- Organocatalytic, Organic Oxidant Promoted, Enamine C?H Oxidation/Cyclopropanation Reaction
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Herein, we demonstrate that organic, single-electron oxidant in the presence of diarylprolinol silylether type catalyst serves as a tool for the transformation of electron-rich enamines to iminium ions. These iminium ions take part in a subsequent Michael-initiated ring-closure (MIRC) reaction with in situ present nucleophile giving rise to overall cyclopropanation reaction of saturated aldehydes. Stereodefined cyclopropanes are obtained in high yields and selectivities. This one-pot transformation represents the additional example of saturated aldehydes being used in the coupled one-pot processes. (Figure presented.).
- Bond?i?, Aleksandra M.,Bond?i?, Bojan P.,D?ambaski, Zdravko,Kokotos, Christoforos G.,Triandafillidi, Ierasia
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supporting information
p. 4002 - 4008
(2021/07/06)
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- Stereodivergent Nucleophilic Additions to Racemic β-Oxo Acid Derivatives: Fast Addition Outcompetes Stereoconvergence in the Archetypal Configurationally Unstable Electrophile
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Additions of carbon nucleophiles to racemic α-stereogenic β-oxo acid derivatives that deliver enantiomerically enriched tertiary alcohols are valuable, but uncommon. This article describes stereodivergent Cu-catalyzed borylative cyclizations of racemic β-oxo acid derivatives bearing tethered pro-nucleophilic olefins to deliver highly functionalized cyclopentanols containing four contiguous stereogenic centers. The reported protocol is applicable to a range of β-oxo acid derivatives, and the diastereomeric products are readily isolable by typical chromatographic techniques. α-Stereogenic-β-keto esters are typically thought to have extreme or spontaneous configurational fragility, but mechanistic studies for this system reveal an unusual scenario wherein productive catalysis occurs on the same time scale as background substrate racemization and completely outcompetes on-cycle epimerization, even under the basic conditions of the reaction.
- Crawford, Evan T.,De Jesús Cruz, Pedro,Johnson, Jeffrey S.,Liu, Shubin
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p. 16264 - 16273
(2021/10/21)
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- Synthesis of Antitricyclic Morpholine Derivatives through Iodine(III)-Mediated Intramolecular Umpolung Cycloaddition of Olefins
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A (diacetoxyiodo)benzene-mediated intramolecular cycloaddition of olefins to construct tricyclic morpholines is presented. A series of substituted tricyclic morpholines were obtained in one-step simple operation under mild conditions, and the NMR studies
- Deng, Qingfu,Feng, Yangyang,Xiong, Ruimei,Xiong, Yan,Yang, Chenglin,Zhang, Xiaohui
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p. 4500 - 4506
(2020/04/09)
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- Bidentate auxiliary-directed alkenyl C-H allylation: Via exo-palladacycles: Synthesis of branched 1,4-dienes
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An alkenyl C-H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-Alkenes and allyl carbonates. With the use of an 8-Aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-Assisted C-H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative scale, selective conversion of inseparable Z/E alkenes and ready removal of the amide auxiliary to provide the corresponding ester.
- Shen, Cong,Lu, Xiunan,Zhang, Jian,Ding, Liyuan,Sun, Yaling,Zhong, Guofu
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supporting information
p. 13582 - 13585
(2019/11/14)
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- Enantioselective Organocatalytic Enamine C?H Oxidation/Diels- Alder Reaction
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α,β-unsaturated aldehydes have been traditionally used in LUMO lowering asymmetric aminocatalysis (iminium catalysis), while the use of saturated aldehydes as substrates in this type of catalysis has been elusive, until recently. Herein, we demonstrate that organic, single-electron oxidants in the presence of diarylprolinol silylether type catalysts serve as effective tools for the transformation of electron rich enamines to iminium ions which partake in a subsequent Diels-Alder reaction. This enantioselective one-pot transformation represents the first example of saturated aldehydes being used in domino Diels-Alder reaction processes and demonstrates the power of this protocol for construction of stereo-defined chiral compounds and building blocks. (Figure presented.).
- D?ambaski, Zdravko,Tzaras, Dimitrios-Ioannis,Lee, Sunggi,Kokotos, Christoforos G.,Bondzic, Bojan P.
