150-76-5Relevant articles and documents
Description of Solvent Dependence of Rate Constants in Terms of Pairwise Group Gibbs Function Interaction Parameters. Medium Effects for Hydrolysis of p-Methoxyphenyl Dichloroacetate in Aqueous Solutions Containing Urea and Alkyl-Substituted Ureas
Blokzijl, Wilfried,Engberts, Jan B. F. N.,Jager, Jan,Blandamer, Michael J.
, p. 6022 - 6027 (1987)
Rate constants for neutral hydrolysis of p-methoxyphenyl dichloroacetate in aqueous solutions are sensitive to the molarity of added urea and alkyl-substituted ureas.These dependences are considered in the light of pairwise Gibbs function parameters describing interaction between solutes in aqueous solutions.In the next stage these interactions are examined by using the Savage-Wood additivity principle for pairwise group interaction parameters involving organic solutes and both initial and transition states for the hydrolysis reaction.The basis of the approach is described showing how kinetic and thermodynamic data are drawn together and used to comment on mechanisms of reaction in aqueous solutions.For the hydrolysis of the dichloroacetate ester, we account for the observed dependence of rate constant on solvent in terms of a reaction that is second order with respect to water, where the transition state exposes three OH groups to the aqueous solution, and in terms of derived group interaction parameters involving these OH groups and both CH2 and CONH groups in added solutes.
Kinetics of hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in binary water-cosolvent mixtures; the role of solvent activity and solute-solute interactions
Rispens, Theo,Cabaleiro-Lago, Celia,Engberts, Jan B. F. N.
, p. 597 - 602 (2005)
Rate constants are reported for the pH-independent hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in aqueous solution as a function of the concentration of added cyanomethane (acetonitrile), polyethylene glycol (PEG 400) and tetrahydrofuran (THF). The concentration of water was varied between ca. 25 and 55.5 M. It was found that the variation in water activity yields only a minor contribution to the observed variation in rate constants. Interestingly, for both cyanomethane and PEG 400 log(k) varies approximately linearly with the molar concentration of water. Medium effects in highly aqueous solutions ([H2O] > 50 M) of ethanol, 1-propanol, 2-propanol, 1-butanol and 2-methyl-2-propanol have also been determined. Unexpectedly, in this concentration range the alcohols induce significantly smaller effects per unit volume than cyanomethane. The present results are discussed in terms of pairwise interaction parameters. Isobaric activation parameters have been determined and reveal remarkable differences in the nature of the induced medium effects.
Novel photo-fragmentation of 3,3,6,6-tetra(p-methoxyphenyl)-1,2-dioxane through a C-O bond cleaved 1,6-diradical intermediate
Kamata, Masaki,Tanaka, Takehito,Kato, Mitsuaki
, p. 8181 - 8184 (1996)
Photolysis and thermolysis of 3,3,6,6-tetraaryl-1,2-dioxanes were investigated. The photolysis of 3,3,6,6-tetra(p-methoxyphenyl)-1,2-dioxane afforded 1,4,4-tri(p-methoxyphenyl)-3-buten-1-one and p-methoxyphenol through a novel C-O bond cleaved 1,6-diradical intermediate, while the thermolysis mainly afforded the expected decomposition product 4,4'-dimethoxybenzophenone through an O-O bond cleaved 1,6-dioxy diradical intermediate.
Efficiency of 2.45 and 5.80 GHz microwave irradiation for a hydrolysis reaction by thermostable β-Glucosidase HT1
Nagashima, Izuru,Sugiyama, Jun-Ichi,Sakuta, Tomomi,Sasaki, Masahide,Shimizu, Hiroki
, p. 758 - 760 (2014)
Microwave irradiation at different frequencies gave unique results for the hydrolyses of glycosyl bonds by β-Glucosidase HT1. With the observed relative complex permittivity data for the reaction buffer, 2.45 GHz microwave radiation affected both waters and ions, while 5.80 GHz only affected waters. We, here, propose that would be one of the unique "microwave nonthermal effects".
Burkhardt,Ford,Singleton
, p. 17,19 (1936)
Aryldiazonium Salts as Photo-affinity Labelling Reagents for Proteins
Kieffer, Brigitte L.,Goeldner, Maurice Ph.,Hirth, Christian G.
, p. 398 - 399 (1981)
Aryldiazonium tetrafluoroborates, substituted in the para-position by electron donating substituents, are potential photo-affinity labelling reagents for proteins and after light activation irreversibly inhibit acetylcholinesterase; using radiolabelled reagent, the inactivation is shown to be approximately stoicheiometric.
