- Asymmetric Aminations and Kinetic Resolution of Acyclic α-Branched Ynones
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An efficient method for asymmetric synthesis of acyclic α-tertiary amine derivatives has been achieved through enantioselective aminations of α-branched ynones with azodicarboxylates enabled by chiral phosphoric acid catalysis. Moreover, kinetic resolution of racemic starting material was realized under these conditions, which gave access to valuable enantioenriched α-substituted ketones. A wide array of α-aryl and alkyl-substitutions, and the substituted alkynyl groups were well compatible with this method, producing both the amination products and the recovered ketones with good to high enantioselectivities.
- He, Faqian,Shen, Guosong,Yang, Xiaoyu
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supporting information
p. 15 - 20
(2021/11/20)
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- syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
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Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
- Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
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supporting information
p. 3604 - 3612
(2021/07/26)
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- Palladium-Catalyzed Asymmetric Markovnikov Hydroxycarbonylation and Hydroalkoxycarbonylation of Vinyl Arenes: Synthesis of 2-Arylpropanoic Acids
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Asymmetric hydroxycarbonylation is one of the most fundamental yet challenging methods for the synthesis of carboxylic acids. Herein, we reported the development of a palladium-catalyzed highly enantioselective Markovnikov hydroxycarbonylation of vinyl arenes with CO and water. A monodentate phosphoramidite ligand L6 plays vital role in the reaction. The reaction tolerates a range of functional groups, and provides a facile and atom-economical approach to an array of 2-arylpropanoic acids including several commonly used non-steroidal anti-inflammatory drugs. The catalytic system has also enabled an asymmetric Markovnikov hydroalkoxycarbonylation of vinyl arenes with alcohols to afford 2-arylpropanates. Mechanistic investigations suggested that the hydropalladation is irreversible and is the regio- and enantiodetermining step, while hydrolysis/alcoholysis is probably the rate-limiting step.
- Guan, Zheng-Hui,Ren, Zhi-Hui,Wang, Yuan,Yang, Hui-Yi,Yao, Ya-Hong,Zou, Xian-Jin
-
supporting information
p. 23117 - 23122
(2021/09/18)
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- Efficient palladium-catalyzed synthesis of 2-aryl propionic acids
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A flexible two-step, one-pot procedure was developed to synthesize 2-aryl propionic acids including the anti-inflammatory drugs naproxen and flurbiprofen. Optimal results were obtained in the presence of the novel ligand neoisopinocampheyldiphenylphosphine (NISPCPP) (9) which enabled the efficient sequential palladium-catalyzed Heck coupling of aryl bromides with ethylene and hydroxycarbonylation of the resulting styrenes to 2-aryl propionic acids. This cascade transformation leads with high regioselectivity to the desired products in good yields and avoids the need for additional purification steps.
- Neumann, Helfried,Sergeev, Alexey G.,Spannenberg, Anke,Beller, Matthias
-
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- Palladium-Catalyzed Alkoxycarbonylation of sec-Benzylic Ethers
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Herein, we report the palladium-catalyzed synthesis of 3-arylpropionate esters starting from secondary benzylic ethers. With this investigation it could be shown that ethers are suitable starting materials in addition to the established carbonylation reactions of olefins, alcohols, or aryl halides.
- Beller, Matthias,Jackstell, Ralf,Maes, Bert U. W.,Schneider, Carolin
-
supporting information
(2020/02/25)
-
- A general platinum-catalyzed alkoxycarbonylation of olefins
-
Hydroxy- and alkoxycarbonylation reactions constitute important industrial processes in homogeneous catalysis. Nowadays, palladium complexes constitute state-of-the-art catalysts for these transformations. Herein, we report the first efficient platinum-catalysed alkoxycarbonylations of olefins including sterically hindered and functionalized ones. This atom-efficient catalytic transformation provides straightforward access to a variety of valuable esters in good to excellent yields and often with high selectivities. In kinetic experiments the activities of Pd- and Pt-based catalysts were compared. Even at low catalyst loading, Pt shows high catalytic activity.
