- Rhodium-Catalyzed β-Dehydroborylation of Silyl Enol Ethers: Access to Highly Functionalized Enolates
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An efficient rhodium-catalyzed β-dehydroborylation of aldehyde-derived silyl enol ethers (SEEs) with bis(pinacolato)diboron (B2pin2) is disclosed. The borylation reactions proceeded well with alkyl- and aryl-substituted SEEs, affording a wide array of valuable functionalized β-boryl silyl enolates with high efficiency and excellent stereoselectivity. Moreover, the borylated products, through versatile carbon–boron bond transformations, were readily converted into diverse synthetically useful molecules, including α-hydroxy ketones, functionalized SEEs, and gem-difunctionalized aldehydes.
- Li, Jie,Li, Ruoling,Yang, Wen,Zhao, Pei,Zhao, Wanxiang
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supporting information
p. 9580 - 9585
(2021/12/14)
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- Three-Component Alkene Difunctionalization by Direct and Selective Activation of Aliphatic C?H Bonds
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Catalytic alkene difunctionalization is a powerful strategy for the rapid assembly of complex molecules and has wide range of applications in synthetic chemistry. Despite significant progress, a compelling challenge that still needs to be solved is the installation of highly functionalized C(sp3)-hybridized centers without requiring pre-activated substrates. We herein report that inexpensive and easy-to-synthesize decatungstate photo-HAT, in combination with nickel catalysis, provides a versatile platform for three-component alkene difunctionalization through direct and selective activation of aliphatic C?H bonds. Compared with previous studies, the significant advantages of this strategy are that the most abundant hydrocarbons are used as feedstocks, and various highly functionalized tertiary, secondary, and primary C(sp3)-hybrid centers can be easily installed. The practicability of this strategy is demonstrated in the selective late-stage functionalization of natural products and the concise synthesis of pharmaceutically relevant molecules including Piragliatin.
- Xu, Sheng,Chen, Herong,Zhou, Zhijun,Kong, Wangqing
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supporting information
p. 7405 - 7411
(2021/02/20)
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- Efficient C-H Amination Catalysis Using Nickel-Dipyrrin Complexes
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A dipyrrin-supported nickel catalyst (AdFL)Ni(py) (AdFL: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine) displays productive intramolecular C-H bond amination to afford N-heterocyclic products using aliphatic azide substrates. The catalytic amination conditions are mild, requiring 0.1-2 mol% catalyst loading and operational at room temperature. The scope of C-H bond substrates was explored and benzylic, tertiary, secondary, and primary C-H bonds are successfully aminated. The amination chemoselectivity was examined using substrates featuring multiple activatable C-H bonds. Uniformly, the catalyst showcases high chemoselectivity favoring C-H bonds with lower bond dissociation energy as well as a wide range of functional group tolerance (e.g., ethers, halides, thioetheres, esters, etc.). Sequential cyclization of substrates with ester groups could be achieved, providing facile preparation of an indolizidine framework commonly found in a variety of alkaloids. The amination cyclization reaction mechanism was examined employing nuclear magnetic resonance (NMR) spectroscopy to determine the reaction kinetic profile. A large, primary intermolecular kinetic isotope effect (KIE = 31.9 ± 1.0) suggests H-atom abstraction (HAA) is the rate-determining step, indicative of H-atom tunneling being operative. The reaction rate has first order dependence in the catalyst and zeroth order in substrate, consistent with the resting state of the catalyst as the corresponding nickel iminyl radical. The presence of the nickel iminyl was determined by multinuclear NMR spectroscopy observed during catalysis. The activation parameters (ΔH? = 13.4 ± 0.5 kcal/mol; ΔS?= -24.3 ± 1.7 cal/mol·K) were measured using Eyring analysis, implying a highly ordered transition state during the HAA step. The proposed mechanism of rapid iminyl formation, rate-determining HAA, and subsequent radical recombination was corroborated by intramolecular isotope labeling experiments and theoretical calculations.
