- Selective and Additive-Free Hydrogenation of Nitroarenes Mediated by a DMSO-Tagged Molecular Cobalt Corrole Catalyst
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We report on the first cobalt corrole that effectively mediates the homogeneous hydrogenation of structurally diverse nitroarenes to afford the corresponding amines. The given catalyst is easily assembled prior to use from 4-tert-butylbenzaldehyde and pyrrole followed by metalation of the resulting corrole macrocycle with cobalt(II) acetate. The thus-prepared complex is self-contained in that the hydrogenation protocol is free from the requirement for adding any auxiliary reagent to elicit the catalytic activity of the applied metal complex. Moreover, a containment system is not required for the assembly of the hydrogenation reaction set-up as both the autoclave and the reaction vessels are readily charged under a regular laboratory atmosphere.
- Sch?fberger, Wolfgang,Timelthaler, Daniel,Topf, Christoph
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supporting information
p. 2114 - 2120
(2021/07/22)
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- The ortho effect on the acidic and alkaline hydrolysis of substituted formanilides
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The kinetics of formanilides hydrolysis were determined under first-order conditions in hydrochloric acid (0.01-8 M, 20-60°C) and in hydroxide solutions (0.01-3 M, 25 and 40°C). Under acidic conditions, second-order specific acid catalytic constants were used to construct Hammett plots. The ortho effect was analyzed using the Fujita-Nishioka method. In alkaline solutions, hydrolysis displayed both first- and second-order dependence in the hydroxide concentration. The specific base catalytic constants were used to construct Hammett plots. Ortho effects were evaluated for the first-order dependence on the hydroxide concentration. Formanilide hydrolyzes in acidic solutions by specific acid catalysis, and the kinetic study results were consistent with the AAC2 mechanism. Ortho substitution led to a decrease in the rates of reaction due to steric inhibition of resonance, retardation due to steric bulk, and through space interactions. The primary hydrolytic pathway in alkaline solutions was consistent with a modified BAC2 mechanism. The Hammett plots for hydrolysis of meta- and para-substituted formanilides in 0.10 M sodium hydroxide solutions did not show substituent effects; however, ortho substitution led to a decrease in rate constants proportional to the steric bulk of the substituent.
- Desai, Salil Dileep,Kirsch, Lee E.
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p. 471 - 488
(2015/06/30)
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- Weak halogen bonding in solid haloanilinium halides probed directly via chlorine-35, bromine-81, and iodine-127 NMR spectroscopy
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A series of monohaloanilinium halides exhibiting weak halogen bonding (XB) has been prepared and characterized by 35Cl, 81Br, and 127I solid-state nuclear magnetic resonance (SSNMR) spectroscopy in magnetic fields of up to 21.1 T. The quadrupolar and chemical shift (CS) tensor parameters for halide ions (Cl-, Br-, I-) which act as electron density donors in the halogen bonds of these compounds are measured to provide insight into the possible relationship between halogen bonding and NMR observables. The NMR data for certain series of related compounds are strongly indicative of when such compounds pack in the same space group, thus providing practical structural information. Careful interpretation of the NMR data in the context of novel and previously available X-ray crystallographic data, and new gauge-including projector-augmented-wave density functional theory (GIPAW DFT) calculations has revealed several notable trends. When a series of related compounds pack in the same space group, it has been possible to interpret trends in the NMR data in terms of the strength of the halogen bond. For example, in isostructural series, the halide quadrupolar coupling constant was found to increase as the halogen bond weakens. In the case of a series of haloanilinium bromides, the 81Br isotropic chemical shift and CS tensor span both decrease as the bromide-halogen XB is weakened. These trends were reproduced using both GIPAW DFT and cluster-model calculations of the bromide ion magnetic shielding tensor. Such trends are particularly exciting given the well-known role that NMR has played historically in the characterization of hydrogen bonding.
- Attrell, Robert J.,Widdifield, Cory M.,Korobkov, Ilia,Bryce, David L.
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experimental part
p. 1641 - 1653
(2012/06/30)
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- Kinetics and mechanism of the anilinolysis of dicyclohexyl phosphinic chloride in acetonitrile
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The nucleophilic substitution reactions of dicyclohexyl phosphinic chloride [3; cHex2P(=O)Cl] with substituted anilines (XC6H 4NH2) and deuterated anilines (XC6H 4ND2) are investigated kinetically in acetonitrile at 60.0 °C. The anilinolysis rate is too slow to be rationalized by the stereoelectronic effects. The rate is contrary to expectations for the electronic influence of the two ligands and exhibits exceptionally great negative deviation from the Taft's eq. The deuterium kinetic isotope effects (DKIEs) involving deuterated anilines invariably change from primary normal (kH/kD > 1; max kH/kDt = 1.10 with X = 4-MeO) with the strongly basic anilines (X = 4-MeO, 4-Me, 3-Me) to secondary inverse (kH/kDt H/k Dt = 0.673 with X = 3-Cl) with the weakly basic anilines (X = H, 4-F, 4-Cl, 3-Cl). A concerted SN2 mechanism is proposed on the basis of both secondary inverse and primary normal DKIEs. The obtained DKIEs imply that the fraction of a frontside attack increases as the aniline becomes more basic. A hydrogen-bonded, four-center-type transition state is suggested for a frontside attack, while the trigonal bipyramidal pentacoordinate transition state is suggested for a backside attack.
