121-44-8Relevant articles and documents
Probing the compound I-like reactivity of a bare high-valent oxo iron porphyrin complex: The oxidation of tertiary amines
Chiavarino, Barbara,Cipollini, Romano,Crestoni, Maria Elisa,Fornarini, Simonetta,Lanucara, Francesco,Lapi, Andrea
, p. 3208 - 3217 (2008)
The mechanisms of oxidative N-dealkylation of amines by heme enzymes including peroxidases and cytochromes P450 and by functional models for the active Compound I species have long been studied. A debated issue has concerned in particular the character of the primary step initiating the oxidation sequence, either a hydrogen atom transfer (HAT) or an electron transfer (ET) event, facing problems such as the possible contribution of multiple oxidants and complex environmental effects. In the present study, an oxo iron(IV) porphyrin radical cation intermediate 1, [(TPFPP)?+Fe IV=O]+ (TPFPP = meso-tetrakis (pentafluorophenyl) porphinato dianion), functional model of Compound I, has been produced as a bare species. The gas-phase reaction with amines (A) studied by ESI-FT-ICR mass spectrometry has revealed for the first time the elementary steps and the ionic intermediates involved in the oxidative activation. Ionic products are formed involving ET (A?+, the amine radical cation), formal hydride transfer (HT) from the amine ([A(-H)]+, an iminium ion), and oxygen atom transfer (OAT) to the amine (A(O), likely a carbinolamine product), whereas an ionic product involving a net initial HAT event is never observed. The reaction appears to be initiated by an ET event for the majority of the tested amines which included tertiary aliphatic and aromatic amines as well as a cyclic and a secondary amine. For a series of N,N-dimethylanilines the reaction efficiency for the ET activated pathways was found to correlate with the ionization energy of the amine. A stepwise pathway accounts for the C-H bond activation resulting in the formal HT product, namely a primary ET process forming A?+, which is deprotonated at the α-C-H bond forming an N-methyl-N-arylaminomethyl radical, A(-H)?, readily oxidized to the iminium ion, [A(-H)]+. The kinetic isotope effect (KIE) for proton transfer (PT) increases as the acidity of the amine radical cation increases and the PT reaction to the base, the ferryl group of (TPFPP)FeIV=O, approaches thermoneutrality. The ET reaction displayed by 1 with gaseous N,N-dimethylaniline finds a counterpart in the ET reactivity of FeO+, reportedly a potent oxidant in the gas phase, and with the barrierless ET process for a model (P)?+FeIV=O species (where P is the porphine dianion) as found by theoretical calculations. Finally, the remarkable OAT reactivity of 1 with C6F 5N(CH3)2 may hint to a mechanism along a route of diverse spin multiplicity.
Structure and dynamic behavior of phosphine gold(I)-coordinated enamines: Characterization of α-metalated iminium ions
Sriram, Madhavi,Zhu, Yuyang,Camp, Andrew M.,Day, Cynthia S.,Jones, Amanda C.
, p. 4157 - 4164 (2014)
Cationic gold(I) enamine complexes with the (t-Bu)2(o-biphenyl) phosphine ligand were isolated and characterized by NMR spectroscopy and X-ray crystallography. The complexes display highly distorted coordination modes that are consistent with characterization as α-metalated iminium ions. The barrier to rotation around the formal enamine C-C double bond has been measured in a geminally disubstituted enamine complex, and it is comparable to the barrier to C-C single-bond rotation in electronically restricted alkanes. With additional substitution on the enamine double bond, the complexes remain highly distorted, and the reaction of a mixture of E and Z enamines results in formation of a stereochemically pure gold complex. A survey of binding constants reveals enamines to be significantly stronger donors than any alkenes examined to date, and in the case of a geminally disubstituted enamine, the coordination is stronger even than that of triethylamine. The high stability drives the isomerization of an internal enamine complex generated from an intramolecular hydroamination reaction, to the exocyclic double-bond isomer.
Solvent influence on the thermodynamics for hydride transfer from bis(diphosphine) complexes of nickel
Connelly Robinson, Samantha J.,Zall, Christopher M.,Miller, Deanna L.,Linehan, John C.,Appel, Aaron M.