- Betley, Theodore A.,Clarke, Ryan M.,Dong, Yuyang,Porter, Gerard J.
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supporting information
p. 10996 - 11005
(2020/07/08)
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- TRICYCLIC COMPOUND SERVING AS IMMUNOMODULATOR
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Provided are compounds of formula I and formula II or pharmaceutically acceptable salts of the compounds and pharmaceutical compositions thereof. The compounds of formula I and formula II or the pharmaceutically acceptable salts of the compounds provide indole 2,3-dioxygenase (IDO) inhibitory activity and are capable of treating IDO-mediated immunosuppressive diseases, such as infectious diseases or cancer.
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-
Paragraph 0216-0217
(2019/01/04)
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- Sunlight-driven trifluoromethylation of olefinic substrates by photoredox catalysis: A green organic process
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The principles and utility of photoredox catalysis in organic synthesis are described. After a brief description of the features of the two types of catalytic photoredox processes following the reductive quenching cycle (RQC) and the oxidative quenching cycle (OQC), the discussion is focused on organic transformations based on OQC, in particular the trifluoromethylation of olefinic substrates with electrophilic trifluoromethylating reagents furnishing solvolytic addition products and substitution products. It is concluded that catalytic photoredox systems are green from the point of view of harmfulness, safety, and energy source (visible light, including sunlight). Future prospects of photoredox catalysis will be also discussed.
- Akita, Munetaka,Koike, Takashi
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p. 742 - 751
(2015/07/15)
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- Synthesis of novel 3-cyclohexylpropanoic acid-derived nitrogen heterocyclic compounds and their evaluation for tuberculostatic activity
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A series of novel 3-cyclohexylpropanoic acid derivatives and 3-cyclohexylpropanoic acid-derived nitrogen heterocyclic compounds (1-8) have been synthesized and evaluated for tuberculostatic activity. Compounds 1a, 1c, 1e and 1f bearing benzimidazole or benzimidazole-like systems showed the most potent tuberculostatic activity against Mycobacterium tuberculosis strains with MIC values ranging from 1.5 to 12.5 μg/mL. More importantly 1a (6-chloro-2-(2-cyclohexylethyl)-4-nitro-1H-benzo[d]imidazole) and 1f (2-(2-cyclohexylethyl)-1H-imidazo[4,5-b]phenazine) appeared selective for M. tuberculosis as compared with eukaryotic cells (human fibroblasts), and other antimicrobial strains. These compounds may thus represent a novel, selective class of antitubercular agents. Additionally compound 1a stimulated type I collagen output by fibroblasts, in vitro.
- Gobis, Katarzyna,Foks, Henryk,Bojanowski, Krzysztof,Augustynowicz-Kope?, Ewa,Napiórkowska, Agnieszka
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experimental part
p. 137 - 144
(2012/03/08)
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- Visible light-induced selective generation of radicals from organoborates by photoredox catalysis
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A new strategy for the generation of carbon-centered radicals via oxidation of alkyl-, allyl-, benzyl- and arylborates by visible-light-driven single electron transfer (SET) photoredox catalysis has been established. The generated radicals smoothly react with TEMPO and electron-deficient alkenes to afford C-O and C-C coupling products, respectively. In this radical initiating system, cyclic organo(triol)borates turn out to be useful radical precursors.
- Yasu, Yusuke,Koike, Takashi,Akita, Munetaka
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p. 3414 - 3420
(2013/02/25)
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- A simple and highly effective method for hydrogenation of arenes by [Rh(COD)Cl]2
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Hydrogenation of arenes, including chiral BINOLs and the lignin model compounds, has been achieved efficiently by using the simple complex [Rh(COD)Cl]2 as catalyst precursor.
