- Rhodium(III)-Catalyzed Selective Monoarylation of β or γ C(sp3)-H Bonds Assisted by a Trimethylpyrazole Group
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The selective arylation of unactivated β or challenging γ primary and secondary β-C(sp3)-H bonds has been developed with a Cp*Rh(III) catalyst assisted by a trimethylpyrazole group. A rarely reported six-membered rhodacycle has been identified in rhodium-catalyzed C(sp3)-H activation reactions. Preliminary mechanistic studies have revealed that a concerted metalation-deprotonation pathway might be involved in the C-H activation step.
- Yuan, Chunchen,Tu, Guangliang,Zhao, Yingsheng
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- Didecyldimethylammonium bromide (DDAB): a universal, robust, and highly potent phase-transfer catalyst for diverse organic transformations
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Didecyldimethylammonium bromide (DDAB) has been scrutinized in comparison with traditional phase-transfer catalysts in variety of liquid-liquid reactions. It was found to be an exceptionally comprehensive, durable, and highly efficient phase-transfer catalyst (PTC) in a number of representative organic transformations such as C- and N-alkylations, isomerization, esterification, elimination, cyanation, bromination, and oxidation under very mild conditions of temperature and mixing. It was confirmed that DDAB is an exceedingly accessible and concurrently a highly liphophilic phase-transfer catalyst. This unprecedented characteristic renders DDAB to be a multipurpose catalyst that functions effectively both in mass transfer controlled and chemically controlled phase-transfer reactions.
- Chidambaram, Mandan,Sonavane, Sachin U.,de la Zerda, Jaima,Sasson, Yoel
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- Electronic properties of a cationic triphenylphosphine ligand decorated with a (η5-C5H5)Fe group in late-transition-metal complexes
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The synthesis and characterization of a series of novel cationic multimetallic transition-metal complexes based on the cationic phosphine ligand (η6-diphenylphosphinobenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate (1) are reported. Complexes of ligand 1 with the late transition metals ruthenium, osmium, rhodium, and iridium as well as palladium and platinum were isolated in generally good yields, and the solid-state structures of most of them were determined. On the basis of the 195Pt?31P NMR coupling constant measured for trans-(1)2PtCl2 and the carbonyl absorption band in the IR spectrum of trans-(1)2Rh(CO)Cl, the electronic influence of the ligand on the metal center was evaluated. These measurements are supported by density functional theory (DFT) calculations, performed on the corresponding tricarbonylnickel(0) complex in order to determine the Tolman electronic parameter (TEP) of ligand 1.
- Malchau, Christian,Loose, Florian,Mees, Yannick,Duppe, Jens,Sun, Yu,Niedner-Schatteburg, Gereon,Thiel, Werner R.
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- Diastereomer-differentiating photochemistry of β-arylbutyrophenones: Yang cyclization versus type II elimination
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The diastereomers of ketones 2 and 3 are shown to exhibit distinct photochemical reactivities due to conformational preferences; while the anti isomers of 2 and 3 undergo efficient Yang cyclization in 75-90% yields with a remarkable diastereoselectivity (> 90%), the syn isomers predominantly undergo Norrish Type II elimination. The differences in the product profiles of the diastereomers are consistent with a mechanistic picture involving the formation of precursor diastereomeric triplet 1,4-biradicals in which the substituents at α and β-positions stabilize the cisoid (cyclization) or transoid (elimination) geometry. The fact that such a diastereomeric relationship does indeed ensue at the triplet-excited-state itself is demonstrated via the nanosecond laser-flash photolysis of model ketones 1. The diastereomeric discrimination in the product profiles observed for ketones 2 and 3 as well as in the triplet lifetimes observed for ketones 1 can both be mechanistically traced back to different conformational preferences of the ground-state diastereomeric ketones and the intermediary 1,4-biradicals. Additionally, it emerges from the present study that the syn and anti diastereomers of ketones 2 and 3 represent two extremes of a broad range of widely examined butyrophenones, which lead to varying degrees of Yang photocyclization depending on the alkyl substitution pattern.