, p. 10017 - 10023 (2016)
The thermodynamic hydricity of a metal hydride can vary considerably between solvents. This parameter can be used to determine the favourability of a hydride-transfer reaction, such as the reaction between a metal hydride and CO2 to produce formate. Because the hydricities of these species do not vary consistently between solvents, reactions that are thermodynamically unfavourable in one solvent can be favourable in others. The hydricity of a water-soluble, bis-phosphine nickel hydride complex was compared to the hydricity of formate in water and in acetonitrile. Formate is a better hydride donor than [HNi(dmpe)2]+ by 7 kcal mol-1 in acetonitrile, and no hydride transfer from [HNi(dmpe)2]+ to CO2 occurs in this solvent. The hydricity of [HNi(dmpe)2]+ is greatly improved in water relative to acetonitrile, in that reduction of CO2 to formate by [HNi(dmpe)2]+ was found to be thermodynamically downhill by 8 kcal mol-1. Catalysis for the hydrogenation of CO2 was pursued, but the regeneration of [HNi(dmpe)2] under catalytic conditions was unfavourable. However, the present results demonstrate that the solvent dependence of thermodynamic parameters such as hydricity and acidity can be exploited in order to produce systems with balanced or favourable overall thermodynamics. This approach should be advantageous for the design of future water-soluble catalysts.
Absolute rate constants for some reactions of the triethylamineboryl radical and the borane radical anion
Sheeller, Brad,Ingold, Keith U.
, p. 480 - 486 (2001)
Laser flash photolysis (LFP) of dj-tert-butyl peroxide or dicumyl peroxide at ambient temperatures in the presence of Et3N→BH3 or BH4- generated the title radicals which were found to have broad, featureless absorptions in the visible region. Rate constants for H-atom abstraction from Et3N→BH3 by cumyloxyl radicals show a small solvent dependence, e.g. 12 × 107 and 2.2 × 107 dm3 mol-1 s-1 in isooctane and acetonitrile, respectively. Rate constants for halogen atom abstraction by Et3N→BH2. and BH3.- from a number of chlorides and bromides were determined by LFP and by competitive kinetics, e.g., for Et3N→BH2. + CCl4/PhCH2Cl/CH3(CH2)2Cl, k = 4.4 × 109/1.1 × 107/5.1 × 105 dm3 mol-1 s-1 and for BH3.- + CCl4/PhCH2Cl, k = 2.0 × 109/3.0 × 107 dm3 mol-1 s-1. Rates of addition of Et3N→BH2. to 1-and 1,1-substituted olefins increase dramatically as the electron affinity of the olefin increases, confirming the nucleophilic character of amine-boryl radicals. A comparison of the present results with literature data for the addition of olefins of four nucleophilic carbon-centered radicals proves that Et3N→BH2. is by far the most nucleophilic radical for which kinetic data are available. A few rate constants for abstraction of hydrogen from electron-deficient carbon by Et3N→BH2. are also reported.
Reactions of diethylamine and ethylene catalyzed by PtII or Pt0 - Transalkylation vs. hydroamination
Dub, Pavel A.,Bethegnies, Aurelien,Poli, Rinaldo
, p. 5167 - 5172 (2011)
PtBr2/nBu4PBr (without solvent) or K 2PtCl4/NaBr (in water) have been shown to efficiently catalyze the hydroamination of ethylene by aniline and are poor catalysts for the hydroamination of ethylene by diethylamine. A DFT study on the hydroamination mechanism indicates that the energetic span of the C 2H4/Et2NH catalytic cycle is close to that of the C2H4/PhNH2 cycle. The poor performance is attributed to rapid catalyst degradation with reduction to metallic platinum. Pt0, on the other hand, catalyzes a transalkylation process, partially transforming Et2NH into Et3N, EtNH2 and NH3. This process is inhibited by C2H4. Mechanistic considerations for the Pt0-catalyzed transalkylation process are presented. Copyright
Validated HPLC and stability-indicating densitometric chromatographic methods for simultaneous determination of camylofin dihydrochloride and paracetamol in their binary mixture
Abdel Razeq, Sawsan A.,Khalil, Israa A.,Mohammd, Samah A.
