, but these reactions often involve the use of precious-metal transition-metal catalysts. Herein, we report the facile and convenient generation of reactive benzyl anionic species from styrenes. A CuI-catalyzed Markovnikov hydroboration of the styrenic double bond by using a bulky pinacol borane source is followed by treatment with KOtBu to facilitate a sterically induced cleavage of the C-B bond to produce a benzylic carbanion. Quenching this intermediate with a variety of electrophiles, including CO2, CS2, isocyanates, and isothiocyanates, promotes C-C bond formation at the benzylic carbon atom. The utility of this methodology was demonstrated in a three-step, two-pot synthesis of the nonsteroidal anti-inflammatory drug (±)-flurbiprofen. Make or break: The facile generation of benzyl anion equivalents from styrenes has been achieved by using a Cu-catalyzed hydroboration in conjunction with sterically induced cleavage of the C-B bond with tBuOK. Quenching this reactive intermediate with heteroallene electrophiles yields benzylic C-C bond formation (see scheme), and the utility of this methodology has been demonstrated by a synthesis of the nonsteroidal anti-inflammatory drug (±)-flurbiprofen. Copyright
- Grigg, R. David,Rigoli, Jared W.,Van Hoveln, Ryan,Neale, Samuel,Schomaker, Jennifer M.
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p. 9391 - 9396
(2012/08/29)
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- Highly enantioselective direct alkylation of arylacetic acids with chiral lithium amides as traceless auxiliaries
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A direct, highly enantioselective alkylation of arylacetic acids via enediolates using a readily available chiral lithium amide as a stereodirecting reagent has been developed. This approach circumvents the traditional attachment and removal of chiral auxiliaries used currently for this type of transformation. The protocol is operationally simple, and the chiral reagent is readily recoverable.
- Stivala, Craig E.,Zakarian, Armen
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supporting information; experimental part
p. 11936 - 11939
(2011/09/19)
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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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- 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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- Electrosynthesis of 2-arylpropionic acids from α-methylbenzyl chlorides and carbon dioxide by [Co(Salen)]
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The electrochemical synthesis of the 2-arylpropionic acid group of nonsteroidal anti-inflammatory agents such as ibuprofen, naproxen, indoprofen, biprofen, cicloprofen, and fenoprofen has been carried out in dimethylformamide (DMF) containing tetra-n-butylammonium perchlorate (nBu4NClO 4) by electrochemical carboxylation of α-methylbenzyl chlorides catalyzed by a schiff-base complex [Co(salen)] in an undivided cell equipped with a platinum cathode and magnesium anode under constant current density of 10 mA/cm2 in good yields. Cyclic voltammetric studies have also been carried out to investigate the mechanism by which [Co(salen)] catalyzes the cathodic reaction of α-methylbenzyl chlorides in presence of CO 2 by taking α-phenylethylchloride as the model compound. Copyright Taylor & Francis, Inc.
- Damodar,Krishna Mohan,Khaja Lateef,Jayarama Reddy
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p. 1143 - 1150
(2007/10/03)
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- Synthetic applications of o- and p-halobenzyl sulfones as zwitterionic synthons: Preparation of Ortho-substituted cinnamates and biarylacetic acids
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The synthetic applications of o-halobenzyl and p-halobenzyl sulfones as precursors of 1,3- and 1,5-zwitterionic synthons, respectively, are described. Their α-sulfonyl carbanions, generated by means of the phosphazene base P2-Et or BuLi or K2CO3 under PTC conditions, reacted with different electrophiles such as alkyl halides, aldehydes, and electrophilic olefins. Palladium-catalyzed cross-coupling processes such as Heck, Suzuki, and Sonogashira reactions can be efficiently performed at the halogen atom. These two sequential functionalization processes are applied to the synthesis of ortho-substituted cinnamates and pharmaceuticals belonging to the family of p-biarylacetic acids such as 4-biphenylacetic acid, namoxyrate, xenyhexenic acid, and biphenylpropionic acid.
- Costa, Ana,Najera, Carmen,Sansano, Jose M.
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p. 5216 - 5225
(2007/10/03)
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- Identification of novel mammalian squalene synthase inhibitors using a three-dimensional pharmacophore
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Squalene synthase (E.C. 2.5.1.21) catalyses the reductive dimerisation of farnesyl diphosphate in a [1-4] head to head fashion to form squalene, and is the first committed step in cholesterol biosynthesis. Specific inhibitors of squalene synthase would inhibit cholesterol formation and allow production of other important compounds derived from the cholesterol biosynthetic pathway, namely the ubiquinones (co-enzyme Q10), dolichol, and would also allow the isoprenylation process of ras by farnesyl-protein transferase. The construction of a hypothetical squalene synthase three-dimensional pharmacophore is presented. It serves as a template for the identification of several new potential classes of inhibitors. The synthesis, anti-microbial and mammalian pig liver squalene synthase activities of analogues based on the bicyclo[3.2.0]heptane and bicyclo[3.3.0]octane ring systems are reported. Analogues of the latter system are pro-drug type inhibitors and exhibit promising biological activity.