- Singhal, Nidhi,Koner, Apurba L.,Mal, Prasenjit,Venugopalan, Paloth,Nau, Werner M.,Moorthy, Jarugu Narasimha
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- Mechanism of Base-Catalyzed Reactions in Phase-Transfer-Systems with Poly(ethylene glycols) as Catalysts. The Isomerization of Allylanisole
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The mechanism of base-catalyzed reactions with poly(ethylene glycol) (PEG) as phase-transfer catalysts was studied by using the isomerization of allylanisole as a model reaction.The reaction kinetics showed the reaction to be chemical reaction controlled.The reaction system was a three-phase system consisting of an organic solvent phase, a PEG-potassium hydroxide complex phase, and a basic aqueous phase.The reaction mechanism included diffusion of the substrate from the solvent to the complex phase reaction and back diffusion of the product.The concentration of theaqueous phase is also important.When the aqueous phase is unsaturated there is no reaction.Concentrations above saturation increase rate because the basic complex becomes more potent under anhydrous conditions.The chain length and chain end moiety of the PEG catalysts have significant influence on the reaction rate.In general, short chain catalysts were more effective per gram but not per mole of catalyst.Etherification of the terminal hydroxyl group reduced activity.When alkoxide species were used as bases the trends were reversed, long chain catalysts being more effective and etherification increasing activity.
- Neumann, Ronny,Sasson, Yoel
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- Synthesis, characterization and in vitro biological evaluation of [Ru(η6-arene)(N,N)Cl]PF6 compounds using the natural products arenes methylisoeugenol and anethole
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Abstract Five new organometallic Ru(II) compounds (VI-X) with the general formula [Ru(η6-arene)(N,N)Cl]PF6, where arene-N,N correspond to methylisoeugenol-bipyridine (VI); anethole-bipyridine (VII); methylisoeugenol-ethylenediamine (VIII); anethole-ethylenediamine (IX) and methylisoeugenol-1,2-diaminobenzene (X), have been synthesized, fully characterized and biologically evaluated in vitro. The reaction conditions based on the reduction of [Ru(1,5-COD)Cl2]n in situ with methyleugenol and estragole, which are natural ligands, induced an alkene isomerization on the allylic substituent of coordinated arenes. The Ru(II)-arene bond formation and isomerization of the CC bond on the allyl substituent was confirmed using 1H NMR spectroscopy; this result was validated for compound VIII by X-ray diffraction. An XRD analysis revealed the presence of both enantiomers of the complex in the single-crystal. Compounds IX and X exhibited a better cytotoxic activity in vitro than carboplatin, which is a commercial drug, against three human tumor cell lines (MCF-7, PC-3 and HT-29).
- Delgado, Ricardo A.,Galdámez, Antonio,Villena, Joan,Reveco, Patricio G.,Thomet, Franz A.
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- Phospholes as efficient ancillaries for the rhodium-catalyzed hydroformylation and hydroaminomethylation of estragole
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The hydroaminomethylation (HAM) of estragole, a bio-renewable starting material, with di-n-butylamine was studied for the first time resulting in three novel amines. The process consists of the alkene hydroformylation followed by the in situ reductive amination of primarily formed aldehydes. In order to control chemo- and regioselectivities, three classes of phosphorus(III) compounds were employed as ancillaries for rhodium(I) catalysts: phosphine, phosphites and phospholes. Phosphole-promoted systems have showed the best overall performance, being more selective in the hydrofomylation step than non-promoted or phosphite-promoted systems, as well as more efficient in the reductive amination step than the standard triphenylphosphine based system. It has been found that both the double bond isomerization (a concurrent reaction) and the enamine hydrogenation (the last step in the HAM process) are favored by less electron-donating ligands, with phospholes presenting an excellent compromise to ensure high chemoselectivity and reasonably fast formation of target amines.
- Oliveira, Kelley C.B.,Carvalho, Sabrina N.,Duarte, Matheus F.,Gusevskaya, Elena V.,Dos Santos, Eduardo N.,Karroumi, Jamal El,Gouygou, Maryse,Urrutigo?ty, Martine
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- Catalyst Decomposition during Olefin Metathesis Yields Isomerization-Active Ruthenium Nanoparticles
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The second-generation Grubbs catalyst, RuCl2(H2IMes)(PCy3) (=CHPh) [GII; H2IMes=1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene, Cy=cyclohexyl], is shown to decompose during olefin metathesis to gen
- Higman, Carolyn S.,Lanterna, Anabel E.,Marin, M. Luisa,Scaiano, Juan C.,Fogg, Deryn E.
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- Isomerization during olefin metathesis: An assessment of potential catalyst culprits
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Two ruthenium hydride complexes commonly proposed as agents of unintended isomerization during olefin metathesis are examined for their activity in isomerization of estragole, a representative allylbenzene. Neither proves kinetically competent to account for the levels of isomerization observed during cross-metathesis of estragole by the second-generation Grubbs catalyst. A structure-activity analysis of selected ruthenium hydride complexes indicates that higher isomerization activity correlates with a more electrophilic metal center. It wasn't me: Two Ru hydrides thought to trigger double-bond migration during olefin metathesis are examined for their isomerization activity. Neither can account for the high levels of undesired isomerization seen during self-metathesis of estragole, a model allylbenzene substrate. Higher activity is found to correlate with a less electron-rich Ru center. Copyright
- Higman, Carolyn S.,Plais, Lucie,Fogg, Deryn E.