- Wang, Da-Wei,Lu, Sheng-Mei,Zhou, Yong-Gui
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supporting information; experimental part
p. 1282 - 1285
(2009/09/06)
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- Tetrabutylammonium decatungstate-photosensitized alkylation of electrophilic alkenes: Convenient functionalization of aliphatic C-H bonds
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Tetrabutylammonium decatungstate (TBADT, 2×10-3M) is an effective photocatalyst for the alkylation of electrophilic alkenes (0.1 M, α,β-unsaturated nitriles, esters, ketones) by alkanes, alcohols, and ethers. The products are in most cases obtained in >70% isolated yields, through an experimentally very simple procedure. The kinetics of the radical processes following initial hydrogen abstraction by excited TBADT in deoxygenated MeCN have been studied. In the absence of a trap, back hydrogen transfer from reduced tungstate is the main pathway for alkyl radicals, while α-hydroxyalkyl radicals are oxidized to ketones by ground-state TBADT. With both radical types the reaction ceases at a few percent conversion. However, trapping by electrophilic alkenes is followed by reduction of the radical adduct and regeneration of the catalyst, which allows the alkylation to proceed up to complete alkene conversion with the mentioned good yields of products. With a nucleophilic (α-hydroxyalkyl) radical, alkylation is efficient (Φ = 0.58) and can also be carried out when degassing is omitted, the only difference being a short induction period. With a less reactive (cyclohexyl) radical, the quantum yield is lower (Φ = 0.06) and the reaction is considerably slowed in aerated solutions, but the chemical yield remains good.
- Dondi, Daniele,Fagnoni, Maurizio,Albini, Angelo
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p. 4153 - 4163
(2007/10/03)
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- Radical deoxygenation of alcohols and intermolecular carbon-carbon bond formation with surfactant-type radical chain carriers in water
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An efficient and mild method is developed for radical deoxygenation of alcohols and formation of carbon-carbon bonds in water without adding additives such as surfactants. The reaction was applied to synthesis of 2′,3′-didehydro-2′,3′-dideoxynucleosides that are potent anti-HIV agents. The reaction afforded environmentally benign reaction conditions.
- Cho, Dae Hyan,Jang, Doo Ok
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p. 1799 - 1802
(2007/10/03)
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- Solvent-modulated chemoselective deprotections of trialkylsilyl esters and chemoselective esterifications
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A series of trialkylsilyl esters were deprotected or transesterificated into their corresponding carboxylic acids or methyl esters under a catalytic amount of CBr4 in alcohol reaction system. This method enables to desilylate secondary sp3-carbon, sp2-carbon, sp-carbon and aryl tethered trialkylsilyl esters to carboxylic acids, whereas primary sp 3-carbon tethered trialkylsilyl esters were further converted into their methyl esters under CBr4/MeOH reaction conditions. The highly chemoselective deprotections can be modulated and achieved by the introduced protecting trialkylsilyl groups and the used alcohols such as MeOH and EtOH under this photochemically-induced reaction conditions.
- Lee, Adam Shih-Yuan,Su, Feng-Yih
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p. 6305 - 6309
(2007/10/03)
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- A Simple and Efficient Esterification Method
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A convenient and practical esterification was realized and this reaction proceeded without a dehydrating reagent or water removal equipment. The synthesis of esters by reaction of carboxylic acids with various alcohols such as methyl, ethyl, isopropyl, isobutyl, allyl, benzyl, propargyl and decanyl alcohols were achieved with a catalytic amount of CBr4 under refluxing reaction condition.
- Ming-Yi, Chen,Lee, Adam Shih-Yuan
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p. 103 - 108
(2007/10/03)
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- N-Ethylpiperidine Hypophosphite Mediated Intermolecular Radical Carbon-Carbon Bond Forming Reaction in Water
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N-Ethylpiperidine hypophosphite mediated radical addition reactions to electron deficient alkenes in aqueous media have been developed. The reactions afford high isolated yields of addition products without using a large excess of alkenes.
- Jang, Doo Ok,Cho, Dae Hyan
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p. 1523 - 1525
(2007/10/03)
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- An unprecedented and highly chemoselective esterification method
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A series of carboxylic acids was transformed to their corresponding methyl esters under CBr4/CH3OH (0.05 eq., 5 ml) reaction conditions. The rate of esterification is decreased with increasing bulkiness of the alcohol. Chemoselectivity can be achieved between phenylacetic and benzoic acids, sp3-C and sp2-C acids as well as between sp3-C and sp-C tethered carboxylic acids.