- Fairlamb, Ian J.S.,Dickinson, Julia M.,O'Connor, Rachael,Higson, Seamus,Grieveson, Lynsey,Marin, Veronica
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p. 2641 - 2656
(2007/10/03)
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- Structure-based design of COX-2 selectivity into flurbiprofen
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Comparative computer modeling of the X-ray crystal structures of cyclooxygenase isoforms COX-1 and COX-2 has led to the design of COX-2 selectivity into the nonselective inhibitor flurbiprofen. The COX-2 modeling was based on a postulated binding mode for flurbiprofen and took advantage of a small alcove in the COX-2 active site created by different positions of the Leu384 sidechain between COX-1 and COX-2. The design hypothesis was tested by synthesis and biological assay of a series of flurbiprofen analogs, culminating in the discovery of several inhibitors having up to 78-fold selectivity for COX-2 over COX-1.
- Bayly, Christopher I.,Black, W. Cameron,Leger, Serge,Ouimet, Nathalie,Ouellet, Marc,Percival, M. David
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p. 307 - 312
(2007/10/03)
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- Aryl acetylenes as mechanism-based inhibitors of cytochrome P450- dependent monooxygenase enzymes
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Aryl acetylenes have been investigated as inhibitors of cytochrome P450 (P450)-dependent alkoxyresorufin dealkylation activities in liver microsomes prepared from rats exposed to β-naphthoflavone, isosafrole, or phenobarbital. Many of the acetylenes investigated produce pseudo-first- order time-dependent and NADPH-dependent losses of the dealkylation activities characteristic of mechanism-based irreversible inactivation (suicide inhibition). Replacing the terminal hydrogen of aryl acetylenes with a methyl group to convert ethynes into propynes enhances the inhibition of P450 1A enzymes; in some instances, this modification converts a reversible inhibitor of P450s into a suicide inhibitor. In contrast, ethynes are more effective suicide inhibitors of P450 2B-dependent dealkylations than the corresponding propynes. Aryl acetylenes with an ethynyl group on the 2 position of naphthalene or on the 9 position of phenanthrene and arylalkyl acetylenes with alkyl chains containing 2, 3, or 4 methylene groups are selective inhibitors of P450 2B1/2B2 in liver microsomes from rats. Aryl acetylenes also act as suicide inhibitors of P450 1A2 in human liver microsomes, of purified P450 1A2 from rabbit or rat liver in reconstituted systems, and of purified recombinant human P450 1A2 and 1A1 in reconstituted systems. 4-(1-Propynyl)biphenyl (4PBi) inactivated P450 1A2-dependent ethoxyresourfin deethylation (EROD) activity in human liver microsomes in an NADPH-dependent process (k(inactivation), 0.23 min-1; K1, 2.3 μM). 4PBi also inactivated purified recombinant human P450 1A2 (k(inactivation), 0.24 min-1; K(I), 4.3 μM). In agreement with previous reports [Yun, C.-H., Hammons, G. J., Jones, G., Martin, M. V., Hopkins, N. E., Alworth, W. L., and Guengerich, F. P. (1992) Biochemistry 31, 10556-10563], 2-ethyny]naphthalene (2EN) was not a suicide inhibitor of the P450 1A2 activity in human liver microsomes but did inactivate purified human P450 1A2. Neither 4PBi nor 2EN affected diagnostic activities of human microsomal P450 2E1, 2C9/10, 3A4, or 2C19. In the systems examined, the losses of P450-dependent activity produced by these aryl acetylenes were not accompanied by corresponding decreases in the measured P450 absorption spectra. Thus P450 inactivation by these aryl acetylenes does not involve labeling and destruction of the heme. Incubation of 4PBi with microsomal P450 1A1 or 1A2 from rat liver under conditions that lead to P450-dependent enzyme inactivations generates a 2-biphenylylpropionic acid product. This suggests that the suicide inhibition of P450s by propynylaryl acetylenes proceeds via a methylaryl ketene formed by a 1,2- methyl rearrangement, analogous to the mechanism of suicide inhibition by ethynyl acetylenes that proceed via ketene intermediates formed by 1,2- hydrogen shifts [Ortiz de Montellano, P. R., and Kunze, K. L. (1981) Arch. Biochem. Biophys. 209, 710-712].
