100-67-4Relevant articles and documents
New Cu-based catalysts supported on TiO2 films for Ullmann SNAr-type C-O coupling reactions
Benaskar, Faysal,Engels, Volker,Rebrov, Evgeny V.,Patil, Narendra G.,Meuldijk, Jan,Thuene, Peter C.,Magusin, Pieter C. M. M.,Mezari, Brahim,Hessel, Volker,Hulshof, Lumbertus A.,Hensen, Emiel J. M.,Wheatley, Andrew E. H.,Schouten, Jaap C.
, p. 1800 - 1810 (2012)
New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt %. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, 63Cu nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO2 catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64 % on the Cu/nonporous TiO2 at 120 °C. The highest product yield of 84 % was obtained on the Cu/mesoporous TiO2 at 140 °C, corresponding to an initial reaction rate of 104 mmol gcat-1 s-1. The activation energy on the Cu/mesoporous TiO2 catalyst was found to be (144±5) kJ mol-1, which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123±3 kJ mol-1) and almost twice the value observed over the catalysts deposited onto the non-porous TiO2 support (75±2 kJ mol-1). Copyright
Mechanism of the Base-Catalyzed Elimination of Para-Substituted Phenoxides from 4-(Aryloxy)azetidin-2-ones
Fedor, Leo R.
, p. 5094 - 5097 (1984)
4-(Aryloxy)azetidin-2-ones 4-7 react in dilute aqueous alkali to give 3-hydroxyacrylamide oxyanion and para-substituted phenolate ions.Similarly, 4-(aryloxy)-3,3-dimethylazetidin-2-ones 8-11 give 2,2-dimethylcarboxaldoacetamide and para-substituted phenolate ions.Reactivity is proportional to the fraction of (aryloxy)azetidin-2-one anions, Ka/(Ka + ).Kinetic pKa's of 4-11 and first-order k2's for (suggested) reversible E1cB elimination of para-substituted phenoxide ions from N-1 anions are reported.Reactions are further characterized kinetically by solvent deuterium isotope effects: kOH/kOD = ca. 0.5, ρ(k2) = 2.2 for 4-7 and ρ(k2) = 2.7 for 8-11, and βlg = -0.65 for 4-7 and βlg = -0.75 for 8-11.
Enthalpy-entropy correlations in reactions of aryl benzoates with potassium aryloxides in dimethylformamide
Khalfina, Irina A.,Vlasov, Vladislav M.
, p. 266 - 282 (2013)
Temperature dependences of the relative reactivity of potassium aryloxides XC6H4O-K+ toward 4-nitrophenyl (1), 3-nitrophenyl (2), 4-chlorophenyl (3), and phenyl (4) benzoates in dimethylformamide (DMF) were studied using the competitive reactions technique. The rate constants kX for the reactions of 1 with potassium 4-cyanophenoxide, 2 with potassium 3-bromophenoxide, 3 with potassium 3-bromo-, 4-bromo-, and unsubstituted phenoxides, 4 with potassium 4-methoxy- and 3-methylphenoxides were measured at 25°C. Correlation analysis of the relative rate constants kX/kH(3-Me) and differences in the activation parameters (δδH≠and δ δS ≠) of competitive reactions revealed the existence of six isokinetic series. We investigated the substituent effect of X on the activation parameters for each isokinetic series and concluded that the reactions of aryl benzoates PhCO2C6H4Y with potassium aryloxides in DMF proceed via a four-step mechanism. The large ρ0(Y) and ρXY values at 25°C obtained for the reactions of 1-3 with potassium aryloxides with an electron-donating substituent refer to the rate-determining formation of the spiro-σ-complex. The Hammett plots for the reactions of 1 and 2 exhibit a downward curvature, causing the motion of the transition state for the rate-determining step according to a Hammond effect as the substituent in aryloxide changes from electron-donating to electron-withdrawing. Analysis of data in the terms of two-dimensional reaction coordinate diagrams leads to the conclusion that significant anti-Hammond effects arise in the cases of ortho-substituted and unsubstituted substrates. It was shown that the isokinetic and compensation effects observed for the reactions of aryl benzoates with potassium aryloxides in DMF can be interpreted in the terms of the electrostatic bonding between the reaction centers.