- Beller, Matthias,Dühren, Ricarda,Franke, Robert,Ge, Yao,Huang, Weiheng,Jackstell, Ralf,Liu, Jiawang,Neumann, Helfried,Schneider, Carolin,Yang, Ji
-
supporting information
p. 5235 - 5238
(2020/07/30)
-
- PYRAZOLOTRIAZOLOPYRIMIDINE DERIVATIVES AS A2A RECEPTOR ANTAGONIST
-
Disclosed herein is a pyrazolotriazolopyrimidine derivative or a stereoisomer thereof, or a pharmaceutically acceptable salt thereof useful as an A2A receptor antagonist, and a pharmaceutical composition comprising the same. Also disclosed herein is a method of treating cancer using the pyrazolotriazolopyrimidine derivative or a stereoisomer thereof, or a pharmaceutically acceptable salt thereof as an A2A receptor antagonist.
- -
-
Paragraph 0423; 0425
(2019/11/04)
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- Iridium-Catalyzed α-Methylation of α-Aryl Esters Using Methanol as the C1 Source
-
IrCl(cod)2]/dppe-catalyzed α-methylation of aryl esters using methanol as the C1 source was developed. This methylation process is useful in several fields including organic chemistry, biochemistry, and medicinal chemistry. Readily available methanol as methylation reagent was successfully adapted. The reaction processed high atom economy and efficient. By applying the reaction system, the synthesis method of naproxen was provided.
- Tsukamoto, Yuya,Itoh, Satoshi,Kobayashi, Masaki,Obora, Yasushi
-
supporting information
p. 3299 - 3303
(2019/05/10)
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- Ni-Catalyzed Reductive C-O Bond Arylation of Oxalates Derived from α-Hydroxy Esters with Aryl Halides
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A Ni-catalyzed reductive cross-coupling of α-hydroxycarbonyl compounds modified with oxalyl groups and aryl halides has been developed that furnishes α-aryl esters under mild conditions and tolerates a variety of functionalized aryl halides bearing electron-withdrawing and -donating groups. This work highlights C-O bond fragmentation on secondary alkyl carbon centers that generates α-carbonyl radicals.
- Gao, Mengyu,Sun, Deli,Gong, Hegui
-
supporting information
p. 1645 - 1648
(2019/03/11)
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- Stereodivergent coupling of aldehydes and alkynes via synergistic catalysis using Rh and Jacobsen's amine
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We report an enantioselective coupling between α-branched aldehydes and alkynes to generate vicinal quaternary and tertiary carbon stereocenters. The choice of Rh and organocatalyst combination allows for access to all possible stereoisomers with high enantio-, diastereo-, and regioselectivity. Our study highlights the power of catalysis to activate two common functional groups and provide access to divergent stereoisomers and constitutional structures.
- Cruz, Faben A.,Dong, Vy M.
-
supporting information
p. 1029 - 1032
(2017/05/15)
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- Stereodivergent Coupling of Aldehydes and Alkynes via Synergistic Catalysis Using Rh and Jacobsen's Amine
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We report an enantioselective coupling between α-branched aldehydes and alkynes to generate vicinal quaternary and tertiary carbon stereocenters. The choice of Rh and organocatalyst combination allows for access to all possible stereoisomers with high ena
- Cruz, Faben A.,Dong, Vy M.
-
supporting information
p. 1029 - 1032
(2021/09/04)
-
- Palladium-Catalyzed Carbonylation of sec- and tert-Alcohols
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A general palladium-catalyzed synthesis of linear esters directly from sec- and tert-alcohols is described. Compared to the classic Koch–Haaf reaction, which leads to branched products, this new transformation gives the corresponding linear esters in high yields and selectivity. Key for this protocol is the use of an advanced palladium catalyst system with L2 (pytbpx) as the ligand. A variety of aliphatic and benzylic alcohols can be directly used and the catalyst efficiency for the benchmark reaction is outstanding (turnover number up to 89 000).
- Dong, Kaiwu,Sang, Rui,Liu, Jie,Razzaq, Rauf,Franke, Robert,Jackstell, Ralf,Beller, Matthias
-
supporting information
p. 6203 - 6207
(2017/05/22)
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- Stereoselective Ketone Rearrangements with Hypervalent Iodine Reagents
-
The first stereoselective version of an iodine(III)-mediated rearrangement of arylketones in the presence of orthoesters is described. The reaction products, α-arylated esters, are very useful intermediates in the synthesis of bioactive compounds such as ibuprofen. With chiral lactic acid-based iodine(III) reagents product selectivities of up to 73 % ee have been achieved.