- Foroozesh, Maryam,Primrose, Ginny,Guo, Zuyu,Bell, L. Chastine,Alworth, William L.,Guengerich, F. Peter
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- Enantioselective syntheses of 2-arylpropanoic acid non-steroidal antiinflammatory drugs and related compounds
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(S)-2-[4′-(2″-Methylpropyl)phenylpropanoic acid (ibuprofen) and (S)-2-(3′-benzoylphenyl)propanoic acid (ketoprofen) have been synthesised in high enantiomeric excess. Control of stereochemistry was achieved by a combination of Sharpless epoxidalion followed by catalytic hydrogenolysis of the introduced benzylic epoxide oxygen bond. Also, the coupling of organic compounds in the presence of palladium with enantiopure 2-(3-iodophenyl)propanoic and 2-(4-iodophenyl)propanoic acids, prepared by the methodology above, is a general method for the synthesis of optically active arylpropanoic acids.
- Hamon, David P.G.,Massy-Westropp, Ralph A.,Newton, Josephine L.
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p. 12645 - 12660
(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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- Synthesis of Arylpropanoic Acids From Optically Active 2-(Iodophenyl)propanoic Acids
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The coupling of organozinc compounds with homochiral 2-(3-iodophenyl)propanoic and 2-(4-iodophenyl)propanoic acids in the presence of palladium is a general method for the synthesis of optically active arylpropanoic acids.
- Hamon, David P. G.,Massy-Westropp, Ralph A.,Newton, Josephine L.
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p. 5333 - 5336
(2007/10/02)
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- Aminoazole derivatives and their production and use
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A compound of the formula: STR1 wherein A is the group of the formula: wherein Ar1 is a phenyl or thienyl group which may be optionally substituted with at least one of the same or different halogen atom; Ar2 is a phenylene or thienylene group which may be optionally substituted with at least one of the same or different halogen atom; D is a divalent radical selected from the group consisting of >C=N--OR4 [wherein R4 is a hydrogen atom or lower alkyl group], >C=O, STR2 >CHOH, >NH radical, or single bond, STR3 wherein R5 is a lower alkoxy or a phenyl group which may be optionally substituted with at least one of the same or different halogen atom; E is a methine group or a nitrogen atom; F is a vinylene group or an oxygen atom, STR4 wherein R6 is a lower alkoxy group; R7 is a lower alkyl group; R8 is a benzoyl group which may be optionally substituted with at least one of the same or different halogen atom, B is a divalent azole group; R1 is a hydrogen atom or a lower alkyl group; R2 is a hydrogen atom, lower alkyl, aryl-lower alkyl, or the group of the formula: wherein R9 is a hydrogen atom, lower alkyl, halo-lower alkyl, amino-lower alkyl, aryl or aryl-lower alkyl group or the group of the formula: STR5 wherein R10 is a hydrogen atom or lower alkoxy group; R11 is a hydrogen atom, lower alkyl, lower alkenyl, lower cycloalkyl, aryl-lower alkyl, aryl or aroyl group; or the group of the formula: --NR10 R11 is a 5-, 6- or 7-membered saturated heterocyclic ring; or the group of the formula: wherein R12 is a lower alkyl or polyhalo-lower alkyl group; G is a divalent group selected from the group consisting of >C=O, >C=S, >(C=O)2 or >SO2 radical; or the group of the formula: --NR1 R2 is a 5-, 6- or 7-membered saturated heterocyclic ring: R3 is a hydrogen atom or lower alkyl group, or its acid addition salts, which is useful for immunomodulator.
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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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- Preparation of 2-Arylpropanoic Acids by Oxidative Aryl Migration in (β-Aryl-β-hydroxy)alkyl Phenyl Selenides
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Oxidation of diastereomeric mixtures of 1-aryl-1-hydroxyprop-2-yl phenyl selenides, prepared either by phenylselenylation of propiophenones followed by reduction or by treatment of benzaldehyde with α-(phenylseleno)ethyl anion, with an excess of meta-chloroperbenzoic acid in methanol at 25 deg C for 24 h or at reflux for 2 h affords methyl 2-arylpropanoates almost quantitatively.Similar treatment in tetrahydrofuran at 25 deg C for 24 h results in a direct formation of 2-arylpropanoic acids in high yields.
