On the mechanism of the Fe(CO)5-catalyzed Kharasch reaction

Regioselectivity and diastereoselectivity of the addition of BrCCl₃ to (R)-3-(E)-cinnamoyl-4-phenyloxazolidin-2-one (1) and (R)-3-(E)-acryloyl-4-phenyloxazolidin-2-one (2) catalyzed by Fe(CO)₅ or initiated with benzoyl peroxide were investigated. Stereochemistry of the reaction of BrCCl₃ with the a-complexes (4R,S,S)-²-(3-(E)-cinnamoyl-4-phenyl-oxazolidin-2-one)irontetracarbonyl (3a) and (4R,R)-²-(3-acryloyl-4-phenyloxazolidin-2-one)irontetracarbonyl (4b) was also studied. The results obtained allow the following conclusions to be drawn: (1) the thermal Kharasch reaction catalyzed by Fe(CO)₅ proceeds by a redox catalysis mechanism; (2) iron (in any of its oxidation states) is not coordinated to olefins in the transition state of the reaction; (3) the transfer of the halogen atom on the radical adduct probably occurs inside a radical-iron cation pair.Yu. T. Struchkov is deceasedTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 640–648, March, 1996.     

Addition of halogenoacetic esters to aldehydes and ketones in the presence of Fe(CO)5

The use of complex-forming solvents and variations in the reaction temperature made it possible to prepare α-halogeno β-hydroxy carboxylic esters upon addition of halogenoacetic esters to aldehydes and ketones promoted by iron pentacarbonyl. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 718–720, April, 2000.     

Regioselective hydrothiolation of terminal acetylene catalyzed by magnetite (Fe3O4) nanoparticles

Herein, we report a new and solvent-free methodology for the preparation of vinyl thioethers from terminal alkynes and thiols, using magnetite (Fe₃O₄) nanoparticles as a recyclable catalyst. With this greener method, the desired vinyl thioethers were achieved in good yields and with good stereoselectivity. In addition, the catalyst was easily recovered using a simple external magnet and reused for further catalytic reactions without significant loss of activity up to the fifth cycle.     

C6F5X＋（X=Cl,Br,I,CH3）离子的理论研究

用DFT B3LYP方法及6-311G（d,p）,6-311＋G（d,p）和LanL2dz基组,对C6F5X＋（X=Cl,Br,I,CH3）阳离子做了理论研究,优化了它们的电子基态的构型,计算了对应分子的垂直电离势（VIP）和绝热电离势（AIP）.结果表明四种离子的构型的对称点群和对应分子相同,但构型参数有明显差别.B...     

Effect of alkali additives on the kinetics of WO3+CCl4 reaction

The chlorination kinetics of alkali-added (K and Li) tungsten trioxide were studied by thermogravimetry, using gaseous CCl₄ as chlorinating agent. The reactivity of the modified samples was compared to the results on the chlorination of pure WO₃. Similar apparent activation energies were found for the pure and alkali-added samples. However, potassium additive resulted in a strong decrease of the initial reaction rate, while surface lithium has no influence on it.During the chlorination a continuous decrease of the linear reaction rate was observed for both samples, which was explained by retarding effects of surface by-products and alkali additives. For describing the isothermal TG curves an appropriate kinetic model, based on the monotonously increasing inhibition of these species was assumed. The curve calculated with this model fits well to the experimental results.

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Zusammenfassung Mittels Thermogravimetrie wurde die Chlorierungskinetik von alkaliversetztem (K und Li) Wolframtrioxid untersucht, wobei CCl₄ als Chlorierungsreagens fungierte. Die Reaktivität der modifizierten Proben wurden mit der von reinem WO₃ verglichen. Für die reinen und für die alkaliversetzten Proben wurden ähnliche scheinbare Aktivierungsenergien gefunden. Der Zusatz von Kalium verursacht jedoch eine starke Abnahme der ursprünglichen Reaktionsgeschwindigkeit, während oberflächiges Lithium keinen Effekt zeigt.Während der Chlorierung wurde eine ständige Senkung der linearen Reaktionsgeschwindigkeit für beide Proben festgestellt, was mit Rückhalteeffekten von oberflächigen Nebenprodukten und Alkalizusätzen erklärt wird. Zur Beschreibung der isothermen TG-Kurven wurde ein entsprechendes kinetisches Modell angenommen, welches auf einer monoton steigenden Inhibition dieser Proben basiert. Die auf der Grundlage dieses Modelles berechnete Kurve stimmt recht gut mit den experimentellen Ergebnissen überein.