, p. 2587 - 2597 (2020)
Two accurate, sensitive, precise and selective HPLC and stability-indicating TLC methods were developed for the simultaneous determination of camylofin-2HCl and paracetamol. Forced acid, alkali and oxidative degradation of camylofin-2HCl?were tried where complete degradation was achieved using 5?N HCl. HPLC method was developed to determine the mixture of the two drugs using Zorbax NH2 column and a mobile phase of 0.5percent triethylamine and pH 3.0 adjusted with 0.1percent phosphoric acid and methanol (70:30 v/v) over concentration ranges of 3–90 and 10–95?μg/mL for camylofin-2HCl and paracetamol, respectively.TLC method was used for the separation of camylofin from its acid degradate and paracetamol using chloroform–methanol–acetone–conc. ammonia (8:2:2:0.1, by volume) as developing system and band scanning at 254 nm over concentration ranges of 5–40?μg/band for camylofin-2HCl and 0.1–0.5?μg/band for paracetamol. The validation of two methods was carried out according to ICH guideline. Accuracy ranged between 98.47 and 100.67percent for the two methods with acceptable precision RSDpercent ranging between 0.66 and 1.47percent.
Production of hcooh/net3 adducts by co2/h2 incorporation into neat NEt3
Preti, Debora,Squarcialupi, Sergio,Fachinetti, Giuseppe
, p. 2581 - 2584 (2010)
Chemical Equaction Presented Adding HCOOH to NEt3 gives a biphasic system of amine and an adduct with a molar acid/amine ratio (AAR) of 1.33. In the presence of a suitable catalyst, CO2/H 2 (1:1) acts as HCOOH if both amine and 1.33-adduct phases are present. For example, at 4O°C and 120 bar, neat amine, doped with both 1.33 adduct and catalyst, is quantitatively converted into 1.78 adduct, which is distilled as an azeotrope with AAR = 2.35.
Soluble polymer-supported synthesis of tertiary amines
Chen, Zuxing,Yang, Guichun,Zhang, Zhaojun
, p. 729 - 734 (2003)
The synthesis of tertiary amines on a modified soluble polymer, poly(ethylene glycol) (PEG), is described. The PEG-bound quaternary intermediates were assembled via Michael addition reaction, followed by alkylation. Cleavage from the soluble polymer support was induced by insoluble weak basic resin, to afford the target tertiary amines in excellent purity.
Effects of metal particle size in gas-phase hydrogenation of acetonitrile over silica-supported platinum catalysts
Arai, Masahiko,Takada, Yoshiomi,Nishiyama, Yoshiyuki
, p. 1968 - 1973 (1998)
The gas-phase hydrogenation of acetonitrile was studied with silica-supported platinum catalysts of which the degrees of metal dispersion were widely changed by reduction conditions. The activities were found to decrease gradually during the course of reaction for all the catalysts examined. The initial rate of reaction increased with an increase in the degree of platinum dispersion, D. Triethylamine was the only main product irrespective of D and period of reaction time. The initial turnover frequency, TOF0, was shown to be smaller for larger D values. This dependence of TOF0 on D was explained by the electronic state of the surface of the platinum particles and the state of acetonitrile molecules adsorbed on them on the basis of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy measurements. The surface layer of smaller particles is more favorable for the adsorption of acetonitrile. The acetonitrile is adsorbed by platinum with the electron lone pair of nitrogen in the antibonding orbital, but electron back-donation does not takes place. As a result, the C≡N bonds of acetonitrile adsorbed on smaller particles are stronger and more difficult to hydrogenate.
CIDEP Study of Durosemiquinone Radical in Various Solvents
Kanemoto, Akihiko,Niizuma, Sigeya,Konishi, Siro,Kokubun, Hiroshi
, p. 46 - 50 (1983)
F-pair polarization and triplet mechanism (TM) polarization of durosemiquinone radical produced by light irradiation of duroquinone-phenol systems were discriminated at 260 K in a simple way based on the analysis of the enhancement factors in the steady-state method with intermittent light irradiation.Both polarizations are not so sensitive to viscosity or polarity of solvents.TM enhancement factor is nearly constant (-0.8) in wide range of viscosity (2.5-25 cP, 1 cP=0.001 Pa s).F-pair polarization is suppressed in some extent by halogenated solvents while TM polarization is not affected by such solvents.