- Malmedy, Florence,Wirth, Thomas
-
supporting information
p. 16072 - 16077
(2016/10/30)
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- A recyclable CO surrogate in regioselective alkoxycarbonylation of alkenes: Indirect use of carbon dioxide
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Herein, we report a Pd-catalysed alkoxycarbonylation of alkenes based on the use of a recyclable CO2 reduction product, the crystalline and air-stable N-formylsaccharin, as a CO surrogate. The carbonylation proceeds under ambient conditions in an exceptionally complementary regioselective fashion yielding the desired branched products from styrene derivatives and valuable linear esters from alkyl-substituted alkenes.
- Gehrtz,Hirschbeck,Fleischer
-
supporting information
p. 12574 - 12577
(2015/08/06)
-
- Various oxidative reactions with novel ion-supported (diacetoxyiodo) benzenes
-
The oxidation of secondary alcohols and primary alcohols with two novel ion-supported (diacetoxyiodo)benzenes (IS-DIBs) A and B in the presence of a catalytic amount of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) in dichloromethane at room temperature proceeded efficiently to provide the corresponding ketones and aldehydes, respectively, in good yields. The oxidative reaction of N,N-diisopropylbenzylamines with those IS-DIBs was also carried out to generate the corresponding aromatic aldehydes in good yields. In addition, the Hofmann rearrangement of primary amides in methanol under basic conditions and the oxidative 1,2-rearrangement of propiophenones in trimethyl orthoformate under acidic conditions with those IS-DIBs provided the corresponding methyl carbamates and methyl 2-arylpropanoates, respectively, in good yields. Moreover, treatment of acetophenones with those IS-DIBs in the presence of trifluoromethanesulfonic acid in acetonitrile generated the corresponding 5-aryl-2-methyloxazoles in good yields. In those five reactions, the desired products were obtained in good yields with high purity by simple extraction of the reaction mixture with diethyl ether and subsequent removal of the solvent from the extract. Moreover, ion-supported iodobenzenes, which were the co-products derived from IS-DIBs in the present oxidative reactions, were recovered in good yields and could be re-oxidized to IS-DIBs A and B for reuse in the same oxidative reactions.
- Iinuma, Masataka,Moriyama, Katsuhiko,Togo, Hideo
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p. 2961 - 2970
(2013/04/10)
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- Nickel-catalyzed reductive hydroesterification of styrenes using CO 2 and MeOH
-
Complexes [(dippe)Ni(μ-H)]2 (A) (dippe = 1,2-bis-di- isopropylphosphino)ethane) and [(dtbpe)Ni(μ-H)]2 (B) (dtbpe = 1,2-bis-di-tert-butylphospino)ethane) catalyze the reductive hydroesterification of styrenes with the use of CO2 and MeOH. The latter acts as a hydrogen source and as an esterificating agent, to yield the corresponding branched and linear esters in moderate to good yields. In all of the studied reactions the linear esters were obtained in higher amounts than the branched ones. When the hydroesterification reaction was carried out using a stoichiometric metal/substrate ratio, the complexes [(P-P)Ni(CO)2] and [(P-P)Ni(CO3)] (P-P = dippe or dtbpe) were isolated and characterized by standard spectroscopic methods. Compounds [(dtbpe)Ni(CO) 2] and [(dtbpe)Ni(CO3)] were also fully characterized by single-crystal X-ray diffraction.
- Gonzalez-Sebastian, Lucero,Flores-Alamo, Marcos,Garcia, Juventino J.
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p. 8200 - 8207
(2013/02/22)
-
- Enantioselective hydrogenation of α-substituted acrylic acids catalyzed by iridium complexes with chiral spiro aminophosphine ligands
-
Highly active: Iridium complexes with chiral spiro aminophosphine ligands were synthesized and applied as catalysts for the asymmetric hydrogenation of α-substituted acrylic acids (see scheme). The complexes were highly active catalysts, showing turnover frequencies of up to 6000 h-1, and catalyst loadings could be reduced to 0.01 mol %. Copyright
- Zhu, Shou-Fei,Yu, Yan-Bo,Li, Shen,Wang, Li-Xin,Zhou, Qi-Lin
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p. 8872 - 8875
(2012/10/08)
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- Pd/Josiphos-catalyzed enantioselective α-arylation of silyl ketene acetals and mechanistic studies on transmetalation and enantioselection
-
Palladium/(4-MeO-3,5-MePh)2PF-Pcy2) catalyzed the enantioselective arylation of silyl ketene acetals with iodoarenes in the presence of TlOAc to promote transmetalation of silyl ketene acetals. The highest enantioselectivities giving α-arylesters up to 91% ee were achieved when (E)-1-methoxy-1-(trimethylsiloxy)propene (E/Z = 88/12) was used for the silyl ketene acetal. The effect on enantioselection of a chiral ligand is discussed on the basis of the X-ray structure of the palladium/(4-MeO-3,5- MePh)2PF-Pcy2) complex and results of DFT computational studies on mechanistic aspects of the catalytic cycle.