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- Support Functionalization with a Phosphine-Containing Hyperbranched Polymer: A Strategy to Enhance Phosphine Grafting and Metal Loading in a Hydroformylation Catalyst
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We present the design of a hydroformylation catalyst through the immobilization of air-stable Rh nanoparticles (NPs) on a magnetic support functionalized with a hyperbranched polymer that bears terminal phosphine groups. The catalyst modification with the hyperbranched polymer improved the metal–support interaction, the metal loading, and the catalytic activity. The catalyst was active for the hydroformylation of natural products, such as estragole, and could be used in successive reactions with negligible metal leaching. The phosphine grafting played a key role in the recyclability of Rh NPs under hydroformylation conditions. The catalytic activity was maintained in successive reactions, even if the catalyst was exposed to air during each recovery procedure. The modification of the support with hyperbranched polyester allowed us either to increase the number of Rh active species or to obtain more active Rh species on the catalyst surface.
- Garcia, Marco A. S.,Heyder, Rodrigo S.,Oliveira, Kelley C. B.,Costa, Jean C. S.,Corio, Paola,Gusevskaya, Elena V.,dos Santos, Eduardo N.,Bazito, Reinaldo C.,Rossi, Liane M.
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- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
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We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
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p. 13337 - 13347
(2021/11/20)
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- Facile Synthesis of Chiral Arylamines, Alkylamines and Amides by Enantioselective NiH-Catalyzed Hydroamination
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Regio- and enantioselective hydroarylamination, hydroalkylamination and hydroamidation of styrenes have been developed by NiH catalysis with a simple bioxazoline ligand under mild conditions. A wide range of enantioenriched benzylic arylamines, alkylamines and amides can be easily accessed by nitroarenes, hydroxylamines and dioxazolones, respectively as amination reagents. The chiral induction in these reactions is proposed to proceed through an enantiodifferentiating syn-hydronickellation step.
- Meng, Lingpu,Yang, Jingjie,Duan, Mei,Wang, You,Zhu, Shaolin
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supporting information
p. 23584 - 23589
(2021/09/28)
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- Spicing up olefin cross metathesis with the renewables estragole and methyl sorbate
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Diene moieties conjugated to a carbonyl group are ubiquitous in nature and are present in compounds with relevant biological properties. Herein we investigate the cross metathesis (CM) of the renewable cross partners estragole and methyl sorbate (MeSo) to produce methyl 6-(4-methoxyphenyl)hexa-2,4-dienoate. By the judicious choice of the ruthenium-based metathesis catalysts, as well as the reaction conditions, it was possible to obtain good conversion and selectivity for the desired product in catalyst loadings as low as 50 ppm (0.005 mol%), with a minimal amount of solvent.
- Ferreira, Leonildo A.,Silva, Josiane T.,Alves, Raissa G.,Oliveira, Kelley C.B.,dos Santos, Eduardo N.
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- Ni-Catalyzed hydrocyanation of alkenes with formamide as the cyano source
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CN generation from formamide dehydration! A novel Ni-catalyzed hydrocyanation of various alkenes to provide aliphatic nitriles is developed by generating hydrocyanic acid in situ from safe and readily available formamide. Excellent linear or branched regio-selectivity, wide substrate scope, cheap and stable nickel salt as a pre-catalyst, a safe cyano source, slow generation of CN to obviate catalyst deactivation and convenient experimental operation would render this hydrocyanation attactive for laboratory synthesis of aliphatic nitriles.
- Shu, Xiao,Jiang, Yuan-Yuan,Kang, Lei,Yang, Luo
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supporting information
p. 2734 - 2738
(2020/06/17)
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- Oxidative [4+2] Cycloaddition of α-(N-Arylamino) Carbonyls with Aryl Alkenes by Multiple C-H Functionalizations and [1,2]-Aryl Shifts
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A new, general copper-catalyzed oxidative tandem [4+2] cycloaddition of α-(N-arylamino) carbonyl compounds with aryl alkenes to produce highly substituted quinolines has been developed, which allows the formation of three new C-C bonds through a sequence of multiple C-H functionalizations, annulation, and [1,2]-aryl shifts.