Combined dual substituent constant and activation parameter analysis assigns a concerted mechanism to alkaline ethanolysis at phosphorus of Y-substituted phenyl diphenylphosphinates
Um, Ik-Hwan,Park, Jee Eun,Shin, Young-Hee
, p. 3539 - 3543 (2007)
Second-order rate constants have been measured for reactions of Y-substituted phenyl diphenylphosphinates (1a-h) with EtO-K + in anhydrous ethanol. A linear Bronsted-type plot is obtained with βLg = -0.54, a typical βLg value for reactions which proceed through a concerted mechanism. The Hammett plots correlated with σo and σ- constants are linear but exhibit many scattered points, while the corresponding Yukawa-Tsuno plot results in excellent linear correlation with r = 0.41. The r value of 0.41 indicates that the leaving group departs at the rate-determining step (RDS) whether the reactions proceed through either a concerted or a stepwise mechanism. However, a stepwise mechanism in which departure of the leaving group occurs at the RDS is excluded since the incoming EtO- ion is much more basic and a poorer leaving group than the leaving aryloxide. The ΔH? values determined in the current reactions are strongly dependent on the nature of the substituent Y, while the ΔS ? values remain constant on changing the substituent Y in the leaving group, i.e., from Y = H to Y = 4-NO2 and Y = 3,4-(NO 2)2. These ΔH? and ΔS ? trends also support a concerted mechanism. The Royal Society of Chemistry.
The unusual outcome of the reaction of potassium anions with phenyl glycidyl ether
Stolarzewicz, Andrzej,Grobelny, Zbigniew,Kowalczuk, Marek
, p. 111 - 114 (1995)
The formation of potassium phenolate, potassium hydroxide, propylene and ethylene in the reaction of phenyl glycidyl ether with the potassium anions has been demonstrated.Evidently, the PhO-CH2 bond is remarkably readily cleaved by the K- ion under these conditions.Keywords: Potassium anions; Crown ethers; Oxiranes
Ambident Reactivity of Phenolate Anions Revisited: A Quantitative Approach to Phenolate Reactivities
Mayer, Robert J.,Breugst, Martin,Hampel, Nathalie,Ofial, Armin R.,Mayr, Herbert
, p. 8837 - 8858 (2019/07/08)
Prompted by the observation that the regioselectivities of phenolate reactions (C versus O attack) are opposite to the predictions by the principle of hard and soft acids and bases, we performed a comprehensive experimental and computational investigation of phenolate reactivities. Rate and equilibrium constants for the reactions of various phenolate ions with benzhydrylium ions (Aryl2CH+) and structurally related quinone methides have been determined photometrically in polar aprotic solvents. Quantum chemical calculations at the SMD(MeCN)/M06-2X/6-31+G(d,p) level confirmed that O attack is generally favored under kinetically controlled conditions, whereas C attack is favored under thermodynamically controlled conditions. Exceptions are diffusion-limited reactions with strong electrophiles, which give mixtures of products arising from O and C attack, as well as reactions with metal alkoxides in nonpolar solvents, where oxygen attack is blocked by strong ion pairing. The Lewis basicity (LB) and nucleophilicity (N, sN) parameters of phenolates determined in this work can be used to predict whether their reactions with electrophiles are kinetically or thermodynamically controlled and whether the rates are activation- or diffusion-limited. Comparison of the measured rate constants for the reactions of phenolates with carbocations with the Gibbs energies for single-electron transfer manifests that these reactions proceed via polar mechanisms.