- Kobayashi, Kenya,Yamamoto, Yasunori,Miyaura, Norio
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scheme or table
p. 6323 - 6327
(2012/01/31)
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- A novel synthetic route to 2-arylalkanoic acids by a ruthenium-catalyzed chemoselective oxidation of furan rings
-
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
-
experimental part
p. 3835 - 3845
(2009/07/04)
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- Oxidative rearrangements of arylalkanones with 1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide, a 'green' analog of Koser's reagent
-
Previous methods for the conversion of arylalkanones to alkyl 2-arylesters by oxidative rearrangement utilized reagents which either produced toxic metal salts or halogenated organics as by-products. In this report, 1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide (HMBI) is used to effect this useful transformation, where the reduced iodine reagent is water-soluble and readily recycled.
- Justik, Michael W.
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p. 3003 - 3007
(2008/02/06)
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- Ni-catalyzed activation of α-chloroesters: a simple method for the synthesis of α-arylesters and β-hydroxyesters
-
Coupling reactions of α-chloroesters with aryl halides (α-arylation) or carbonyl compounds (Reformatsky) using nickel catalyst allow, under mild conditions, the preparation of various functionalized aryl propionic acid derivatives or β-hydroxyesters. In the synthesis of aryl propionic acid derivatives, the process is efficient with aryl halides bearing either electron-withdrawing or electron-donating groups.
- Durandetti, Muriel,Gosmini, Corinne,Périchon, Jacques
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p. 1146 - 1153
(2007/10/03)
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- Asymmetric intermodular heck-type reaction of acyclic alkenes via oxidative palladium(II) catalysis
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Herein, we report an asymmetric intermolecular Heck-type reaction of acyclic alkenes by using a palladium-pyridinyl oxazoline diacetate complex under oxidative palladium(II) catalysis conditions. A premade palladium-ligand complex afforded higher enantioselectivities than a corresponding premixed palladium-ligand system, while offering enhanced asymmetric induction when compared to known intermolecular Heck-type protocols.
- Yoo, Kyung Soo,Park, Chan Pil,Yoon, Cheol Hwan,Sakaguchi, Satoshi,O'Neill, Justin,Jung, Kyung Woon
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p. 3933 - 3935
(2008/02/11)
-
- Biphenyl- and terphenyl-based recyclable organic trivalent iodine reagents
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Biphenyl- and terphenyl-based recyclable trivalent iodine reagents, such as 4-bromo-4′-(diacetoxyiodo)biphenyl, 4,4′-bis(diacetoxyiodo)biphenyl, 1,4-bis[4-(diacetoxyiodo)phenyl]benzene, 4-bromo-4′-[(hydroxy)(tosyloxy)iodo]biphenyl, 4,4′-bis[(hydroxy)(tosyloxy)iodo]biphenyl, were simply prepared and their reactivities for the oxidative rearrangement of ketones to esters, TEMPO-mediated oxidation of alcohols to aldehydes or ketones, oxidative dealkylation of N-alkylsulfonamides to sulfonamides, and α-tosyloxylation of ketones were compared with p-(diacetoxyiodo)toluene and p-[(hydroxy)(tosyloxy)iodo]toluene to show the same reactivities and, moreover, the biphenyl- and terphenyl-based iodoarenes formed were recovered by simple filtration of the reaction mixture in every reaction. Thus, these biphenyl- and terphenyl-based trivalent iodine reagents can be used as the recyclable reagents.