- Wei, Wen-Ting,Teng, Fan,Li, Yang,Song, Ren-Jie,Li, Jin-Heng
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supporting information
p. 6285 - 6288
(2019/09/06)
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- Stereoselective Synthesis of 1-Arylpropan-2-amines from Allylbenzenes through a Wacker-Tsuji Oxidation-Biotransamination Sequential Process
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Herein, a sequential and selective chemoenzymatic approach is described involving the metal-catalysed Wacker-Tsuji oxidation of allylbenzenes followed by the amine transaminase-catalysed biotransamination of the resulting 1-arylpropan-2-ones. Thus, a series of nine optically active 1-arylpropan-2-amines were obtained with good to very high conversions (74–92%) and excellent selectivities (>99% enantiomeric excess) in aqueous medium. The Wacker-Tsuji reaction has been exhaustively optimised searching for compatible conditions with the biotransamination experiments, using palladium(II) complexes as catalysts and iron(III) salts as terminal oxidants in aqueous media. The compatibility of palladium/iron systems for the chemical oxidation with commercially available and made in house amine transaminases was analysed, finding ideal conditions for the development of a general and stereoselective cascade sequence. Depending on the selectivity displayed by selected amine transaminase, it was possible to produce both 1-arylpropan-2-amines enantiomers under mild reaction conditions, compounds that present therapeutic properties or can be employed as synthetic intermediates of chiral drugs from the amphetamine family. (Figure presented.).
- González-Martínez, Daniel,Gotor, Vicente,Gotor-Fernández, Vicente
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p. 2582 - 2593
(2019/05/15)
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- Preferential Photoreaction in a Porous Crystal, Metal-Macrocycle Framework: PdII-Mediated Olefin Migration over [2+2] Cycloaddition
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A nanosized confined space with well-defined functional surfaces has great potential to control the efficiency and selectivity of catalytic reactions. Herein we report that a 1,6-diene, which normally forms an intramolecular [2+2] cycloadduct under photoirradiation, preferentially undergoes a photoinduced olefin migration in a porous crystal, metal-macrocycle framework (MMF), and alternatively [2+2] cycloaddition is completely inhibited in the confined space. A plausible reaction mechanism for olefin migration triggered by the photoinduced dissociation of the Pd-Cl bond is suggested based on UV-vis diffuse reflectance spectroscopy, single-crystal XRD, and MS-CASPT2 calculation. The substrate scope of the photoinduced olefin migration in MMF was also examined using substituted allylbenzene derivatives.
- Yonezawa, Hirotaka,Tashiro, Shohei,Shiraogawa, Takafumi,Ehara, Masahiro,Shimada, Rintaro,Ozawa, Takeaki,Shionoya, Mitsuhiko
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supporting information
p. 16610 - 16614
(2018/12/11)
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- A Dual-Functional Catalyst for Cascade Meerwein–Pondorf–Verley Reduction and Dehydration of 4″-Methoxypropiophenone to Anethole
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Anethole is an ingredient in many flavours, fragrances and pharmaceutical formulations. To reduce the dependence of its supply on natural oils, a green route for anethole synthesis was designed on the basis of Meerwein–Pondorf–Verley (MPV) reduction and dehydration of 4′-methoxypropiophenone. The one-pot cascade reactions were heterogeneously catalysed by dual-functional Zr-MSU-3, a predominantly Lewis-acidic catalyst with a Si/Zr ratio of 10 and pores with sizes in the range of 3.2–4.2 nm. The use of 2-pentanol as solvent and hydrogen donor for the MPV reduction was advantageous, as its high boiling point enhances the rate of the reactions, especially the dehydration of the MPV product, 1-(4-methoxyphenyl)-propan-1-ol. This dispenses with the need for a strong acid catalyst that could result in by-products of acid-catalysed reactions. Anethole yields of 91 % with a trans/cis isomer ratio of about 92:8, similar to that of natural anethole, were obtained. In comparison, microporous Zr-beta (Si/Zr 12.5) gave lower activity owing to pore-size constraints. Hence, through design of the reactions and catalyst, 4′-methoxypropiophenone can be efficiently converted to anethole in a sustainable and green manner.
- Zhang, Hongwei,Lim, Candy Li-Fen,Zaki, Muhammad,Jaenicke, Stephan,Chuah, Gaik Khuan
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p. 3007 - 3017
(2018/08/03)
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- Synthesis method of aryl olefin
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The invention discloses a synthesis method of aryl-containing substituted olefin. The method is characterized in that aliphatic acetal is used as an alkylating agent to react with an aromatic compound; under the catalysis effect of a solid acid catalyst; at ordinary pressure or low pressure being 0.1 to 1.0MPa and at reaction temperature in the range being 90 to 160 DEG C, one-pot reaction is performed to directly obtain aryl substituted olefin such as anise camphor. The synthesis method has the following characteristics that (1) the synthesis method belongs to a novel synthesis route; the reaction is completed through one pot; (2) the aromatic compound is used as a reactant and is also used as a solvent; other organic solvents are not used; (3) the catalyst is solid acid such as a H-Betamolecular sieve and a metal ion modified molecular sieve; the catalytic amount of catalyst is used; (4) after produced alcohol is recovered, the alcohol can be cyclically used during the acetal synthesis; (5) the reaction can be intermittently performed, and can also be performed in a tubular reactor and a fixed bed reactor; (6) the aftertreatment is simple; no waste is generated in the reaction process; the synthesis method is a green and environment-friendly synthesis route.