Microbial Oxidation of Racemic vic-Diols. Synthesis of (R)- and (S)-α-Hydroxypropiophenones
Ohta, Hiromichi,Yamada, Hiroshi,Tsuchihashi, Gen-ichi
, p. 2325 - 2326 (1987)
Both enantiomers of 2-hydroxy-1-phenyl-1-propanone have been syntyesized by microbial oxidation of racemic syn- and anti-1-phenylpropane-1,2-diols, which are available from 1-phenylpropyne.
Rate parameter changes by added albumin in the microsomal oxidative demethylation of deuteriated and non-deuteriated 4-methoxyanisole
Masuda, Masatoshi,Kishimoto, Daisuke,Kurihara, Norio
, p. 806 - 810 (1996)
Bovine serum albumin (BSA) added to the reaction medium for the oxidative demethylation of 4-methoxyanisole and its 'di-CD3' isotopomer ([d6]methoxyanisole), when catalyzed by liver microsomes from untreated rats, decreased the K(m) values and increased the V(max)/K(m)(= V/K) values. The V(max) values were not markedly altered. The values for the deuterium isotope effect on V(max) and V/K for the reaction with this isotopomer were between 2.2 and 2.8, and that on K(m) was close to unity. The magnitude of the isotope effect was not significantly changed by adding BSA. The intramolecular isotope effect with [mono-CD3]4-methoxyanisole ([d3]methoxyanisole) in liver microsomes from untreated rats was between 10.3 and 10.8, which was not significantly changed by BSA. Liver microsomes from rats treated with phenobarbital resulted in the intramolecular isotope effect value in the absence of BSA being between 7.2 and 9.1, which was not significantly altered by BSA. Based on these data, the calculated apparent rate constant for the enzyme-substrate complex formation was markedly increased by up to about 1.9- and 3.5-fold by 1% and 2% of BSA added, respectively.
Stereoselective umpolung tandem addition of heteroatoms to phenol
Todd, Michael A.,Sabat, Michal,Myers, William H.,Smith, Timothy M.,Harman, W. Dean
, p. 6906 - 6907 (2008)
Upon coordination to {TpW(PMe3)(NO)}, phenol tautomerizes to a cyclohexadienone (a 2H-phenol). The uncoordinated, nonaromatic double bond of this ligand undergoes stepwise addition of electrophiles followed by nucleophiles to produce 4,5-disubstituted cyclohexenone complexes. The metal stabilizes the intermediate cationic ligand and sterically blocks one face of the ligand, resulting in a high degree of stereo- and regiocontrol. These substituted cyclohexenones are readily liberated from the metal by oxidative decomplexation. Copyright
The mechanisms of hydrolysis of N-alkyl O-arylthioncarbamate esters
Humeres, Eduardo,De Souza, Eduardo P.,Debacher, Nito A.
, p. 915 - 924 (2010)
The hydrolysis of N-ethyl O-p-methoxyphenylthioncarbamate (EMeOT) at 50°-C was studied in the range of HXo S3.6 to HS 13.7. The pH-rate profile showed that the hydrolysis occurred through specific acid catalysis at pH 3. The excess acidity plot against X was linear with slope 0.93, and the Bunnett-Olsen coefficient was 0.07. The acid hydrolysis occurred by an A1 mechanism. The basic hydrolysis of EMeOT can be explained if the mechanism is E1cb. At pH >3 the rate constants increased, reaching a constant value indicating that the expulsion of the aryloxy is not concerted. The neutral species hydrolyzed with general base catalysis with Bronsted β=.63±0.07. Water acted as a general base catalyst with (pseudo-) first-order rate constant kN=(2.6±0.2)×10-8 s-1, and inverse kinetic solvent isotope effect of kD o =kHo= 2:76 consistent with a transfer of the proton at a late transition state, as also supported by the highly negative entropy of activation (-31 cal K-1 mol-1). The polynomial expression of the proton inventory curve presented a minimum of the standard deviations that favors the assumption that there are three active protons. The N to O proton transfer to the water molecule forms an incipient hydron. The fractionation factor of the TS of the protons indicated that the hydron is ca. 68% developed at the transition state. Copyright
Photohomolysis and Photoheterolysis in Aryl Sulfonates and Aryl Phosphates
Bonesi, Sergio,Protti, Stefano,Fagnoni, Maurizio
, p. 6315 - 6323 (2021)
The photochemical behaviour of selected aryl sulfonates and phosphates (ArOX) in polar and nonpolar media has been investigated by laser flash photolysis (LFP) experiments. Two main pathways have been identified, namely the photohomolysis of the ArO?X bon
Are phosphines viable ligands for Pd-Catalyzed aerobic oxidation reactions? Contrasting insights from a survey of six reactions
Tereniak, Stephen J.,Landis, Clark R.,Stahl, Shannon S.