- Moroda, Atsushi,Togo, Hideo
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p. 12408 - 12414
(2007/10/03)
-
- 2-Arylpropionic CXC chemokine receptor 1 (CXCR1) ligands as novel noncompetitive CXCL8 inhibitors
-
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
-
p. 4312 - 4331
(2007/10/03)
-
- Microbial deracemization of α-substituted carboxylic acids: Substrate specificity and mechanistic investigation
-
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)
-
- Isothiazole derivatives and their use as pesticides
-
A compound of formula (I), where A is optionally substituted alkylene, alkenylene, alkynylene, cycloalkylene, alkylenoxy, oxy(C1-6)alkylene, alkylenethio, thio(C1-6)alkylene, C1-6alkylenamino, amino(C1-6)alkylene, [C1-6alkyleneoxy(C1-6)alkylene], [C1-6alkylenethio(c1-6)alkylene], [1-6alkylenesulfinyl(c1-6)alkylene], [c1-6alkylenesulfonyl(C1-6)alkylenc] or [C1-6alkyleneamino(C1-6)alkylene]; provided that A is not CH2 or CH2O; B is N, N-oxide or CR8; Y is O, S or NR9; Z is O, S or NR10; and R1, R2, R3, R4, R5, R6, R7, R8, R9, R10 are specified radicals; compositions containing them; processes for making them; and their use as insecticides or fungicides.
- -
-
Page/Page column 39
(2010/11/29)
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- Total synthesis of sporochnols, fish deterrents from a marine alga
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Sporochnols, fish deterrents from a marine alga, were synthesized, using intramolecular C-H insertion of alkylidenecarbene as a key step to construct the chiral quaternary center.
- Ohira, Susumu,Kuboki, Atsuhito,Hasegawa, Taisuke,Kikuchi, Takato,Kutsukake, Tatsuhiko,Nomura, Maki
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p. 4641 - 4644
(2007/10/03)
-
- A novel approach to the synthesis of 2-aryl propionates
-
A two step conversion of phenyl glyoxylates to 2-aryl-propionates has been accomplished. Esters of phenylglyoxylic acid have been converted to corresponding β,β-dichlorostyrenes. These on further reduction gave esters of 2-arylpropionic acids.
- Patil,Wadia
-
p. 2821 - 2827
(2007/10/03)
-
- Synthetic use of poly[4-(diacetoxyiodo)styrene] for organic reactions
-
Poly[4-(diacetoxyiodo)styrene] is sufficiently reactive for the iodination of aromatics, the oxidative 1,2-aryl migration of alkyl aryl ketones, the α-hydroxylation of ketones, and the oxidation of hydroquinones and sulfides similarly to (diacetoxyiodo)benzene. Here, those reactions with poly[4-(diacetoxyiodo)styrene] are very useful because of the simple operation; thus, filtration gives the crude products and recovered poly(4- iodostyrene), and then poly[4-(diacetoxyiodo)-styrene] can be regenerated by oxidation of the recovered poly(4-iodostyrene), which are reused for the same reactions.
- Togo, Hideo,Abe, Seiichiro,Nogami, Genki,Yokohama, Masataka
-
p. 2351 - 2356
(2007/10/03)
-
- Nickel-catalyzed direct electrochemical cross-coupling between aryl halides and activated alkyl halides
-
The electrochemical reduction of a mixture of aryl halides and activated alkyl halides in DMF in the presence of catalytic amount of NiBr2bipy leads to cross-coupling products in good to high yields. The method applies to the synthesis of α-aryl ketones, α-aryl esters, and allylated compounds from readily available organic halides. Optimization of the process has been obtained by slowly adding the most reactive organic halide (usually the activated alkyl halide) during the electrolysis which is best conducted at 70 °C when aryl bromides are involved.
- Durandetti, Muriel,Nedelec, Jean-Yves,Perichon, Jacques
-
p. 1748 - 1755
(2007/10/03)
-
- Photochemical Rearrangement of α-Chloro-Propiophenones to α-Arylpropanoic Acids: Studies on Chirality Transfer and Synthesis of (S)-(+)-Ibuprofen and (S)-(+)-Ketoprofen
-
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)
-
- Enzyme catalyzed monohydrolysis of 2-aryl-1 3-propanediol diacetates. A study of structural effects of the aryl moiety on the enantioselectivity
-
PPL catalyzed monohydrolysis of 2-aryl substituted 13-propanediol diacetates afforded the corresponding monoacetates in acceptable to fair chemical and optical yields. Electronic effects in the aromatic ring were examined. Elaboration of some 2-arylpropanediol monoacetates to optically active 2-arylpropanols and propanoic acids was performed.
