108-89-4Relevant articles and documents
Structural Effects on the Iodine Cation Basicity of Organic Bases in the Gas Phase
Abboud, Jose-Luis M.,Notario, Rafael,Santos, Lucia,Lopez-Mardomingo, Carmen
, p. 8960 - 8961 (1989)
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SITE OF PROTONATION AND CONFORMATIONAL EFFECTS ON GAS-PHASE BASICITY IN beta -AMINO ALCOHOLS. THE NATURE OF INTERNAL H BONDING IN beta -HYDROXY AMMONIUM IONS.
Houriet,Reufenacht,Carrupt,Vogel,Tichy
, p. 3417 - 3422 (1983)
The influence of interfunctional distance on the gas-phase basicity of beta -amino alcohols is investigated by the method of equilibrium proton-transfer reactions in an ion cyclotron resonance (ICR) spectrometer. It is found that in the protonated species, interaction between the most basic center (amino group) with the hydroxy group results in stabilization of the system. The stabilization energy increases as the interfunctional distance decreases to reach a maximum value of about 7 kcal/mol for coplanar systems. Comparison with the values determined by ab initio calculations indicates that internal H bonding can be described in terms of the ion-dipole potential energy between the ammonium ion and the hydroxy group. External vs. internal ion solvation effects are also discussed.
Two-State Reactivity in Iron-Catalyzed Alkene Isomerization Confers σ-Base Resistance
Lutz, Sean A.,Hickey, Anne K.,Gao, Yafei,Chen, Chun-Hsing,Smith, Jeremy M.
, p. 15527 - 15535 (2020)
A low-coordinate, high spin (S = 3/2) organometallic iron(I) complex is a catalyst for the isomerization of alkenes. A combination of experimental and computational mechanistic studies supports a mechanism in which alkene isomerization occurs by the allyl mechanism. Importantly, while substrate binding occurs on the S = 3/2 surface, oxidative addition to an η1-allyl intermediate only occurs on the S = 1/2 surface. Since this spin state change is only possible when the alkene substrate is bound, the catalyst has high immunity to typical σ-base poisons due to the antibonding interactions of the high spin state.
Oxygenation of hydrocarbons mediated by mixed-valent basic iron trifluoroacetate and valence-separated component species under Gif-type conditions involves carbon- and oxygen-centered radicals
Tapper, Amy E.,Long, Jeffrey R.,Staples, Richard J.,Stavropoulos, Pericles
, p. 2343 - 2346 (2000)
Hydrogen-atom abstraction by hydroxyl radicals takes place to generate both tert- and sec-adamantyl radicals in Gif-type oxygenation of adamantane by H2O2 in pyridine/trifluoroacetic acid when the reaction is mediated by [Fe(O2CCF3)2(py)4] or [Fe2O(O2CCF3)4(py)6], which are formed by dissociation of [Fe3O(O2CCF3)6- (L)3] in pyridine (L = H2O, DMSO; see scheme).
Lozano, Rafael,Roman, Jesus,De Jesus, Fernando,Alarcon, Esteban
, p. 231 - 238 (1991)
A computational, X-ray crystallographic and thermal stability analysis of TETROL and its pyridine and methylpyridine inclusion complexes
Barton, Benita,Caira, Mino R.,Hosten, Eric C.,McCleland, Cedric W.
, p. 8713 - 8723 (2013)
The identification and application of (+)-(2R,3R)-1,1,4,4- tetraphenylbutane-1,2,3,4-tetrol (TETROL) as an efficient and selective host compound is described. Computational and single crystal X-ray diffraction analyses revealed that the butane backbone of TETROL adopts a relatively rigid anti-conformation, with the hydroxy groups oriented syn and connected through a cyclic, homodromic arrangement of their O-H bonds. This structure is stabilised through a pair of 1,3-hydrogen bonding interactions. TETROL forms inclusion complexes with pyridine and 3- and 4-methylpyridine, and does so selectively from mixtures of the pyridines. X-ray diffraction (single crystal and powder) and thermal analyses of the inclusion compounds are described.