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supporting information
p. 1792 - 1797
(2019/02/25)
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- Synthetic and Computational Study of Tin-Free Reductive Tandem Cyclizations of Neutral Aminyl Radicals
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5-exo, 5-exo Cyclizations of conformationally unbiased propargylic aminyl radicals proceed with excellent yield, chemoselectivity, and diastereoselectivity under tin-free reductive cyclization conditions, regardless of the electronic environments and intermediate radical stabilization resulting from various olefin substituents. These conditions avoid the need for slow addition of initiator and reductant. By contrast, analogous 6-exo, 5-exo cyclizations require substituents capable of intermediate radical stabilization to avoid premature reduction products. These experimental results are corroborated by computations that further establish the reactivity of these aminyl radicals upon exposure to tin-free cyclization conditions.
- Sirinimal, Hansamali S.,Hebert, Sebastien P.,Samala, Ganesh,Chen, Heng,Rosenhauer, Gregory J.,Bernhard Schlegel,Stockdill, Jennifer L.
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supporting information
p. 6340 - 6344
(2018/10/09)
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- Rapid Access to Thiolactone Derivatives through Radical-Mediated Acyl Thiol-Ene and Acyl Thiol-Yne Cyclization
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A new synthetic approach to thiolactones that employs an efficient acyl thiol-ene (ATE) or acyl thiol-yne (ATY) cyclization to convert unsaturated thiocarboxylic acid derivatives into thiolactones under very mild conditions is described. The high overall yields, fast kinetics, high diastereoselectivity, excellent regiocontrol, and broad substrate scope of these reaction processes render this a very useful approach for diversity-oriented synthesis and drug discovery efforts. A detailed computational rationale is provided for the observed regiocontrol.
- McCourt, Ruairi O.,Dénès, Fabrice,Sanchez-Sanz, Goar,Scanlan, Eoin M.
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p. 2948 - 2951
(2018/05/28)
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- trans-Cyclooctenes as Halolactonization Catalysts
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The strained olefins in trans-cyclooctenes serve as efficient catalysts for halolactonizations, including bromolactonizations and iodolactonizations. The trans-cyclooctene framework is essential for excellent catalytic performance, and the substituents also play important roles in determining efficiency. These results are the first demonstration of catalysis by a trans-cyclooctene.
- Einaru, Shunsuke,Shitamichi, Kenta,Nagano, Tagui,Matsumoto, Akira,Asano, Keisuke,Matsubara, Seijiro
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p. 13863 - 13867
(2018/09/27)
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- Iridium-Catalyzed Aerobic α,β-Dehydrogenation of γ,δ-Unsaturated Amides and Acids: Activation of Both α- And β-C-H bonds through an Allyl-Iridium Intermediate
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Direct aerobic α,β-dehydrogenation of γ, δ-unsaturated amides and acids using a simple iridium/copper relay catalysis system is described. We developed a new strategy that overcomes the challenging issue associated with the low α-acidity of amides and acids. Instead of α-C-H metalation, this reaction proceeds by β-C-H activation, which results in enhanced α-acidity. Conjugated dienamides and dienoic acids were synthesized in excellent yield with this reaction, which uses a simple reaction protocol. Mechanistic experiments suggest a catalyst resting state mechanism in which both α-C-H and β-C-H cleavage is accelerated.
- Wang, Zhen,He, Zhiqi,Zhang, Linrui,Huang, Yong
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supporting information
p. 735 - 740
(2018/01/26)
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- Aminolithiation–arylation consecutive cyclization of N-(2-fluorophenyl)methylaminoalkylstyryls giving aryl-substituted pyrido[1,2-b]isoquinolines
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Aminolithiation–arylation tandem cyclization of N-(2-fluorophenyl)methylaminoalkylstyryls proceeded smoothly to give hexahydro-2H-pyrido[1,2-b]isoquinoline using a stoichiometric amount of n-BuLi with high trans selectivity. The arylation reaction was highly accelerated by the addition of HMPA. Both pyrido- and pyrrolo-[1,2-b]isoquinoline were successfully constructed by this tandem reaction.