- Lee, Shih-Yuan Adam,Yang, Hui-Chun,Su, Feng-Yih
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p. 301 - 303
(2007/10/03)
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- PHOSPHINE NICKEL COMPLEX AS CATALYST IN REACTIONS OF ORGANIC BROMIDES RBr WITH α,β-UNSATURATED KETONES, NITRILES, AND ESTERS. CONJUGATE ADDITION OF R GROUP AND H ATOM ACROSS THE C=C BOND
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Reactions of organic bromides, particularly of secondary and tertiary alkyl bromides, with α,β - unsaturated carbonyl compounds and acrylonitryle in the presence of the catalytic system nickel complex-zinc result in formation of products of conjugate addition of the organic moiety of the bromide and a hydrogen atom across the C=C double bond of the unsaturated substrate.
- Lebedev, S. A.,Lopatina, V. S.,Petrov, E. S.
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p. 444 - 446
(2007/10/03)
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- Rate constants for the additions of cyclohexyl radical to acrylamides, imides and sulfonimides
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Competition experiments are used to provide estimated rate constants for the addition of cyclohexyl radical to a series of acrylamides, imides and sulfonimides.
- Curran,Qi,Porter,Su,Wu
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p. 4489 - 4492
(2007/10/02)
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- Chromium(II)-Mediated Intermolecular Free-Radical Carbon-Carbon Bond Formation
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Chromium(II) complexes are found to be effective mediators for intermolecular free-radical C-C bond formation.Thus, Cr(en)2(2+) species react with alkyl halides to generate the corresponding alkyl radicals which are readily trapped with electron-deficient alkenes to afford the coupling products.Key Words: Radicals / Bond formation, C-C / Chromium(II) complexes
- Tashtoush, Hasan I.,Sustmann, Reiner
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p. 287 - 289
(2007/10/02)
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- Dimeric Metal Complexes as Mediator for Radical C-C Bond-Forming Reactions
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Irradiation of dicarbonyl(η5-cyclopentadienyl)iron dimer 1 or decacarbonyldimanganese (2) in the presence of alkyl halides leads to C-centered radicals which can be trapped by alkenes and yields saturated and/or unsaturated addition products.Carbon radicals are generated via halogen abstraction by the initially formed metal-centered radicals resulting from homolysis of the metal-metal bond of dimeric mediators 1 and 2.No reaction occurs using octacarbonyl dicobalt (3).
- Giese, Bernd,Thoma, Gebhard
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p. 1135 - 1142
(2007/10/02)
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- Synthese et reactivite d'un nouvel hydrure organostannique a "queue polaire": le dibutyl-4,7,10-trioxaundecylstannane
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A new tin hydride was prepared by reduction of the tin chloride obtained in the addition of hydrogenochlorodibutylstannane to the allyl methyl ether of diethylenehglycol.The efficiency of this compound in reductions and reductive additions to alkenes of alkyl halides was demonstrated as well as the easy separation of the organic products of reaction from the organotin compounds by liquid-solid chromatography over silica.
- Ferkous, F.,Messadi, D.,Jeso, B. De,Degueil-Castaing, M.,Maillard, B.
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p. 315 - 320
(2007/10/02)
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- Alkyl isocyanides as precursors for the formation of carbon-carbon bonds
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Tris(trimethylsilyl)silane is an effective mediator for the formation of carbon-carbon bonds via radicals using alkyl isocyanides as precursors.
- Chatgilialoglu,Giese,Kopping
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p. 6013 - 6016
(2007/10/02)
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- TRIS(TRIMETHYLSILYL)SILANE AS MEDIATOR IN ORGANIC SYNTHESIS VIA RADICALS
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Silane 3 is an effective mediator in organic synthesis via radicals.Reactions with this silane give smaller amounts of unwanted reduction products than reactions with toxic stannanes.