Nitrogen kinetic isotope effects on the decarboxylation of 4-pyridylacetic acid
Sicinska,Lewandowicz,Vokal,Paneth
, p. 5534 - 5536 (2001)
Nitrogen kinetic isotope effects on the decarboxylation of 4-pyridylacetic acid have been measured in solvents of different polarity and have been found to vary from the inverse value of 0.994 to the normal value of 1.002 upon increase of water content of
Kinetics and mechanistic study on deoxygenation of pyridine oxide catalyzed by {MeReVO(pdt)} 2 dimer
Ibdah, Abdellatif,Alduwikat, Salwa
, p. 9 - 20 (2017)
The oxorhenium(V) dimer {MeReO(pdt)}2 (where pdt?=?1,2-propanedithiolate) catalyze the oxygen atom transfer (OAT) reaction from the pyridine oxide to triphenylarsine (Ph3As). The rate law is given by ν?=?k[Re-dimer][PyNO] and zero order dependence on Ph3As. The value of k at 25?°C in CHCl3 is 139?±?3?L?mol?1?s?1. The activation parameters are ΔH??=?12.2?±?1.0?kcal?mol?1 and ΔS??=??7.9?±?3.24?cal?K?1?mol?1. According to the proposed mechanism, the rate determining step is the oxidation of ReVO to ReVIIO2 and the pyridine release. The triphenylarsine enters the catalytic cycle after the rate determining step. The reaction constant ρ?=??1.4 obtained from Hammett correlation with σ for different substituted pyridine N-oxide. The computational study indicates that the oxidation of ReV to ReVII and release of the pyridine step is insensitive to the nature of the substituent on the pyridine with the average estimated activation barrier ≈11.5?kcal/mol from six different substituted pyridine oxide. It is proposed that electron donor substituent enrich the equilibrium of the first step of the proposed mechanism which is the coordination of the pyridine oxide with one rhenium atom to form I1 (Scheme 2). The electron donor substituent on the pyridine increase the concentration of I1 which will increase the rate of the reaction as the ν?=?k2[I1].
SYNTHESIS OF METHYLPYRIDINES IN THE PRESENCE OF Pd COMPLEXES CONTAINING S
Chekurovskaya, E. D.,Akimov, A. N.,Vaistub, T. G.,Tarasova, T. M.
, p. 1070 - 1072 (1991)
Synthesis of methylpyridines from acetaldehyde and ammonia in the presence of heterogeneous Pd complexes containing S is studied by a pulsed microcatalytic method.The process occurs with selective formation of 4-methylpyridine.The difference in the catalytic activity of the studied complexes is explained on the basis of 13C NMR spectra.
Polycyclic N-hetero compounds. XIII. Reactions of pyridine N-oxides with formamide
Koyama,Nanba,Hirota,et al.
, p. 964 - 967 (1977)
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Kinetic and Computational Studies of Rhenium Catalysis for Oxygen Atom Transfer Reactions
Ibdah, Abdellatif,Bakar, Heba Bani,Alduwikat, Salwa
, p. 149 - 159 (2018)
The rhenium(v)oxo dimer {MeReO(edt)}2 (edt≤1,2-ethanedithiolate) is an effective catalyst for the oxygen atom transfer (OAT) reaction from pyridine oxide and picoline oxide to triphenylarsine (Ph3As) as oxygen acceptor. Kinetics measurements were carried
Expansion of Azulenes as Nonbenzenoid Aromatic Compounds for C-H Activation: Rhodium- And Iridium-Catalyzed Oxidative Cyclization of Azulene Carboxylic Acids with Alkynes for the Synthesis of Azulenolactones and Benzoazulenes
Maeng, Chanyoung,Son, Jeong-Yu,Lee, Seung Cheol,Baek, Yonghyeon,Um, Kyusik,Han, Sang Hoon,Ko, Gi Hoon,Han, Gi Uk,Lee, Kyungsup,Lee, Kooyeon,Lee, Phil Ho
, p. 3824 - 3837 (2020)
Rhodium-catalyzed oxidative [4 + 2] cyclization reactions through the C-H activation of azulene carboxylic acids as nonbenzenoid aromatic compounds with symmetrical and unsymmetrical alkynes were developed under aerobic conditions, which produced azulenolactone derivatives with a wide substrate scope and excellent functional group tolerance. Interestingly, azulenic acids in reaction with alkynes underwent iridium-catalyzed [2 + 2 + 2] cyclization accompanied by decarboxylation to afford tetra(aryl)-substituted benzoazulene derivatives. The reactivity order for C-H activation reaction is greater toward azulene-6-carboxylic acid, azulene-1-carboxylic acid, and azulene-2-carboxylic acid. For the first time, the expansion of azulenes having directing group as nonbenzenoid aromatic compounds for C-H activation was successful, indicating that nonbenzenoid aromatic compounds can be used as good substrates for the C-H activation reaction. Therefore, the research area of C-H activation will certainly expand to nonbenzenoid aromatic compounds in future.
Nonclassical oxygen atom transfer reactions of oxomolybdenum(vi) bis(catecholate)
Marshall-Roth, Travis,Liebscher, Sean C.,Rickert, Karl,Seewald, Nicholas J.,Oliver, Allen G.,Brown, Seth N.
, p. 7826 - 7828 (2012)
Mechanistic studies indicate that the oxomolybdenum(vi) bis(3,5-di-tert-butylcatecholate) fragment deoxygenates pyridine-N-oxides in a reaction where the oxygen is delivered to molybdenum but the electrons for substrate reduction are drawn from the bound catecholate ligands, forming 3,5-di-tert-butyl-1,2-benzoquinone.