Impact of aryloxy initiators on the living and immortal polymerization of lactide
Chile,Ebrahimi,Wong,Aluthge,Hatzikiriakos,Mehrkhodavandi
, p. 6723 - 6733 (2017/07/10)
This report describes two different methodologies for the synthesis of aryl end-functionalized poly(lactide)s (PLAs) catalyzed by indium complexes. In the first method, a series of para-functionalized phenoxy-bridged dinuclear indium complexes [(NNO)InCl]2(μ-Cl)(μ-OPhR) (R = OMe (1), Me (2), H (3), Br (4), NO2 (5)) were synthesized and fully characterized. The solution and solid state structures of these complexes reflect the electronic differences between these initiators. The polymerization rates correlate with the electron donating ability of the phenoxy initiators: the para-nitro substituted complex 5 is essentially inactive. However, the para-methoxy variant, while less active than the ethoxy-bridged complex [(NNO)InCl]2(μ-Cl)(μ-OEt) (A), shows sufficient activity. Alternatively, aryl-capped PLAs were synthesized via immortal polymerization of PLA with A in the presence of a range of arylated chain transfer agents. Certain aromatic diols shut down polymerization by chelating one indium centre to form a stable metal complex. Immortal ROP was successful when using phenol, and 1,5-naphthalenediol. These polymers were analysed and chain end fidelity was confirmed using 1H NMR spectroscopy, MALDI-TOF mass spectrometry, and UV-Vis spectroscopy. This study shed light on possible speciation when attempting to generate PLA-lignin copolymers.
Mechanism and stereochemistry of domino reaction of 2,3-dichloroprop-1-ene with diphenyl dichalcogenides in the system hydrazine hydrate - KOH
Levanova,Vakhrina,Grabel'Nykh,Rozentsveig,Russavskaya,Albanov,Korchevin
, p. 1722 - 1727 (2015/05/20)
A new scheme of the domino reactions of diphenyl dichalcogenides with 2,3-dichloroprop-1-ene in the system hydrazine hydrate - KOH was suggested, which included nucleophilic substitution of the allylic chlorine atom in dichloropropene, dehydrochlorination of the product obtained with the formation of an allene derivative, addition of a nucleophile to the allene system, allene-acetylene rearrangement, addition of a nucleophile to the triple bond with the formation of a Z-adduct, isomerization of a 2,3-dichalcogenide product to Z-1,2-dichalcogenylprop-1-enes, and isomerization of Z-adducts to E-isomers. The most plausible mechanisms of individual steps, involving carbanions stabilized by the α-chalcogen atom, were considered.
Gold phenolate complexes: Synthesis, structure, and reactivity
Ibrahim, Nada,Vilhelmsen, Mie Hojer,Pernpointner, Markus,Rominger, Frank,Hashmi, A. Stephen K.
, p. 2576 - 2583 (2013/06/26)
Seven different NHC gold(I) phenolate complexes were synthesized. Structural data, including X-ray crystal structure analyses, could be obtained for each of them. An investigation by computational chemistry, including NBO analysis, indicates three-center-four-electron hyperbonds among the carbene carbon, the gold atom, and the oxygen atom of the phenolate with an approximate 60:40 distribution of the bonding interaction in favor of the carbene-gold bond. The new class of complexes shows only moderate catalytic activity.
Synthesis of K[4-ROC6F4BF3] from potassium pentafluorophenyltrifluoroborate and O-nucleophiles
Shabalin, Anton Yu.,Adonin, Nicolay Yu.,Bardin, Vadim V.,Prikhod'Ko, Sergey A.,Timofeeva, Maria N.,Bykova, Maria V.,Parmon, Valentin N.
, p. 82 - 87 (2013/05/22)
A new route to potassium polyfluoroaryltrifluoroborates, K[4-ROC 6F4BF3], consisting in the nucleophilic alkoxydefluorination of K[C6F5BF3] with MOR (M = K, Na) in a polar aprotic solvent is suggested. Reaction of K[C 6F5BF3] with KO-t-Bu proceeds smoothly at 25 °C in DME, but the attempted alkoxydefluorination of K[C6F 5BF3] with other NaOR at 30 °C in DME failed. A series of K[4-ROC6F4BF3] (R = Me, Et, Pr, i-Pr, Bu, PhCH2) is prepared using the corresponding sodium alkoxides in DMF at 130 °C in 80-90% isolated yield. Salt K[4-CH2CHCH 2OC6F4BF3] is prepared at 100 °C whereas at 130 °C formation of 2,3,5,6-C6F4HOCH 2CHCH2 occurs. Salt K[4-PhOC6F 4BF3] is obtained in 82% yield using KOPh (2 equivalents) in DMSO at 130 °C.