- Yamamoto, Yasutomo,Nakanishi, Yasue,Yamada, Ken-ichi,Tomioka, Kiyoshi
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supporting information
p. 5309 - 5318
(2018/06/11)
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- C(alkenyl)-H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis
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A catalytic method to prepare highly substituted 1,3-dienes from two different alkenes is described using a directed, palladium(II)-mediated C(alkenyl)-H activation strategy. The transformation exhibits broad scope across three synthetically useful substrate classes masked with suitable bidentate auxiliaries (4-pentenoic acids, allylic alcohols, and bishomoallylic amines) and tolerates internal nonconjugated alkenes, which have traditionally been a challenging class of substrates in this type of chemistry. Catalytic turnover is enabled by either MnO2 as the stoichiometric oxidant or co-catalytic Co(OAc)2 and O2 (1 atm). Experimental and computational studies were performed to elucidate the preference for C(alkenyl)-H activation over other potential pathways. As part of this effort, a structurally unique alkenylpalladium(II) dimer was isolated and characterized.
- Liu, Mingyu,Yang, Pusu,Karunananda, Malkanthi K.,Wang, Yanyan,Liu, Peng,Engle, Keary M.
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supporting information
p. 5805 - 5813
(2018/05/14)
-
- Total syntheses of surinone B, alatanones A–B, and trineurone A
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The total syntheses of four polyketides, surinone B (1), alatanones A–B (2–3), and trineurone A (4) were accomplished through an efficient and unified strategy via one-pot C-acylation reaction coupling 1,3-cyclohexadiones with EDC-activated acids under mild conditions. Alatanone A (2) was found to be a potent anti-microbial agent against Gram-positive and Gram-negative bacteria with MIC 31.25?μg/ml while alatanone B (3) was found to be a potent anti-fungal agent against Cladosporium cladosporioides with MIC 62.5?μg/ml compared to cycloheximide MIC 125?μg/ml. Our methodology allows performing kilogram scale of these scarce polyketides for the development of new antimicrobials.
- Gundoju, Narayana Rao,Bokam, Ramesh,Yalavarthi, Nageswara Rao,Buddana, Sudheer Kumar,Prakasham,Ponnapalli, Mangala Gowri
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- Tridentate Directing Groups Stabilize 6-Membered Palladacycles in Catalytic Alkene Hydrofunctionalization
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Removable tridentate directing groups inspired by pincer ligands have been designed to stabilize otherwise kinetically and thermodynamically disfavored 6-membered alkyl palladacycle intermediates. This family of directing groups enables regioselective remote hydrocarbofunctionalization of several synthetically useful alkene-containing substrate classes, including 4-pentenoic acids, allylic alcohols, homoallyl amines, and bis-homoallylamines, under Pd(II) catalysis. In conjunction with previous findings, we demonstrate regiodivergent hydrofunctionalization of 3-butenoic acid derivatives to afford either Markovnikov or anti-Markovnikov addition products depending on directing group choice. Preliminary mechanistic and computational data are presented to support the proposed catalytic cycle.
- O'Duill, Miriam L.,Matsuura, Rei,Wang, Yanyan,Turnbull, Joshua L.,Gurak, John A.,Gao, De-Wei,Lu, Gang,Liu, Peng,Engle, Keary M.
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supporting information
p. 15576 - 15579
(2017/11/14)
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- Reversing the Regioselectivity of Halofunctionalization Reactions through Cooperative Photoredox and Copper Catalysis
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Halofunctionalization of alkenes is a classical method for olefin difunctionalization. It gives rise to adducts which are found in many natural products and biologically active molecules, and offers a synthetic handle for further manipulation. Classically, this reaction is performed with an electrophilic halogen source and leads to regioselective formation of the halofunctionalized adducts. Herein, we demonstrate a reversal of the native regioselectivity for alkene halofunctionalization through the use of an acridinium photooxidant in conjunction with a copper cocatalyst.
- Griffin, Jeremy D.,Cavanaugh, Cortney L.,Nicewicz, David A.