Synthesis of Pyridine Bases over Ion-exchanged Pentasil Zeolite
Sato, Hiroshi,Shimizu, Shinkichi,Abe, Nobuyuki,Hirose, Ken-ichi
, p. 59 - 62 (1994)
The catalytic activity of pentasil zeolite for the synthesis of pyridine bases from aldehydes and ammonia was found to depend upon the Si/Al ratio and the metal cation.The best choices are 30 to 120 of Si/Al ratios and metal cations Such as Tl(I), Pb(II), Co(II) and Zn(II).
Basicity of pyridine and some substituted pyridines in ionic liquids
Angelini, Guido,De Maria, Paolo,Chiappe, Cinzia,Fontana, Antonella,Pierini, Marco,Siani, Gabriella
, p. 3912 - 3915 (2010)
Figure presented The equilibrium constants for ion pair formation of some pyridines have been evaluated by spectrophotometric titration with trifluoroacetic acid in different ionic liquids. The basicity order is the same in ionic liquids and in water. The substituent effect on the equilibrium constant has been discussed in terms of the Hammett equation. Pyridine basicity appears to be less sensitive to the substituent effect in ionic liquids than in water.
Solvent dependence of oxygen isotope effects on the decarboxylation of 4-pyridylacetic acid
Headley, George W.,O'Leary, Marion H.
, p. 1894 - 1896 (1990)
Oxygen isotope effects on the decarboxylation of 4-pyridylacetic acid have been measured by the remote-label technique. The isotope effect varies from k16/k18 = 0.995 per oxygen in 25% dioxane to 1.003 in 75% dioxane. The isotope effect reflects three contributions: An inverse isotope effect of 0.98-0.99 due to the change in carbon-oxygen bond order on going from ground state to transition state, an effect of 1.01-1.02 due to desolvation of the carboxyl group, and an effect of approximately 1.01 due to the acid-base equilibrium of the carboxyl group. Thus, oxygen isotope effects on decarboxylation should be a useful probe for carboxyl desolvation in enzymatic decarboxylations.
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Akhemerov et al.
, (1975)
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Activation of rhenium(I) toward substitution in fac -[Re(N,O′ -Bid)(CO)3(HOCH3)] by Schiff-base bidentate ligands (N,O′ -Bid)
Brink, Alice,Visser, Hendrik G.,Roodt, Andreas
, p. 8950 - 8961 (2013)
A series of fac-[Re(N,O′-Bid)(CO)3(L)] (N,O′-Bid = monoanionic bidentate Schiff-base ligands with N,O donor atoms; L = neutral monodentate ligand) has been synthesized, and the methanol substitution reactions have been investigated. The complexes were characterized by NMR, IR, and UV-vis spectroscopy. X-ray crystal structures of the compounds fac-[Re(Sal-mTol)(CO)3(HOCH3)], fac-[Re(Sal-pTol)(CO) 3(HOCH3)], fac-[Re(Sal-Ph)(CO)3(HOCH 3)], and fac-[Re(Sal-Ph)(CO)3(Py)] (Sal-mTol = 2-(m-tolyliminomethyl)phenolato; Sal-pTol = 2-(p-tolyliminomethyl)phenolato; Sal-Ph = 2-(phenyliminomethyl)phenolato; Py = pyridine) are reported. Significant activation for the methanol substitution is induced by the use of the N,O bidentate ligand as manifested by the second order rate constants, with limiting kinetics being observed for the first time. Rate constants (25 C) (k1 or k3) and activation parameters (ΔH ka, kJ mol-1; ΔS ka, J K-1 mol-1) from Eyring plots for entering nucleophiles as indicated are as follows: fac-[Re(Sal-mTol)(CO)3(HOCH3)] 3-chloropyridine: (k 1) 2.33 ± 0.01 M-1 s-1; 85.1 ± 0.6, 48 ± 2; fac-[Re(Sal-mTol)(CO)3(HOCH3)] pyridine: (k1) 1.29 ± 0.02 M-1 s-1; 92 ± 2, 66 ± 7; fac-[Re(Sal-mTol)(CO)3(HOCH3)] 4-picoline: (k1) 1.27 ± 0.05 M-1 s-1; 88 ± 2, 53 ± 6; (k3) 3.9 ± 0.03 s-1; 78 ± 8, 30 ± 27; (kf) 1.7 ± 0.02 M-1 s-1; 86 ± 2, 49 ± 6; fac-[Re(Sal-mTol)(CO) 3(HOCH3)] DMAP (k3) 1.15 ± 0.02 s -1; 88 ± 2, 52 ± 7. An interchange dissociative mechanism is proposed.