- Uemura, Sakae,Ohe, Kouichi,Yamauchi, Takayoshi,Mizutaki, Shoichi,Tamaki, Kentaro
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p. 907 - 910
(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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- Oxidative Rearrangement of Aryl Ethyl Ketones to Alkyl 2-Arylpropanoates by Lead(IV) Acetate
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Treatment of the propiophenones p-R'C6H4COCH2Me (1; R' = H, Me, Bui, Ph, Br) with lead(IV) acetate in trialkyl orthoformate in the presence of acid catalyst is found to give alkyl esters of 2-arylpropanoic acids (2) in good to excellent yields via 1,2-aryl migration in (1).Hydrolysis of (2) leads to the corresponding acids, some of which are important pharmaceutical compounds.The rate of aryl migration increases when the substituent R' is an electron-releasing group such as methyl, isobutyl, or phenyl.The rate of rearrangement of the dimethyl acetals of (1); R' = H, Bui, Ph) is nearly the same as that of (1).Such rearrangement hardly occurs in the absence of acid catalyst.A reaction pathway involving the formation of a monoalkoxylead(IV) compound, and its decomposition accompanied with aryl migration is discussed.
- Yamauchi, Takayoshi,Nakao, Kenji,Fujii, Kyoichi
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p. 1433 - 1436
(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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- Process for producing an α-aromatic group substituted alkanoic acid derivative
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Compounds having anti-inflammatory and analgesic activity of the formula STR1 are produced from compounds having the formula STR2 by rearrangement in the presence of a base or an amide and (1) X S O X 1 or X S O 2 X 1 where X and X 1 are halogen or trifluoromethyl or (2) sulfur dioxide and halogen.
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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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- Application of Oxidative Aryl Migration in Organo-selenium and -tellurium Compounds to the Synthesis of 2-Arylpropanoic Acids
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The ethylene acetals of aryl α-phenylseleno- and α-phenyltelluro-ethyl ketones i, Ph, Br) and 5-bromo-6-methoxy-2-naphthyl> have been prepared in 12-83percent yields by treating the corresponding α-bromo compounds with diphenyl diselenide-sodium or diphenyl ditelluride-sodium, respectively, in tetrahydrofuran-dimethylformamide under reflux for 6-10 h, during which the bromine is substituted by the PhSe or PhTe group.This substitution is not observed when the (PhM)2-NaBH4-EtOH (M=Se, Te) system which is known as a source of PhM- anion is used.Oxidation of the acetals thus formed with an excess of meta-chloroperbenzoic acid at 20-25 deg C for 1 h affords hydroxy-ethyl 2-arylpropanoates in 56-86percent yields via aryl group migration which are hydrolysed to 2-arylpropanoic acids, some of which are pharmaceutically important compounds.Overall isolated yields of 2-arylpropanoic acids are around 30-42percent based on the starting propiophenones over 5 steps.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Yamauchi, Takayoshi,Hattori, Kaneaki,Mizutaki, Shoichi,Tamaki, Kentaro
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p. 1983 - 1987
(2007/10/02)
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- ARENES FROM ALKANES OR CYCLOALKANES THROUGH DEHYDRATION OR REARRANGEMENT WITH PYRIDINIUM CHLORIDE
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The preparations of various kinds of arylacetic acids both from the precursors and from the synthetic equivalents of (2-oxocyclohexenyl)acetic acids are reviewed.Particular attention is paid to the methods by which these intermediates can be obtained since the usefulness of the reaction is obviously bound to substrate availability.Further developments in the field of aromatic hydrocarbons and heterocyclic compounds are illustrated and a model for the reaction is proposed.In addition to the data already published in scientific journals and in the patent literature, several unpublished data are reported.
- Baiocchi, Leandro,Giannangeli, Marilena,Bonanomi, Michele,Picconi, Giuseppe,Ridolfi, Pietro
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p. 199 - 216
(2007/10/02)
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- New Preparative Method for 2-Arylpropanoic Acids by Oxidative Aryl Migration in Aryl α-Seleno- and Aryl α-Telluro-ethyl Ketones
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Oxidation with m-chloroperbenzoic acid of the ethylene acetals of aryl α-phenylseleno- or aryl α-phenyltelluro-ethyl ketones prepared by treating the corresponding α-bromo compounds with diphenyl diselenide-sodium or diphenyl ditelluride-sodium, respectively, affords hydroxyethyl 2-arylpropanoates in moderate to good yields via aryl group migration.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Yamauchi, Takayoshi,Hattori, Kaneaki,Mizutaki, Shoichi,Tamaki, Kentaro
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p. 426 - 427
(2007/10/02)
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- Process for preparing α-substituted phenylalkanecarboxylic acid
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A process for preparing an α-substituted phenylalkanecarboxylic acid, having useful pharmaceutical properties such as analgesic, anti-inflammatory and anti-pyretic properties, from the corresponding ethylidenecyanoacetate by oxidation, hydrolysis, decarboxylation and oxidation.
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