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Paragraph 0031; 0032
(2018/05/16)
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- Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
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The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
- Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
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supporting information
p. 6545 - 6555
(2018/06/06)
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- Chemo- and regioselective reductive transposition of allylic alcohol derivatives via iridium or rhodium catalysis
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We report highly chemo- and regioselective reductive transpositions of methyl carbonates to furnish olefin products with complementary regioselectivity to that of established Pd-catalysis. These Rh- and Ir-catalysed transformations proceed under mild conditions and enable selective deoxygenation in the presence of functional groups that are susceptible to reduction by metal hydrides.
- Lundgren, Rylan J.,Thomas, Bryce N.
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p. 958 - 961
(2016/01/20)
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- Direct organocatalytic oxo-metathesis, a trans-selective carbocation-catalyzed olefination of aldehydes
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A direct organocatalytic carbonyl/olefin oxo-metathesis has been developed. The reaction is catalyzed by trityl tetrafluoroborate (TrBF4) and utilizes unactivated alkenes for the olefination of aromatic aldehydes to give trans β-alkylstyrenes in yields of 44-85% with only acetone as the byproduct. The pronounced Lewis acidity of the carbocation results in unusual reactivity that is proposed to catalyze a stepwise [2+2] cycloaddition to give an oxetane intermediate. Fragmentation of the latter in a formal retro [2+2] reaction gives the oxo-metathesis product.
- Naidu, Veluru Ramesh,Bah, Juho,Franzén, Johan
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supporting information
p. 1834 - 1839
(2015/05/27)
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- Catalytic cyclometallation of allylbenzenes by EtAlCl2 and Mg as new route to synthesis of dibenzyl butane lignans
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The cyclometallation of allylbenzenes (Ar = Ph, 4-MeO-Ph, 3,4-(MeO)2-Ph) with EtAlCl2 (Et2AlCl) and Mg in the presence of Zr and Ti catalysts (Dzhemilev reaction) has been studied. The reaction run with high diastereoselectivity and gives cyclic organoaluminum compounds, which deuterolysis or hydrolysis gave 2R(S), 3R(S)-dibenzyl butanes with yield of 48-69%. The study of catalyst structure effect on the substrate conversion, reaction chemo- and stereoselectivity showed that the best results were obtained in the case of Cp2ZrCl2 among the tested complexes. The enantioselectivity of neomenthylindenyl or neomenthyltetrahydroindenyl zirconium catalysts in the reaction did not exceed 20%ee. The trans-configuration of the substitutes in the metallacycles formed in the reaction has been proved by X-ray analysis of the hydrolysis product - 2R(S), 3R(S)-dimethyl-1,4-bis[(4′- methoxyphenyl)methyl]-butane. The proposed method could be used for the one-pot diastereoselective synthesis of dibenzyl butane lignans from readily available allylbenzenes.
- Parfenova, Lyudmila V.,Berestova, Tatyana V.,Kovyazin, Pavel V.,Yakupov, Aydar R.,Mesheryakova, Ekaterina S.,Khalilov, Leonard M.,Dzhemilev, Usein M.
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p. 292 - 298
(2015/02/19)
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- A synergic blend of newly isolated pseudomonas mandelii KJLPB5 and [hmim]Br for chemoselective 2° aryl alcohol oxidation in H2O2: Synthesis of aryl ketone or aldehydes via sequential dehydration-oxidative C=C cleavage
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Pseudomonas mandelii KJLPB5 is reported for the oxidation of aryl alcohols in ionic liquid [hmim]Br (1-hexyl-3-methyl imidazolium bromide) with H 2O2. With a slight alteration of reaction conditions, the developed protocol leads either to (i) chemoselective oxidation of 2° aryl alcohols over 1° and aliphatic counterparts or (ii) direct one pot-two step sequential conversion of 2° aryl alcohols into corresponding one or two carbons shorter aryl aldehydes through oxidative cleavage pathway, thus providing a new facet to metal-free oxidations. The key operational parameters such as substrate concentration, incubation temperature, incubation time, ionic liquid type and ionic liquid concentration are also optimized. Graphical Abstract: [Figure not available: see fulltext.]
- Sharma, Nandini,Sharma, Upendra K.,Salwan, Richa,Kasana, Ramesh C.,Sinha, Arun K.