     

Decolorization of C.I. Reactive Red 2 by ozonation catalyzed by Fe(II) and UV

This work evaluated the effects of pH on decolorization of C.I. Reactive Red 2 by O₃, O₃/Fe(II), UV/O₃ and UV/O₃/Fe(II) systems. At pH 4, the decolorization rate constants of O₃, O₃/Fe(II), UV/O₃ and UV/O₃/Fe(II) systems were 1.78, 3.11, 2.04 and 3.18 hr⁻¹, respectively. The decolorization rates and effective energy consumption constants of all systems were higher under basic conditions than under acidic conditions.     

The reaction of SF5Br with select 1,2-dihaloethylenes

SF₅Br reacts with 1,2-haloethylenes (F, Cl, Br) in distinct ways. In the case of F- and Cl-olefins, the expected addition occurs while with 1,2-dibromoethylene a metathetical reaction yielding in a clean reaction a 1:1 mixture of SF₅CHCHBr and CHBr₂CHBr₂ is found. The mechanism for this reaction is discussed.     

Theoretical study on the reaction mechanism of (CH3)3CO+CO

The reaction mechanism of (CH₃)₃CO with CO has been theoretically investigated using density-functional theory (DFT) calculations at B3LYP/6-31G* level. In order to get more reliable energy values the single-point energy is evaluated at CCSD (T)/6-31++G** level. The results show that the reaction is multi-channel and the reaction of (CH₃)₃CO radical with CO mostly produces (CH₃)₃C + CO₂. The reaction could play a role in eliminating air pollution.     

Building und Reaktionen des Phosphanyliden-Phosphorans (tBu)2P?P = PX(tBu)2 (X = Br,Cl)

Formation and Reaction of the Phosphanylidene-phosphorane (tBu)₂P? P = PX(tBu)₂ (X = Br, Cl) The formation of (tBu)₂P? P = P(Br)tBu₂ 1 from [(tBu)₂P]₂PLi and BrH₂C? CH₂Br begins with an exchange of Li against Br and is then determined by the migration of Br from the secondary P atom in [(tBu)₂P]₂PBr 6 to the primary P in 1 . Similarly, (tBu)₂P? P = PC1(tBu)₂ 2 is obtained starting from PCl₃ and LiP(tBu)₂. The formation of Phospanylidene—phosporane is not influenced by the choice o the halogene substituent, but the presence of the tBu groups is strongly required. (tBu)₂P? P(Li)? P(SiMe₃)₂ e. g., yields (tBu)₂P? P(br)? P(SiMe₃)₂ with BrH₂C? CH₂Br; however neither this nor (tBu)₂P? P(Cl)? P(SiMe₃)₂ do rearrange to a Phosphanylidene-phosphorane. The F₃C substituent could be neglected in this investigation as [(F₃C)₂P]₂P? SiMe₃ cannot be lithiated by means of BuLi. Compounds 1 and 2 display a charateristic temperature dependent behavior. While 1 at +20°C decomposes via the reactive intermediate (tBu)₂P? P to from the cyclophosphanes P₃[P(tBu)₂]₄, it gives crystals of [(tBu)₂P]₂P? p[P(tBu)₂]₂ at ?20°C (from a solution in toluene). Reacting 1 with tBuLi produces (tBu)₂P? P = P(H)tBu₂ 20 and (tBu)₂P? P(H)? P(tBu)₂ 14 . Initially, a transmetallation yield tBuBr and (tBu)₂ P? P=Pli(tBu)₂ 21 ,then LiBr and isobutene are eliminated and 20 is formed which can rearrange to produce 14 . Without the elimination of isobutene, 1 react with nBuLi to give 21 witch can be trapped with Me₃SiCl as (tBu)₂P? P(tBu)₂ 23 . The main product in in this reaction is however [(tBu)₂P]₂P? nBu 22 .     