- Guanti, Giuseppe,Narisano, Enrica,Podgorski, Tadeusz,Thea, Sergio,Williams, Andrew
-
p. 7081 - 7092
(2007/10/02)
-
- Diethylaminosulphur Trifluoride (DAST) as an Effective Reagent for Preparation of Methyl 2-Arylpropanoates from 1-Aryl-1,1-dimethoxypropan-2-ols
-
Treatment of dimethylacetals of aryl 1-hydroxyethyl ketones (Ar= Ph, 4-PhC6H4, 4-BuiC6H4, 4-MeOC6H4, 4-BrC6H4, 6-MeOnaphthalen-2-yl) with diethylaminosulphur trifluoride (DAST) affords smoothly the methyl 2-arylpropanoates in good yield via aryl-group migration.On the other hand, treatment of aryl 1-hydroxyethyl ketones with DAST gives the corresponding aryl 1-fluoroethyl ketones (Ar= Ph, 4-PhC6H4, 4-BuiC6H4) in high yield.
- Yamauchi, Takayoshi,Hattori, Kaneaki,Ikeda, Shun-ichi,Tamaki, Kentaro
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p. 1683 - 1685
(2007/10/02)
-
- Nickel-catalysed Electroreductive Coupling of α-Halogenoesters with Aryl or Vinyl Halides
-
β,γ-Unsaturated esters are obtained in moderate to good yields by a one-step electrochemical procedure from α-chloroesters and aryl or vinyl halides; a sacrificial aluminium anode, dimethylformamide as solvent, and a catalytic amount of nickel bromide-2,2'-bipyridine complex are used.
- Conan, Annie,Sibille, Soline,d'Incan, Esther,Perichon, Jacques
-
-
- ENZYMATIC RESOLUTION OF METHYL 2-ALKYL-2-ARYLACETATES
-
Horse liver esterase, used as its inexpensive commercial acetone powder, catalyzes the selective hydrolysis of methy 2-alkyl-2-arylacetates to afford R(-)-2-alkyl-2-arylacetic acids and S(+)-methyl 2-alkyl-2-arylacetates.
- Ahmar, M.,Girard, C.,Bloch, R.
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p. 7053 - 7056
(2007/10/02)
-
- A UNIQUE 1,2-SHIFT SELECTIVITY IN 2-HYDROXYPROPIOPHENONE DIMETHYLACETALS: GENERATION OF NEW METHODOLOGIES FOR METHYL-2-ARYLPROPANOATES AND 1,2-CARBONYL TRANSPOSITION
-
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)
-
- 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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- Preparation of Methyl 2-Arylpropanoates by the Reaction of 2-Hydroxypropiophenone Dimethyl Acetals with Sulfuryl Chloride in the Presence of an Amide or a Weak Base
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Treatment of 2-hydroxypropiophenone dimethyl acetals (1; R=H, i-Bu, OMe, Ph, Br) with sulfuryl chloride in the presence of an amide or a weak base affords methyl 2-arylpropanoates (2) in good to excellent yields via 1,2-aryl migration of 1.The hydrolysis of 2 leads to the corresponding acids some of which are pharmaceutically important compounds having nonsteroidal anti-inflammatory and analgesic acivities.The aryl migration proceeds stereospecifically with complete inversion of configuration at the β-carbon atom.
- Yamauchi, Takayoshi,Hattori, Kaneaki,Nakao, Kenji,Tamaki, Kentaro
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p. 4015 - 4018
(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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- 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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- A Lewis Acid Catalyzed 1,2 Aryl Shift in α-Haloalkyl Aryl Acetals: A Convenient Route to α-Arylalkanoic Acids
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A new method for the synthesis of α-arylalkanoic acids is given, based on Lewis acid promoted rearrangement of acetals of primary and secondary α-haloalkyl aryl ketones (halo = Br, Cl) in hydrocarbon solvents.The reaction is selective, providing the esters of α-arylalkanoic acids in almost quantitative yields.The ability of "soft and borderline" Lewis acids in activating the carbon-halogen bond is compared with that of silver salts.The reaction mechanism is discussed.The present synthesis has been applied to some α-arylpropionic acids well-known as antiinflammatory drugs.
- Castaldi, Graziano,Belli, Aldo,Uggeri, Fulvio,Giordano, Claudio
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p. 4658 - 4661
(2007/10/02)
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