108-89-4Relevant articles and documents
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.
Synthesis, spectral, thermal and kinetic studies on the adducts with pyridines of tungsten(V) binuclear thiocomplexes with di-isopropyl-dithiocarbamate
Lozano,de Jesús,Lozano
, p. 3127 - 3132 (2006)
We report the synthesis and the thermal and kinetic behaviour of di-μ-sulfido-bis-(sulfido N,N,di-i-propyldithiocarbamate)di-tungsten(V) adducts with pyridine or substituted pyridines, the formula of which is [W2S4(di-i-propyldtc)2B2], where dtc = dithiocarbamate and B = pyridine (Py), 3-methylpyridine (3-MP), 4-methylpyridine (4-MP), 3,5-dimethylpyridine (3,5-DMP), 3-aminopyridine (3-AP) and 4-aminopyridine (4-AP). The synthesized complexes have been identified by IR and electronic spectra, magnetic susceptibility measurements and analytical data. We have also inferred the thermal behaviour and kinetic parameters by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of the thermal decomposition of these adducts in the solid state. From the DSC curves, the activation energies and pre-exponential Arrhenius factors for the endothermic process corresponding to the loss of two moles of coordinated base were calculated. We have also deduced the reaction mechanism using a new non-isothermal kinetic method. Steric hindrance and inductive effects prompted by amino and methyl pyridine functional groups in the adducts formation are discussed. A relationship between the pyridines basicity, infrared and electronic spectral data and activation energies has also been explored.
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.
Pd0-mediated rapid coupling between methyl iodide and heteroarylstannanes: an efficient and general method for the incorporation of a positron-emitting11C radionuclide into heteroaromatic frameworks
Suzuki, Masaaki,Sumi, Kengo,Koyama, Hiroko,Siqin,Hosoya, Takamitsu,Takashima-Hirano, Misato,Doi, Hisashi
, p. 12489 - 12495 (2009)
The Pd0-mediated rapid trapping of methyl iodide with an excess amount of a heteroaryl-substituted tributylstannane has been investigated with the aim of incorporating a shortlived 11C-labelled methyl group into the heteroaromatic carbon frameworks of important organic compounds, such as drugs with various heteroaromatic structures, in order to execute a positron emission tomography (PET) study of vital systems. The reaction was first performed by using our previously developed CH3I/stannane/[Pd 2(dba)3]/ P(o-CH3C6H 4)3/CuCl/K2CO3 (1:40:0.5:2:2:2) system in DMF at 60°C for 5 min (conditions A), however, the reaction gave low yields for various heteroaromatic compounds. Increasing the amount of phosphine ligand (condi tions B) led to a significant improvement in the yield, but the conditions were still not suitable for a range of basic heteroaromatic structures. Use of the CuBr/CsF system (conditions C) also provided a result similar to that obtained under conditions B with an increased amount of the phosphine. Thus, pyridine and related heteroaromatic compounds remained less reactive substrates. The problem was overcome by replacing the DMF solvent with N-methyl-2-pyrolidinone (NMP). The reaction in NMP at 60-100°C for 5 min using a CH3I/stannane/[Pd2-(dba)3]/P(o-CH 3C6H4)3/CuBr/CsF (1:40:0.5:16:2:5) combination (conditions D) gave the methylated products in yields of more than 80% (based on the reaction of CH3I) for all of the heteroaromatic compounds listed in this study. Thus, the combined use of NMP and an increased amount of phosphine is important for promoting the reaction efficiently. The use of this general approach to rapid methylation has been well demonstrated by the synthesis of the PET tracers 2- and 3-[11C]methylpyridines by using [Pd2(dba)3]/P(o-CH3C6H 4)3/CuBr/CsF (1:16:2:5) in NMP at 60°C for 5 min, which gives the desired products in HPLC analytical yields of 88 and 91%, respectively.
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).
Unsaturated aldehydes: a novel route for the synthesis of pyridine and 3-picoline
Luo, Cai-Wu,Chao, Zi-Sheng
, p. 54090 - 54101 (2015)
A novel reaction pathway was developed for the synthesis of pyridine and 3-picoline from the condensation of gas-phase acrolein dimethyl acetal or acrolein diethyl acetal and ammonia over various catalysts in a fixed-bed reactor. ZnO loaded on alkaline-acid sequentially-treated HZSM-5, namely ZnO/HZSM-5-At-acid, was prepared and employed in these reactions for the first time. 3-Picoline, without the generation of 4-picoline, was obtained from the condensation of acrolein dimethyl acetal and ammonia. The ZnO/HZSM-5-At-acid catalyst was proven to be the most promising catalyst relative to other catalysts in this study. The stability of the ZnO/HZSM-5-At-acid catalyst was remarkably higher than that of the ZnO/HZSM-5 catalyst. The catalysts were characterized using XRD, 27Al MAS NMR, XPS, UV-vis DRS, N2-physisorption, NH3-TPD and TG technologies and the results revealed that the pore structure, acidity and location of ZnO had great influence on the total yield of pyridine and 3-picoline, and the catalyst stability.
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.
Thermal study of [Pd(2-Phpy)Cl(L)] complexes (L=pyridines and amines)
Perez,Sanchez,Garcia,Serrano,Lopez
, p. 361 - 370 (2001)
The complex [Pd(2-Phpy)(μ-Cl)]2 reacts with pyridines (L=pyridine, α-picoline and γ-picoline), amines (L=isopropylamine, tert-butylamine) and ammonia to form the corresponding ortho-palladated derivatives [Pd(2-Phpy)CIL]. The compounds have bee
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].