Chemistry of ruthenium in N2P2X2 (X = Cl, Br) coordination sphere: Synthesis, characterization and reactivities

Reaction of 2-(phenylazo)pyridine (pap) with [Ru(PPh₃)₃X₂] (X = Cl, Br) in dichloromethane solution affords [Ru(PPh₃)₂(pap)X₂]. These diamagnetic complexes exhibit a weakdd transition and two intense MLCT transitions in the visible region. In dichloromethane solution they display a one-electron reduction of pap near − 0.90 V vs SCE and a reversible ruthenium(II)-ruthenium(III) oxidation near 0.70 V vs SCE. The [Ru^III(PPh₃)₂(pap)Cl₂]⁺ complex cation, generated by coulometric oxidation of [Ru(PPh₃)₂(pap)Cl₂], shows two intense LMCT transitions in the visible region. It oxidizes N,N-dimethylaniline and [Ru^II(bpy)₂Cl₂] (bpy = 2,2′-bipyridine) to produce N,N,N′,N′-tetramethylbenzidine and [Ru^III(bpy)₂Cl₂]⁺ respectively. Reaction of [Ru(PPh₃)₂(pap)X₂] with Ag⁺ in ethanol produces [Ru(PPh₃)₂(pap)(EtOH)₂]²⁺ which upon further reaction with L (L = pap, bpy, acetylacetonate ion(acac⁻) and oxalate ion (ox²⁻)) gives complexes of type [Ru(PPh₃)₂(pap)(L)]ⁿ⁺ (n = 0, 1, 2). All these diamagnetic complexes show a weakdd transition and several intense MLCT transitions in the visible region. The ruthenium(II)-ruthenium(III) oxidation potential decreases in the order (of L): pap > bpy > acac⁻ > ox²⁻. Reductions of the coordinated pap and bpy are also observed.     

Facile Synthesis of Bis(indolyl)methanes catalyzed by Ferric Dodecyl Sulfonate [Fe(DS)3] in Water at Room Temperature

Ferric dodecyl sulfonate [Fe(DS)₃] is easily prepared and can be used as a Lewis acid surfactant catalyst in water to conduct the highly efficient electrophilic substitution reaction of indoles with aliphatic or aromatic aldehydes at room temperature.     

Synthesis,crystal structure,magnetism, and absorption spectra of A2UX5 Type Halides (A = K,Rb; X = Cl,Br, I)

The ternary uranium(III) halides A₂UX₅ (A = K, Rb; X = Cl, Br, I) have been prepared from the binary components AX and UX₃ in sealed tantalum containers. According to their Guinier X-ray powder patterns, they all crystallize with the K₂PrCl₅/Y₂HfS₅ type of structure. Lattice constants for ambient temperature are reported. Single-crystal structure refinemens were undertaken for K₂UI₅ and Rb₂UCl₅. Magnetic susceptibility data were recorded with a SQUID magnetometer from liquid helium to room temperature. One-dimensional (intrachain) and three-dimensional antiferromagnetic ordering occur at low temperatures dependent upon the U³⁺? U³⁺ distance. Absorption spectra were recorded between 4 000 and 28 000 cm^?1. They show f—f transitions typical for U³⁺ and, depending on the halide, very strong f—d transitions above 14 000 to 15 000 cm^?1, respectively.     

A convenient and efficient method for incorporation of pentafluorosulfanyl (SF5) substituents into aliphatic compounds

Both SF₅Cl and SF₅Br undergo smooth, high yield addition to alkenes and alkynes under the mild free radical chain reaction conditions of triethylborane initiation at low temperature, although the SF₅Br chemistry is somewhat limited by its competing high electrophilic reactivity with electron rich alkenes. The SF₅Cl addition reaction is relatively insensitive to a wide variety of non-allylic functionalities.     