- Giese, Bernd,Kopping, Birgit,Chatgilialoglu, Chryssostomos
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p. 681 - 684
(2007/10/02)
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- GENERATION AND SYNTHETIC USE OF ALKYL RADICALS WITH 2 AS MEDIATOR
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Irradiation of dimeric iron complex 1 in the presence of alkyl halides yields alkyl radicals that are useful in organic synthesis.
- Thoma, Gebhard,Giese, Bernd
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p. 2907 - 2910
(2007/10/02)
-
- 13C Chemical Shift Non-Equivalence in Methylene Carbons of Monosubstituted Cyclohexanes
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Monosubstituted cyclohexanes were synthesized by addition of a cyclohexyl radical to olefins bearing different substituents at the α-position.Six distinct methylene 13C resonances were observed, indicating that the methylene carbons located at the 2 and 6 positions and at 3 and 5 positions are not magnetically equivalent.This magnetic non-equivalence (anisochronism) observed in the monosubstituted cyclohexanes is due to the introduction of an asymmetric center β to the prochiral C-1 ring carbon atom. KEY WORDS Anisochronism Magnetic non-equivalence Cyclohexyl adducts Mercury method
- Ito, Hiroshi,Renaldo, Alfred F.,Johnson, Robert D.,Ueda, Mitsuru
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p. 273 - 276
(2007/10/02)
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- Condensation of organic bromides with vinyl compounds catalysed by nickel complexes in the presence of zinc
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The catalytic system (Ph3P)2NiCl2/zinc/pyridine in acetonitrile is an effective catalyst for reactions of aryl and alkyl bromides with styrene and methyl acrylate.With styrene, the reaction yields vinyl hydrogen replacement (condensation) products, viz. stilbenes and β-alkylstyrenes.Methyl acrylate reacts to give conjugated addition (hydrocondensation) products, methyl esters of β-aryl and β-alkyl propionic acids.
- Lebedev, S. A.,Lopatina, V. S.,Petrov, E. S.,Beletskaya, I. P.
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p. 253 - 260
(2007/10/02)
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- 2,5,6,7-tetranor-4,8-inter-m-phenylene PGI2 derivatives
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Disclosed herein are novel prostaglandin I2 (PGI2) derivatives exhibiting excellent in vivo duration and activities, said derivatives being represented by the general formula: STR1 wherein R1, X, R2 and R3 are as defined herein.
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-
-
- NOVEL 5-AMINO-4-HYDROXYVALERYL DERIVATIVES
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Compounds of the formula STR1 in which R 1 represents hydrogen or acyl, A represents an optionally N-alkylated α-amino acid residue which is bonded N-terminally to R 1 and C-terminally to the group--NR 2--, R 2 represents hydrogen or lower alkyl, R 3 represents hydrogen, lower alkyl, optionally etherified or esterified hydroxy-lower alkyl, cycloalkyl, cycloalkyl-lower alkyl, bicycloalkyl-lower alkyl, tricycloalkyl-lower alkyl, aryl or aryl-lower alkyl, R 4 represents hydroxy or etherified or esterified hydroxy, R 5 represents lower alkyl having 2 or more carbon atoms, optionally etherified or esterified hydroxy-lower alkyl, cycloalkyl, cycloalkyl-lower alkyl, bicycloalkyl, bicycloalkyl-lower alkyl, tricycloalkyl, tricycloalkyl-lower alkyl, aryl, aryl-lower alkyl, optionally substituted carbamoyl, optionally substituted amino, optionally substituted hydroxy or optionally substituted mercapto and R 6 represents substituted amino, and salts of such compounds having salt-forming groups inhibit the blood pressure-increasing action of the enzyme renin and can be used as antihypertensives.