1,4-dioxobenzene compounds of gallium: Reversible binding of pyridines to [{(tBu)2Ga}2(μ-OC6H 4O)]n in the solid state
Van Poppel, Laura H.,Bott, Simon G.,Barron, Andrew R.
, p. 11006 - 11017 (2003)
The gallium aryloxide polymer, [{(tBu)2Ga} 2(μ-OC6H4O)]n (1) is synthesized by the addition of Ga(tBu)3 with hydroquinone in a noncoordinating solvent, and reacts with pyridines to yield the yellow compound [(tBu)2Ga(L)]2(μ-OC6H 4O) [L = py (2), 4-Mepy (3), and 3,5-Me2py (4)] via cleavage of the Ga2O2 dimeric core. The analogous formation of Ga(tBu)2(OPh)(py) (5) occurs by dissolution of [(tBu)2Ga(μ-OPh)]2 in pyridine. In solution, 2-4 undergo dissociation of one of the pyridine ligands to yield [(tBu)2Ga(L)(μ-OC6H4O)Ga( tBu)2]2, for which the ΔH and ΔS have been determined. Thermolysis of compounds 2-4 in the solid-state results in the loss of the Lewis base and the formation of 1. The reaction of 1 or [(tBu)2Ga-(μ-OPh)]2 with the vapor of the appropriate ligand results in the solid state formation of 2-4 or 5, respectively. The ΔH? and ΔS? for both ligand dissociation and association for the solid-vapor reactions have been determined. The interconversion of 1 into 2-4, as well as [(tBu) 2Ga(μ-OPh)]2 into 5, and their reverse reactions, have been followed by 13C CPMAS NMR spectroscopy, TG/DTA, SEM, EDX, and powder XRD. Insight into this solid-state polycondensation polymerization reaction may be gained from the single-crystal X-ray crystallographic packing diagrams of 2-5. The crystal packing for compounds 2, 3, and 5 involve a head-to-head arrangement that is maintained through repeated ligand dissociation and association cycles. In contrast, when compound 4 is crystallized from solution a head-to-tail packing arrangement is formed, but during reintroduction of 3,5-Me2py in the solid state-vapor reaction of compound 1, a head-to-head polymorph is postulated to account for the alteration in the ΔH? of subsequent ligand dissociation reactions. Thus, the ΔH? for the condensation polymerization reaction is dependent on the crystal packing; however, the subsequent reversibility of the reaction is dependent on the polymorph.
Bifunctional Mechanism of Pyridine Hydrodenitrogenation
Marzari, J. A.,Rajagopal, S.,Miranda, R.
, p. 255 - 264 (1995)
The role of Mo coordinatively unsaturated sites (CUS) and Broensted acidic sites in the hydrodenitrogenation of pyridine was investigated in an atmospheric-pressure microreactor.The test catalysts consisted of nonsulfided Mo oxide supported on Al2O3, SiO2, and silica-aluminas, containing different concentrations of Mo CUS and Broensted acidic sites.The kinetic study revealed that Mo loading and support composition affect the specific activity of Mo and selectivity of the catalysts.For the range of conditions used in this study (360-420 deg C, 1 atm H2, 0.2 molpercent pyridine concentration, differential conversion), the most abundant reaction intermediate was trans-2-pentene, and the rate-limiting step was the hydrogenation of the ring.Thus, the overall activity was correlated with the concentration of Mo CUS, which are the hydrogenation sites.The yield of denitrogenated product was also correlated with concentration of CUS.The Broensted acidic sites determined the selectivity towards the observed cracking, isomerization, and alkylation products.
A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
García-Domínguez, Andrés,Gonzalez, Jorge A.,Leach, Andrew G.,Lloyd-Jones, Guy C.,Nichol, Gary S.,Taylor, Nicholas P.
supporting information, (2022/01/04)
The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3-nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
Metal-Free Deoxygenation of Amine N-Oxides: Synthetic and Mechanistic Studies
Lecroq, William,Schleinitz, Jules,Billoue, Mallaury,Perfetto, Anna,Gaumont, Annie-Claude,Lalevée, Jacques,Ciofini, Ilaria,Grimaud, Laurence,Lakhdar, Sami
, p. 1237 - 1242 (2021/06/01)
We report herein an unprecedented combination of light and P(III)/P(V) redox cycling for the efficient deoxygenation of aromatic amine N-oxides. Moreover, we discovered that a large variety of aliphatic amine N-oxides can easily be deoxygenated by using only phenylsilane. These practically simple approaches proceed well under metal-free conditions, tolerate many functionalities and are highly chemoselective. Combined experimental and computational studies enabled a deep understanding of factors controlling the reactivity of both aromatic and aliphatic amine N-oxides.