-
supporting information
p. 2097 - 2100
(2017/02/15)
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- Palladium-Catalyzed Aerobic Oxidative Cyclization of Aliphatic Alkenyl Amides for the Construction of Pyrrolizidine and Indolizidine Derivatives
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An efficient palladium-catalyzed aerobic oxidative cyclization has been developed to synthesize a variety of pyrrolizidine and indolizidine derivatives from simple aliphatic alkenyl amides in moderate to good yields. The reaction features the capability of accessing various N-heterocycles and the use of molecular oxygen (1 atm) as the green oxidant.
- Lo, Kai-Yip,Ye, Liu,Yang, Dan
-
supporting information
p. 1570 - 1575
(2017/08/11)
-
- Synthesis of antifungal alatanone and trineurone polyketides
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The antifungal polyketides alatanones A and B and trineurones A–E have been synthesized using a one-pot C-acylation reaction coupling 1,3-cyclohexanediones with the appropriate carboxylic acids. This key transformation is believed to proceed via initial carbodiimide-mediated O-acylation followed by a DMAP-catalyzed Claisen–Haase rearrangement, resulting in O to C acyl migration.
- Lewis, Alexander R.,Reber, Keith P.
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supporting information
p. 1083 - 1086
(2018/03/23)
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- Preparation of α-Acyloxy Ketones via Visible-Light-Driven Aerobic Oxo-Acyloxylation of Olefins with Carboxylic Acids
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We developed a visible-light driven oxo-acyloxylation of aryl alkenes with carboxylic acids and molecular oxygen. A metal-free photoredox system, consisting of an acridinium photocatalyst, an organic base, and molecular sieve (MS) 4 ?, promotes chemoselective aerobic photooxidation of aryl alkenes. This approach may provide a green, practical, and metal-free protocol for a wide range of α-acyloxy ketones.
- Zhang, Qing-Bao,Ban, Yong-Liang,Zhou, Da-Gang,Zhou, Pan-Pan,Wu, Li-Zhu,Liu, Qiang
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supporting information
p. 5256 - 5259
(2016/11/02)
-
- Gallium-catalyzed reductive lactonization of γ-keto acids with a hydrosilane
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Described herein is the GaCl3-catalyzed lactonization of γ-keto carboxylic acids in the presence of PhSiH3 leading to the direct preparation of γ-lactone derivatives. This reducing system showed a relatively wide functional group tolerance.
- Sakai, Norio,Horikawa, Shuhei,Ogiwara, Yohei
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p. 81763 - 81766
(2016/09/09)
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- Anodic coupling of carboxylic acids to electron-rich double bonds: A surprising non-Kolbe pathway to lactones
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Carboxylic acids have been electro-oxidatively coupled to electron-rich olefins to form lactones. Kolbe decarboxylation does not appear to be a significant competing pathway. Experimental results indicate that oxidation occurs at the olefin and that the reaction proceeds through a radical cation intermediate.
- Perkins, Robert J.,Xu, Hai-Chao,Campbell, John M.,Moeller, Kevin D.
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supporting information
p. 1630 - 1636
(2013/10/22)
-
- Enantioselective bromolactonization of cis-1,2-disubstituted olefinic acids using an amino-thiocarbamate catalyst
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A facile, highly regio- and enantioselective amino-thiocarbamate-catalyzed bromolactonization of cis-1,2-disubstituted olefinic acids has been developed. The use of the enantio-enriched lactones in the synthesis of chiral synthetic intermediates is also demonstrated. 2012
- Tan, Chong Kiat,Le, Chencheng,Yeung, Ying-Yeung
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supporting information; experimental part
p. 5793 - 5795
(2012/08/08)
-
- Catalytic asymmetric synthesis of (S)-laudanosine by hydroamination
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Lithium amide-chiral bisoxazoline-catalyzed asymmetric intramolecular hydroamination was examined with respect to the structural variants of starting aminoalkenes. Substituents on the nitrogen and olefin of aminoalkenes were found to be important factors affecting reaction efficiency as well as enentioselectivity in the production of chiral tetrahydroisoquinolines and isoindolines. The catalytic asymmetric total synthesis of (S)-laudanosine highlights the utility of the asymmetric hydroamination.