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-
-
- Thermal Addition of Alkanes to Alkenes, IV. Regioselectivity in the Addition of Cyclohexane to 1,2-Disubstituted Alkenes
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Alkanes can be added to alkenes in a free radical chain reaction ("ane reaction").Regioselectivity in the addition of cyclohexane to (E)-3-alkyl substituted methyl acrylates have been measured at 300-450C.The ratio of the two regioisomers 3 and 4 shows a correlation with steric substituent constants Es.Relative rates of the addition of cyclohexyl radical to the alkene and β-scission of the adduct radical versus H-transfer from cyclohexane are determining the ratio of the regioisomers.A minor temperature dependence of regioselectivity has been observed.In relation to the products 3 and 4, ane reaction at a temperature of 450C can be more selective than radical addition reaction at room temperature.Regioselectivity of the addition of cyclohexane to methyl cinnamate at 360-420C shows a slight polar substituent effect.Electron withdrawing substituents have been shown to increase product ratio 4/3.
- Metzger, Juergen O.,Klenke, Kurt,Hartmanns, Joerg,Eisermann, Doris
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p. 508 - 513
(2007/10/02)
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- CARBOMETHOXYETHYLATION OF ARYL AND ALKYL BROMIDES CATALYZED BY NICKEL COMPLEXES
-
The reaction of aryl and alkyl bromides with methyl acrylate in the presence of water, pyridine, and a nickel catalyst results in the formation of saturated conjugate-addition products, viz. methyl esters of aryl- and alkylpropionic acids.
- Lebedev, S. A.,Lopatina, V. S.,Berestova, S. S.,Petrov, E. S.,Beletskaya, I. P.
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p. 1238 - 1241
(2007/10/02)
-
- On the cis-Effect of Radical Addition Reactions at Alkenes
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The trans-alkenes 2e - h react faster with cyclohexyl radicals than the cis-alkenes 3e - h (Table 1).Radical addition reactions at alkylidenemalonic esters 1 show that this cis-effect increases with the bulkyness of the substituents (Table 1).However, the difference in the reactivity between trans- and cis-alkenes exerts no effect on the regioselectivity (Table 3).It is concluded that the reason for the cis-effect is a twisting of the ?-system that influences the reactivity of both vinylic C-atoms to the same extent.
- Giese, Bernd,Lachhein, Stephen
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p. 1616 - 1620
(2007/10/02)
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- Phenyl Effects in Radical Additions to Alkenes
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Reactions of cyclohexylmercuric salts 4 with NaBH4 in the presence of alkenes 8 yield products 10.The main step of the reaction sequence, the addition of a cyclohexyl radical (7) to alkene 8, can be measured using a competition technique.The data show that styrene reacts 30 - 40 times faster than expected by the ?p--value.This phenyl effect decreases in going from monosubstituted alkenes 8 to disubstituted alkenes 3, 2 and 1 because the steric hindrance of a coplanar orientation of the ?-system increases in the same order.
- Giese, Bernd,Kretzschmar, Gerhard
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p. 3267 - 3270
(2007/10/02)
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- Polar Substituent Effects in Additions of Alkyl Radicals to Alkenes
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Reduction of cyclohexylmercuric salts (7) with NaBH4 yields cyclohexyl radicals (8).Their rel. rates of addition to substituted styrenes 4, acrylic esters 5 and acrylonitriles 6 have been measured.Comparison with Hammett ?-values shows, that substituents at the non attacked vinylic carbon atom show polar effects mainly (Table 1).The effect of a substituent variation increases with increase of the reactivity of the alkenes (Table 2).Mesomeric and steric effects play only a minor role.
- Giese, Bernd,Meixner, Juergen
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p. 2138 - 2145
(2007/10/02)
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- HOCHDRUCK-HOCHTEMPERATUR-REAKTIONEN IN EINEM STROEMUNGSREAKTOR-VI. THERMISCHE ADDITION VON ALKANEN AN ALKENE
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The thermal Anti-Markownikow-addition of alkanes to activated and desactivated alkenes ("direkte substituierende Addition", "Ane-reaction") at 650-723 K and reaction times of 1-10 min. is described.
- Metzger, Juergen,Hartmanns, Joerg,Koell, Peter
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p. 1891 - 1894
(2007/10/02)
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