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scheme or table
p. 616 - 622
(2012/01/14)
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- Cross-coupling of aryl/alkenyl ethers with aryl grignard reagents through nickel-catalyzed C-O activation
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The formation of a C-C bond has been achieved through the cleavage of the sp2 C-O bond of aryl/alkenyl ethers catalyzed by a nickel complex, and by using Grignard reagents as nucleophiles (see scheme). This method displays a broad substrate scope and leads to good to excellent yields of the aryl-aryl or alkenyl-aryl cross-coupling products.
- Xie, Lan-Gui,Wang, Zhong-Xia
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supporting information; experimental part
p. 4972 - 4975
(2011/06/17)
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- Practical iron-catalyzed allylations of aryl grignard reagents
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An operationally simple iron-catalyzed reductive cross-coupling reaction between aryl halides and allyl electrophiles has been developed. The underlying domino process exhibits high versatility with respect to the allylic leaving group (acetate, tosylate, diethyl phosphate, methyl carbonate, trimethylsilanolate, methanethiolate, chloride, bromide) and high economic and environmental sustainability with respect to the catalyst system (0.2-5 mol% tris(acetylacetonato)iron(III), ligand-free) and reaction conditions (tetrahydrofuran, 0°C, 45 min).
- Mayer, Matthias,Czaplik, Waldemar M.,Von Wangelin, Axel Jacobi
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supporting information; experimental part
p. 2147 - 2152
(2010/12/18)
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- Facile construction of highly functionalized 2-pyrrolines via FeCl 3-catalyzed reaction of aziridines with arylalkynes
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A series of highly functionalized 2-pyrrolines have been constructed by using a novel FeCl3-catalyzed reaction of aziridines with arylalkynes, in which an aryl-substituted alkenyl cation is involved.
- Fan, Jinmin,Gao, Linfeng,Wang, Zhiyong
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supporting information; scheme or table
p. 5021 - 5023
(2010/01/06)
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- CATALYSTS FOR ALKENE ISOMERIZATION AND CONJUGATING DOUBLE BONDS IN POLYUNSATURATED FATS AND OILS
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The invention provides ruthenium-comprising catalysts, and methods of making and using them, for conjugating double bonds in polyunsaturated hydrocarbons, including polyunsaturated fatty acid derivatives, such as natural fats and oils which comprise (contain) more than one carbon to carbon double bond - where the double bonds are separated by, e.g., a methylene, ethylene or propylene or longer group. The invention provides compositions and methods for treating fats and oils comprising "interrupted" (e.g., "methylene-, ethylene- or propylene- interrupted") double bonds to generate isomers with "conjugated" double bonds. The invention also provides compositions, and methods of making and using them, for making catalysts on a solid support. In one aspect, these catalysts are for alkene isomerization or exchange of alkene hydrogens for other isotopes. The invention provides heterocyclic resin-based compositions, and methods of using them, for making catalysts for alkene isomerization and exchange of hydrogens for deuterium or tritium isotopes.
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Page/Page column 27-28
(2009/03/07)
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- Palladium-catalyzed cross-coupling of aryl chlorides with alkenylboronic acids with low E/Z isomerization
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Using a bulky electron-rich monodentate benzoferrocenyl phosphine as supporting ligand, an efficient protocol for stereoselective palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl chlorides with alkenylboronic acids was uncovered. Using this protocol, both trans- and cis-alkenylboronic acids can be coupled with high stereoselectivity giving the corresponding vinylarenes in good to quantitative yields. Electron-poor and -rich aryl chlorides including highly hindered ones are all suitable substrates for the reaction.
- Thimmaiah, Muralidhara,Zhang, Xiang,Fang, Shiyue
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p. 5605 - 5607
(2008/12/22)
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- Synthesis of a new 1,4-aminoalcohol and its use as catalyst in the enantioselective addition of organozinc to aldehydes
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The synthesis of a new enantiopure, conformationally constrained 1,4-aminoalcohol is reported, starting from commercially available reagents from the chiral pool. This 1,4-aminoalcohol was used as chiral ligand in the addition of Et2Zn to aldehydes (best ee 98%) and in the synthesis of chiral propargylic alcohols (best ee 70%) by alkynylzinc species.
- Scarpi, Dina,Galbo, Fabrizio Lo,Guarna, Antonio
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p. 1409 - 1414
(2007/10/03)
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- Stereoselective hydrothiolation of alkynes catalyzed by cesium base: Facile access to (Z)-1-alkenyl sulfides
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Treatment of alkyne with alkanethiol in the presence of a catalytic amount of cesium carbonate and a radical inhibitor in DMSO provides the corresponding adduct, (Z)-1-alkenyl alkyl sulfide, in good yield with high selectivity.