- Ogata, Tokutaro,Kimachi, Tetsutaro,Yamada, Ken-Ichi,Yamamoto, Yasutomo,Tomioka, Kiyoshi
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p. 469 - 485
(2013/08/23)
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- Aminothiocarbamate-catalyzed asymmetric bromolactonization of 1,2-disubstituted olefinic acids
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An efficient and enantioselective bromolactonization of 1,2-disubstituted olefinic acids using an amino-thiocarbamate catalyst has been developed, resulting in the formation of δ-lactones containing two chiral centers with up to 99% yield, 95% ee.
- Tan, Chong Kiat,Zhou, Ling,Yeung, Ying-Yeung
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supporting information; experimental part
p. 2738 - 2741
(2011/06/26)
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- Selenium-catalyzed regioselective cyclization of unsaturated carboxylic acids using hypervalent iodine oxidants
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A new and convenient selenium-catalyzed regioselective cyclization of γ, δ-unsaturated carboxylic acids to the corresponding 3, 6-dihydro-2Hpyran- 2-ones is described. The cyclization products have been obtained in good to excellent yields using diphenyl diselenide as a catalyst and [bis(trifluoroacetoxy)iodo]benzene as a stoichiometric oxidant 2011 American Chemical Society.
- Singh, Fateh V.,Wirth, Thomas
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supporting information; experimental part
p. 6504 - 6507
(2012/02/02)
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- Acyloxylactonisations mediated by lead tetracarboxylates
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The reaction of lead(IV) tetracarboxylates with carboxylic acids containing unsaturated side chains has been found to give acyloxy lactone products in a diastereoselective process; the reaction can be extended to lead(IV) tetrazolates to give the analogous outcome. Mechanistic implications of these results are discussed.
- Cottrell, Ian F.,Cowley, Andrew R.,Croft, Laura J.,Hymns, Lauren,Moloney, Mark G.,Nettleton, Ewan J.,Kirsty Smithies,Thompson, Amber L.
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supporting information; experimental part
p. 2537 - 2550
(2009/08/07)
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- Solvent and ligand partition reaction pathways in nickel-mediated carboxylation of methylenecyclopropanes
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Methylenecyclopropanes are carboxylated with gaseous carbon dioxide in the presence of a stoichiometric amount of a nickel complex; the reaction pathways are significantly influenced by the reaction solvent and the amine ligand. The Royal Society of Chemi
- Murakami, Masahiro,Ishida, Naoki,Miura, Tomoya
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p. 643 - 645
(2008/02/10)
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- One-pot regio- and stereoselective cyclization of 1,2,n-triols
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A simple and efficient process to cyclize triols containing a 1,2-diol functionality with a pendant hydroxyl group is presented. The one-pot procedure converts the 1,2-diol into an ortho ester in situ, which upon treatment with a Lewis acid generates a cyclic acetoxonium intermediate. This intermediate is subsequently trapped by the pendant hydroxyl group to generate a cyclic ether. The stereochemistry of the 1,2-diol is transferred to the product with complete fidelity (inversion at the site of cyclization), and the reaction proceeds with high regioselectivity. The process is akin to the Lewis acid-catalyzed intramolecular ring-opening of epoxides with hydroxyl groups yielding cyclic ethers of various sizes with regio- and stereochemical control. Copyright
- Zheng, Tao,Narayan, Radha S.,Schomaker, Jennifer M.,Borhan, Babak
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p. 6946 - 6947
(2007/10/03)
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- Reagent-Controlled Asymmetric Iodolactonization Using Cinchona Alkaloids as Chiral Sources
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A novel method for reagent-controlled asymmetric iodolactonization of 5-aryl-4-pentenoic acids is reported. This work uses carboxylate ion pairs combined with cinchona alkaloids as chiral sources of carboxylate anion for the first time leading to a mixture of two regio-isomeric iodolactones with moderate enantioselectivity (exo-18.5% ee, endo-35.0% ee) under mild reaction conditions.