Effect of Ligand Field Strength on the Spin Crossover Behaviour in 5‐X‐SalEen (X=Me,Br and OMe) Based Fe(III) Complexes

The reaction of Fe(NCS)₃ prepared in situ in MeOH with 5‐X‐SalEen ligands (5‐X‐SalEen=condensation product of 5‐substituted salicylaldehyde and N‐ethylethylenediamine) provided three Fe(III) complexes, [Fe(5‐X‐SalEen)₂]NCS; X=Me ( 1 ), X=Br ( 2 ), X=OMe ( 3 ). All the complexes reveal similar structural features but a very different magnetic profile. Complex 1 shows a gradual spin crossover while complexes 2 and 3 show a sharp spin transition. The T_1/2 for complex 2 is 237 K while for complex 3 it is much higher with a value of 361 K. The spin transition temperature is shifted towards higher temperature with increasing electron‐donation ability of the ligand substituents. This experimental observation has been rationalized with DFT calculations. UV‐Vis and cyclic voltammetry studies support the fact that the electron density on the ligand increases from Me to Br to OMe substituents. To understand the change in spin states, temperature‐dependent EPR spectra have been recorded. The spin state equilibrium in the liquid state has been probed with Evans NMR spectroscopic method, and thermodynamic parameters have been evaluated for all complexes.     

A comparison of quantitative theoretical results of the bonding in Ni(CO)4 and Ni(N2)4

Using non-empirical calculations the details of bonding in Ni(CO)₄ and in the analogous Ni(N₂)₄ are investigated.For Ni(CO)₄ some previous results are confirmed. In the calculation on Ni(N₂)₄ the close resemblance with Ni(CO)₄ is quite remarkable. The main difference is contained in the fact that carbon has a lower -electron density than nitrogen and that therefore the *-orbital in CO is lower in energy and geometrically more favourable for back donation.From the calculations we find a difference in metal-ligand bond energy between the carbonyl complex and the dinitrogen complex of approximately 18 kcal/mol.     

An alternative quinoline synthesis by via Friedländer reaction catalyzed by Yb(OTf)3

Quinolines have been synthesized in very good yields from 2-aminoarylketones and differently substituted carbonyl compounds in the presence of Yb(OTf)₃ as the catalyst. The method is applicable to both cyclic and acyclic carbonyl compounds with only slight differences in the experimental procedure.     

Fe(III)与2,3-二羟基苯磺酸钠配位反应的动力学研究

[H+]在0.01～0.70mol?L-1范围内,离子强度为1.00mol?L-1,[Fe(III)]>>[配体]、[H+]>>[配体]的条件下,研究了Fe(III)与2,3-二羟基苯磺酸钠(Tiron)的配位反应.发现当[H+]≤3.00×10-2mol?L-1时,[Fe(III)]2对反应速率有明显的贡献.求得了相关反应的动力学参数,从而揭示了FeOH2+和FeOH24+与Tiron配位的解离反应途径及FeOH32+的缔合反应机制,并提出了该配位反应的可能机理.     

Investigation on The Thermal Properties of Fe2O(SO4)2. Part II

Fe₂O(SO₄)₂ is a secondary product of the decomposition of FeSO₄⋅H₂O. Part I of this study presents results on the synthesis of Fe₂O(SO₄)₂ in gaseous environment containing either low or high concentration of oxygen. In this paper the existence of differences between the structures of Fe₂O(SO₄)₂ and Fe₂(SO₄)₃ is proved on the basis of a detailed thermal study of Fe₂O(SO₄)₂ upon dynamic heating (differential thermal analysis) and upon isothermal heating (thermal-analytic balance) in various gaseous environments as well as by presenting kinetic data on the processes of decomposition of both compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

Direct Mannich reaction mediated by Fe(Cp)2PF6 under solvent-free conditions

Fe(Cp)₂PF₆ (5 mol %) efficiently catalyzed Mannich reaction of aldehydes, anilines, and ketones under solvent-free condition to give β-amino-ketones in high yield (up to 94%) within 30 min with anti-isomer in excess. Simple experimental conditions and product isolation procedure makes this protocol potential for the development of clean and environment-friendly strategy for the synthesis of β-amino-ketones.     

Intramolecular cyclization of chloral allyl hemiacetal under the action of the Fe(CO)5-DMF system

Chloral allyl hemiacetal undergoes cyclization in the presence of the Fe(CO)₅-DMF system to form 3,3,5-trichloro-2-hydroxytetrahydropyran rather than a butyrolactone derivative. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 750–752, April, 1999.