- Kondoh, Azusa,Takami, Kazuaki,Yorimitsu, Hideki,Oshima, Koichiro
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p. 6468 - 6473
(2007/10/03)
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- Pd2(dba)3/P(i-BuNCH2CH2) 3N-catalyzed Stille cross-coupling of aryl chlorides
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The Pd2(dba)3/P(i-BuNCH2CH 2)3N (1d) catalyst system is highly effective for the Stille cross-coupling of aryl chlorides with organotin compounds. This method represents only the second general method for the coupling of aryl chlorides. Other proazaphosphatranes possessing benzyl substituents also generate very active catalysts for Stille reactions. Noteworthy features of the method are: (a) commercial availability of ligand 1d, (b) the wide array of aryl chlorides that can be coupled, and (c) applicability to aryl, vinyl, and allyl tin reagents.
- Su, Weiping,Urgaonkar, Sameer,Verkade, John G.
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p. 1421 - 1424
(2007/10/03)
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- Highly active palladium catalysts supported by bulky proazaphosphatrane ligands for stille cross-coupling: Coupling of aryl and vinyl chlorides, room temperature coupling of aryl bromides, coupling of aryl triflates, and synthesis of sterically hindered biaryls
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A family of proazaphosphatrane ligands [P(RNCH2CH 2)2N(R′NCH2CH2): R = R′ = i-Bu, 1; R = Bz, R′ = 1-Bu, 3; R = R′ = Bz, 4] for palladium-catalyzed Stille reactions of aryl chlorides is described. Catalysts derived from ligands 1 and 4 efficiently catalyze the coupling of electronically diverse aryl chlorides with an array of organotin reagents. The catalyst system based on the ligand 3 is active for the synthesis of sterically hindered biaryls (di-, tri-, and tetra-ortho substituted). The use of ligand 4 allows room-temperature coupling of aryl bromides and it also permits aryl inflates and vinyl chlorides to participate in Stille coupling.
- Su, Weiping,Urgaonkar, Sameer,McLaughlin, Patrick A.,Verkade, John G.
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p. 16433 - 16439
(2007/10/03)
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- Nickel catalyzed cross-coupling of modified alkyl and alkenyl Grignard reagents with aryl- and heteroaryl nitriles: Activation of the C-CN bond
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The nickel catalyzed cross-coupling of alkyl and alkenyl Grignard reagents with aryl nitrile derivatives affords good yields of the corresponding aryl alkanes or aryl alkenes via activation of the C-CN bond. To prevent direct addition of the nucleophile to the nitrile group, the reactivity of the Grignard reagent was modulated by reaction with either LiOt-Bu or PhSLi prior to cross-coupling. The optimum catalyst was determined to be NiCl2(PMe3)2, which is a convenient air stable commercially available complex.
- Miller, Joseph A.,Dankwardt, John W.
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p. 1907 - 1910
(2007/10/03)
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- Cobalt-catalyzed alkenylation of organomagnesium reagents
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Alkenyl iodides, bromides and chlorides react with organomagnesium reagents in THF, in the presence of Co(acac)2 and NMP (9 to 4 equiv.), to give the cross-coupling products in good yields. The reaction is chemoselective (aryl or alkyl bromides, esters and ketones) and stereoselective (≤ 99.5%).
- Cahiez, Gerard,Avedissian, Hovsep
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p. 6159 - 6162
(2007/10/03)
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- Nickel-catalyzed direct electrochemical cross-coupling between aryl halides and activated alkyl halides
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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
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p. 1748 - 1755
(2007/10/03)
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- The Stereochemistry of Rearrangements of Aryl and Hetaryl Groups to Primary Carbenic Centers
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The products and stereochemistries of carbenic decompositions of varied 2-aryl-1-diazoalkanes and 1-diazo-2-(2-hetaryl)propanes have been determined.
- Slack, W. E.,Taylor, W.,Moseley, C. G.,Chang, K. T.,Kraska, A.,et al.
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p. 2647 - 2650
(2007/10/02)
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- Untersuchungen im Wittig-System nach einem ordnenden Konzept auf der Basis alternativer Prinzipien
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Our results show that the stereoselectivity of the Wittig-reaction can be controlled by the variation of substituents in accord with the ORDERING CONCEPT OF ALTERNATIV PRINCIPLES (individual pairs, known and unknown classes of alternatives).The "all-phenyl Wittig-system" having three phenyl groups on phosphorous two in ylid- and aldehyd-position was chosen as a standard for our investigations.Differentiation in ylid-position and compensation on phosphorous and aldehyd-position were observed by the comparison of "patterns".Consequently, most of the selectivity rules of Wittig-reactions can be explained by the differentiation through alternatives in the ylid-position.Inversion or conservation of the "patterns" of measured data points to the variation in structure of starting materials, reaction rates and selectivities.Amount-controls were also described in certain systems.