- Wang, Mang,Gao, Lian Xun,Yue, Wei,Mai, Wen Peng
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p. 1023 - 1032
(2007/10/03)
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- Transition-metal catalyzed synthesis of δ-hydroxy-γ-lactones from bis(trimethylsilyl) ketene acetals and allylic acetates via γ-unsaturated carboxylic acids. Comments on the formation of α-cyclopropyl carboxylic acids
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Bis(trimethylsilyl)ketene acetals react with allylic acetates in the presence of Pd(0) complexes to give γ-unsaturated carboxylic acids together with α-cyclopropyl carboxylic acids. The unsaturated acids can be converted catalytically to δ-hydroxy-yγ-lactones by the H2O2/MTO system (methyltrioxorhenium) and to butenolides by Pd(II) catalyzed intramolecular cyclization reactions. The structure of two of these lactones has been established by X-ray analysis. The mechanism of the formation of the cyclopropanic acids will be discussed.
- Rudler, Henri,Harris, Paul,Parlier, Andrée,Cantagrel, Frédéric,Denise, Bernard,Bellassoued, Moncef,Vaissermann, Jacqueline
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p. 186 - 202
(2007/10/03)
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- ATP-citrate lyase as a target for hypolipidemic intervention. Design and synthesis of 2-substituted butanedioic acids as novel, potent inhibitors of the enzyme
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ATP-citrate lyase is the primary enzyme responsible for the synthesis of cytosolic acetyl-CoA in many tissues. Inhibitors of the enzyme represent a potentially novel class of hypolipidemic agent, which are anticipated to have combined hypocholesterolemic and hypotriglyceridemic properties. A series of 2-substituted butanedioic acids have been designed and synthesized as inhibitors of the enzyme. The best compounds, 58, 68, 71, 74 have reversible K(i)'s in the 1-3 μM range against the isolated rat enzyme. As representative of this compound class, 58, has been shown to exert its inhibitory action through a mainly competitive mechanism with respect to citrate and a noncompetitive one with respect to CoA. None of the inhibitors were able to inhibit cholesterol and/or fatty acid synthesis in HepG2 cells. This has been attributed to the adverse physicochemical properties of the molecules leading to a lack of cell penetration. Despite this, a lead structural class of compound has been identified with the potential for modification into potent, cell-penetrant, and efficacious inhibitors of ATP- citrate lyase.
- Gribble, Andrew D.,Dolle, Roland E.,Shaw, Antony,McNair, David,Novelli, Riccardo,Novelli, Christine E.,Slingsby, Brian P.,Shah, Virendra P.,Tew, David,Saxty, Barbara A.,Allen, Mark,Groot, Pieter H.,Pearce, Nigel,Yates, John
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p. 3569 - 3584
(2007/10/03)
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- Process for the preparation of carboxylic acids and derivatives of them
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The subject matter of the invention is a process for the preparation of carboxylic acids and derivatives of them of the general formula STR1 wherein R means hydrogen, or a C1-4 alkyl or a (C1-5 alkoxy)carbonyl group, R1 is as defined in claim 1, R7 stands for hydrogen or a C1-7 alkyl group and R8 means hydrogen or a carboxyl group, by reacting a 1,3-dioxane-4,6-dione derivative of the general formula STR2 wherein R9 stands for a C1-4 alkyl group or a phenyl group, optionally monosubstituted by halogen and R10 stands for hydrogen or a C1-5 alkyl group or R9 and R10 together form a pentamethylene group, and an aldehyde or ketone of the general formula STR3 in the presence of formic acid.
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-
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- Process for the preparation of carboxylic acids and derivatives of them
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The subject matter of the invention is a process for the preparation of carboxylic acids and derivatives of them of the general formula wherein Rmeans hydrogen, or a C1 4alkyl or a (C1 5alkoxy)carbonyl group, R1is as defined in claim 1, R7stands for hydrogen or a C1 7alkyl group and R8means hydrogen or a carboxyl group, by reacting a 1,3-dioxane-4,6-dione derivative of the general formula wherein R9stands for a C1 4alkyl group or a phenyl group, optionally monosubstituted by halogen and R10stands for hydrogen or a C1 5alkyl group or R9 and R10together form a pentamethylene group, and an aldehyde or ketone of the general formula in the presence of formic acid and of [a] amine(s) and, if desired, of an alcohol of the general formula, , R7 - OH VI,, , wherein R7is a C1 7alkyl group, at a temperature of 20 to 140°C, and/or, reducing an unsaturated 1,3-dioxane-4,6-dione derivative of the general formula and/or, a 1,3-dioxane-4,6-dione derivative of the general formula with formic acid in the presence of [a] amine(s) and, if desired, of an alcohol as above defined.