- Ul Hoque, Md. Ehtesham,Lee, Hai Whang
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experimental part
p. 1997 - 2002
(2012/02/01)
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- Concurrent primary and secondary deuterium kinetic isotope effects in anilinolysis of O-aryl methyl phosphonochloridothioates
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The nucleophilic substitution reactions of Y-O-aryl methyl phosphonochloridothioates with substituted anilines (XC6H 4NH2) and deuterated anilines (XC6H 4ND2) are investigated kinetically in acetonitrile at 55.0°C. The Hammett and Bronsted plots for substituent (X) variations in the nucleophiles are biphasic concave downwards with a break region between X = H and 4-Cl. The deuterium kinetic isotope effects (DKIEs) are primary normal (kH/kD = 1.03-1.30) for stronger nucleophiles (X = 4-MeO, 4-Me and H), and extremely large secondary inverse (kH/kD = 0.367-0.567) for weaker nucleophiles (X = 4-Cl, 3-Cl and 3-NO2). The cross-interaction constants are negative (ρXY(H) = -0.95 and ρXY(D) = -1.11) for stronger nucleophiles, while positive (ρXY(H) = +0.77 and ρXY(D) = +0.21) for weaker nucleophiles. These kinetic results indicate that the mechanism changes from a concerted process involving frontside nucleophilic attack for stronger nucleophiles to a stepwise process with a rate-limiting leaving group expulsion from the intermediate involving backside attack for weaker nucleophiles. A hydrogen-bonded, four-center-type transition state (TS) is suggested for a frontside attack, while a trigonal bipyramidal pentacoordinate TS is suggested for a backside attack. The unusually small DKIEs, as small as or equal to 0.4, for weaker nucleophiles seem to be ascribed to severe steric congestion in the TS.
- Ul Hoque, Md. Ehtesham,Guha, Arun Kanti,Kim, Chan Kyung,Lee, Bon-Su,Lee, Hai Whang
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experimental part
p. 2919 - 2925
(2011/02/28)
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- Kinetics and mechanism of the aminolysis of dimethyl and methyl phenyl phosphinic chlorides with anilines
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The reactions of dimethyl phosphinic chloride (1) and methyl phenyl phosphinic chloride (2) with X-anilines have been studied kinetically in acetonitrile at 15.0 and 55.0 °C, respectively. The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC 6H4ND2) are also reported for the same reactions. The obtained KIEs for 1 are secondary inverse (kH/k D=0.703-0.899H/kD=1.62-2.10> 1). A concerted mechanism involving predominantly backside nucleophilic attack is proposed for the anilinolysis of 1. A concerted mechanism involving predominantly frontside attack via a hydrogen-bonded four-center-type transition state is proposed for the anilinolysis of 2. The degree of steric hindrance is the major factor that determines both the reactivity of the phosphinates and the direction of the nucleophilic attack on the phosphinates. Copyright
- Dey, Nilay Kumar,Hoque, Md. Ehtesham Ul,Kim, Chan Kyung,Lee, Bon-Su,Lee, Hai Whang
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experimental part
p. 425 - 430
(2010/04/30)
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- Pyrimidine derivatives and processes for the preparation thereof
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4-Amino-1H-pyrazolo[3,4-d]pyrimidine derivatives of formula I wherein the substituents are as defined in claim 1, are described.These compounds inhibit the tyrosine kinase activity of the receptor for epidermal growth factor (EGF) and c-erbB2 kinase and can be used as anti-tumor agents.
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- Joint effect of the structure and medium on the rate of reactions of aroyl chlorides with primary arylamines in mixtures of tert-butyl alcohol with chlorobenzene. Isoparametric points with respect to the variable parameters
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The effects of the composition of the medium (3.5, 5, and 7 M solutions of tert-butyl alcohol in chlorobenzene), of pairs of variable factors (the composition of the medium with the structure of the aroyl chlorides and the composition of the medium with the structure of the primary arylamines), and of all three factors together on the rate of the reactions of aroyl chlorides with primary arylamines were determined quantitatively.It was found that the mutual effects of the structure and the medium on the reactivity of the system were nonadditive.It was shown experimentally that there are isoparametric points with respect to the medium, the structure of the substrate, and the structure of the nucleophile, and the transition was made through some of these points.
- Likhomanenko, E. E.,Shpan'ko, I. V.
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p. 139 - 144
(2007/10/02)
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- EFFECT OF THE STRUCTURE ON THE RATE OF THE REACTIONS OF AROYL CHLORIDES WITH PRIMARY ARYLAMINES IN MIXTURES OF tert-BUTYL ALCOHOL AND CHLOROBENZENES. THE TRANSITION THROUGH ISOPARAMETRIC POINTS WITH RESPECT TO THE STRUCTURE PARAMETERS
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The rate of the reactions of aroyl chlorides with primary arylamines in 3.5, 5, and 7M solutions of tert-butyl alcohol in chlorobenzene at 25 deg C was measured.The effect of the structure of the reagents on the process rate was determined quantitatively by means of the Hammett-Taft and crossed correlation equations.The isoparametric points with respect to the structure of the substrate and the nucleophile were reached experimentally, and the transition through some of these points was also realised.It was found that the specific solvation of the primary arylamines by the tert-butyl alcohol was nonuniform in that an incre ase in the concentration of the alcohol in the investigated range reduced, did not change, and increased the rates of the reactions with 3-chloroaniline, 3-nitroaniline, and 3-nitro-5-methoxycarbonylaniline respectively.The effect of specific solvation on the behavior of the correlation parameters is discussed.
- Shpan'ko, I. V.,Likhomanenko, E. E.
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p. 1702 - 1710
(2007/10/02)
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