- Bandmann, Heinz,Bartik, Tamas,Bauckloh, Sylvia,Behler, Ansgar,Brille, Frank,et al.
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p. 193 - 204
(2007/10/02)
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- ANOMALOUS BEHAVIOR OF SUBSTITUTED ALLYL BENZENES IN PALLADIUM(II) CATALYSED REACTION
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The Wacker reaction is one of the finest examples of transition metal promoted nucleophilic addition to olefins.An unusual observation has been made with reagard to the normal Wacker process, whereby, the oxidation of eugenol (1) and methyl chavicol (2) does not lead to their respective carbonyl compounds.The reactions leading to the formation of two novel products and their mechanistic aspects are discussed.
- Iyer, Meera,Rele, Dinesh N.,Trivedi, G. K.
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p. 759 - 762
(2007/10/02)
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- β-Cyclodextrin as a reverse phase transfer catalyst in the isomerization of 4-allyl anisole
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β-Cyclodextrin accelerates the IrCl3x3H2O catalyzed isomerization of 4-allyl anisole via a reverse phase transfer mechanism.
- Barak, Gabriela,Sasson, Yoel
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- Kinetic Determination of Selectivity Constants of Anion Extraction in Phase-transfer Catalytic Systems
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A kinetic method has been developed to measure selectivity constants af pair of anions in phase-transfer catalytic systems.The method is based on the study of the poisoning effect produced by the presence of catalytic amounts of different salts in the kinetic behaviour of the phase-transfer-catalysed isomerisation of 4-allylanisole to 4-methoxy-β-methylstyrene in basic medium.The kinetic profiles experimentally obtained for this reaction are numerically analysed and Ksel values for different anions are subsequently derived.Particular attention is given to alkoxide anions, formed in situ by contact of alcohols with concentrated NaOH.A selectivity constant parameter that includes the acidity of the alcohols is defined.
- Zerda, Jaime de la,Sasson, Yoel
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p. 1147 - 1152
(2007/10/02)
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- Hofmann Decomposition of Queternary Ammonium Salts under Phase-transfer Catalytic Conditions
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The known Hofmann degradation of quaternary ammonium salts under basic phase-transfer catalytic conditions has been studied.The base-catalysed isomerization of p-allylanisole to p-methoxy-β-methylstyrene was used as a kinetic probe to find experimentally the rate constant and activation energy of the Hofmann decomposition without isolating the quaternary ammonium basic salt R4N+B- (B- = base anion).Reactions performed at various temperatures showed that the higher the temperature the greater was the initial rate but the lower the final conversion in the isomerization reaction.The quaternary ammonium hydroxide was found to catalyse the isomerization and the Hofmann degradation more effectively than the corresponding alkoxide.This indicates that the former is a stronger base in the non-polar aprotic solvents common in phase-transfer catalysis.
- Zerda, Jaime de la,Neumann, Ronny,Sasson, Yoel
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p. 823 - 826
(2007/10/02)
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- Regiochemistry of Nucleophilic Opening of β-Substituted Styrene Oxides with Thiolate Anions: Model Experiments in the Synthesis of Leukotriene Analogues
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β-Substituted trans-styrene oxides are cleaved with thiolate anions highly regioselectively by attack at the α-carbon whereas the cis-isomers are cleaved by attack at the α- and β-carbons.Cysteine, in a suitably protected form, similarly cleaves β-substituted trans-styrene oxides, thus allowing the synthesis of a simple LTE model.
- Marples, Brian A.,Saint, Christopher G.,Traynor, John R.
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p. 567 - 574
(2007/10/02)
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- β-Adrenergic blocking agents. 20. (3-Hydroxyprop-1-enyl)-substituted 1-(aryloxy)-3-(alkylamino)propan-2-ols
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The synthesis of a series (3-hydroxyprop-1-enyl)-substituted 1-(aryloxy)-3-(alkylamino)propan-2-ols is described. These compounds were investigated for their β-adrenoreceptor blocking properties and their selectivity of action. Among the o-(hydroxypropenyl)-substituted derivatives the authors have found some potent noncardioselective β-adrenoreceptor blocking agents which have a greater blocking action on the β2 receptor, thus resembling propanolol. The p-(hydroxypropenyl)-substituted analogues were generally less potent and tended to be cardioselective. The structure-activity relationships are discussed in the light of the hypothesis that the cardioselectivity of p-amido-substituted (aryloxy)propanolamines is attributable, in part, to binding of the amide group to some additional site on the β receptor; these findings argue against a similar interaction for the allylic hydroxyl group.
- Tucker
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p. 1122 - 1126
(2007/10/02)
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