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- Stereoselective synthesis of 4- or 5-substituted 2-benzyl- and 2-benzoylpyrrolidines by means of anodic oxidation of δ-alkenylamines
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The anodic oxidation of the lithium amides of δ-alkenylamines 6a, 6b, 6c, 10a, and 10b gave stereoselectively cis-5-substituted 2-benzyl-1-methylpyrrolidines (7a, 7b, 7c) and 4-substituted 2-benzyl-1-methyl-pyrrolidines (11a, 11b) in high yields. The anod
- Tokuda,Miyamoto,Fujita,Suginome
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p. 747 - 756
(2007/10/02)
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- Photophysical and photochemical behavior of intramolecular-styrene-amine exciplexes
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The photophysical and photochemical behavior of a series of secondary and tertiary ω-(β-styryl)aminoalkanes with one to five methylenes separating the styryl and amino groups has been investigated and compared to the intermolecular reactions of 1-phenylpropene with secondary and tertiary amines. The tertiary styrylamines form fluorescent intramolecular exciplexes, but fail to undergo intramolecular addition reactions. Both the rate constant for exciplex formation and the stability of the exciplex are dependent upon the length of the polymethylene chain connecting the chromophores. The failure of the tertiary amine exciplexes to undergo intramolecular addition is attributed to an unfavorable exciplex geometry for α-C-H transfer to the styrene double bond. While the secondary styrylamines do not form fluorescent exciplexes, the dependence of the styrene singlet lifetime upon the polymethylene chain length is similar to that for the tertiary styrylamines. Intramolecular N-H addition to the styrene double bond results in the formation of two regioisomeric (α-phenyl and α-benzyl) cyclic amines of different ring size. The regioisomer of larger ring size is favored except in the case in which four methylenes separate the chromophores. The effects of polymethylene chain length, solvent polarity, temperature, and the bulk of the N-alkyl group upon product yields and ratios are discussed in terms of a mechanism involving singlet exciplex and biradical intermediates.
- Lewis, Frederick D.,Dasharatha Reddy,Schneider, Siegfried,Ga, Michael
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p. 3498 - 3506
(2007/10/02)
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- STUCTURE AND SYNTHESIS OF WF 3681, A NOVEL ALDOSE REDUCTASE INHIBITOR
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The structure of WF 3681 (1), an aldose reductase inhibitor isolated from a Chaetomella species, has been determined on the basis of its physical and chemical properties and confirmed by a total synthesis.
- Uchida, Itsuo,Itoh, Yoshikuni,Namiki, Takayuki,Nishikawa, Motoaki,Hashimoto, Masashi
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p. 2015 - 2018
(2007/10/02)
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- REACTIVITY OF 1-CYCLOPROPENE-1-LACTONES DEPENDENT ON THE SUSBSTITUTION DEGREE
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Reaction of the α-chloro lactone 10 with KOtBu gives the butoxy lactones 21 and 22; the seven membered derivative 11 leads 23 as the only isolable product.Formation of the α-substitution product 21 as well as the enhanced instability of the intermediates 12 and 13 in comparison to their methyl substituted homologues 5 and 6 show the kinetical stabilization by a methyl group at C-2.Products derived from a cyclopropeno lactone of type A could not be detected.
- Hashem, Md. Abul,Weyerstahl, Peter
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p. 2003 - 2010
(2007/10/02)
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- ANOMALOUS STEREOCHEMISTRY IN THE WITTIG REACTION INDUCED BY NUCLEOPHILIC GROUPS IN THE PHOSPHONIUM YLIDE
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Reaction of ylides from 3-9 with benzaldehyde show that carboxylate and oxido functionalities proximate to the ylide center promote anomalously high E stereoselectivity in alkene formation.Through the use of α-deuterated ylides 12-14, an internal "trans-selective Wittig" mechanism was ruled out as a principal source of exaggerated E alkene production.
- Maryanoff, Bruce E.,Duhl-Emswiler, B. A.,Reitz, Allen B.
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p. 187 - 190
(2007/10/02)
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