, p. 3708 - 3714 (2018)
Phosphines are the broadest and most important class of ligands in homogeneous catalysis, but they are typically avoided in Pd-catalyzed aerobic oxidation reactions because of their susceptibility to oxidative degradation. Recent empirical reaction-development efforts have led to a growing number of Pd/phosphine catalyst systems for aerobic oxidative coupling reactions, but few of these studies have assessed the fate of the phosphine ligand. Here, we assess six different oxidative coupling reactions, including the homocoupling of boronic acids, amino- and alkoxycarbonylation reactions, intramolecular C-H annulation, and enantioselective Fujiwara-Moritani C-C coupling. The fate and role of the phosphine, analyzed by 31P NMR spectroscopy throughout the reaction time course in each case, varies in different reactions. In one case, the phosphine has an inhibitory effect and leads to lower selectivity relative to ligand-free conditions. In other cases, the phosphine ligands have a beneficial effect on the reaction but undergo oxidative decomposition in parallel with productive catalytic turnover. Inclusion of MnO2 in one of the reactions slows phosphine oxidation by catalyzing disproportionation of H2O2 and thereby supports productive catalytic turnover. Negligible oxidation of the chiral phosphine (S,S)-chiraphos is observed during the enantioselective C-C coupling reaction, due to strong chelation of the ligand to PdII. The results of this study suggest that phosphines warrant broader attention as ligands for Pd-catalyzed aerobic oxidation reactions, particularly by implementing strategies identified for ligand stabilization.
Stereodivergent Synthesis of β-Heteroatom-Substituted Vinyl-silanes by Sequential Silylzincation-Copper(I)-Mediated Electrophilic- Substitution
Fopp, Carolin,Isaac, Kevin,Romain, Elise,Chemla, Fabrice,Ferreira, Franck,Jackowski, Olivier,Oestreich, Martin,Perez-Luna, Alejandro
, p. 724 - 735 (2017)
Sulfur-, oxygen-, and phosphorus-substituted terminal alkynes undergo regio- and stereoselective silylzincation by reaction with (Me2PhSi)2Zn, (Me3Si)3SiH/Et2Zn or [(Me3Si)3Si]2Zn/Et2Zn. The addition across the C-C triple bond always occurs with β-regioselectivity but the stereoselectivity is tunable: (Me2PhSi)2Zn for cis and (Me3Si)3SiH/-Et2Zn or [(Me3Si)3Si]2Zn/Et2Zn for trans. The procedures making use of the zinc reagents (Me2PhSi)2Zn and [(Me3Si)3Si]2Zn can be combined in one-pot with a subsequent stereoretentive copper(I)-mediated electrophilic substitution of the intermediate C(sp2)-Zn bond. These stereodivergent protocols offer a regio- and stereoselective access to trisubstituted vinylsilanes decorated with sulfur-, oxygen-, and phosphorus substituents with either double-bond geometry.
Engineering a highly improved porous photocatalyst based on Cu2O by a synergistic effect of cation doping of Zn and carbon layer coating
Yuan, Yusheng,Sun, Li-Ming,Gao, Hao,Mo, Sha,Xu, Tianyi,Yang, Lei,Zhan, Wen-Wen
, p. 16010 - 16015 (2020)
Zn-doped cuprous oxide (Cu2O) nanoparticles coated by carbon layers (Zn/Cu2O@C) have been obtained via a bimetallic MOF (Zn/Cu-MOF-199) as the sacrificial precursor. Originated from the octahedral morphology of Zn/Cu-MOF-199, the as-synthesized Zn/Cu2O@C shows a porous octahedron structure. The obtained Zn/Cu2O@C can afford the following merits. (1) The cation doping of Zn inside Cu2O can enhance the light absorption by introducing impurity energy levels and facilitate the separation of photoinduced electrons and holes. (2) The coating of a carbon layer in Zn/Cu2O@C can also efficiently enhance the separation efficiency of photoinduced charge carriers. (3) The porous structure of Zn/Cu2O@C can provide increased active sites. Therefore, these merits lead to the highly improved photocatalytic activities toward various chemical reactions. In addition, the fully coated carbon layer can facilitate the cycle stability of Zn/Cu2O@C in the photocatalytic processes.
A Nanographene-Based Two-Dimensional Covalent Organic Framework as a Stable and Efficient Photocatalyst
Addicoat, Matthew A.,Bonn, Mischa,Chen, Qiang,Fu, Shuai,Graf, Robert,Hanayama, Hiroki,Jin, Enquan,Landfester, Katharina,Müllen, Klaus,Narita, Akimitsu,Wang, Hai I.,Wei, Wenxin,Zhang, Kai A. I.
supporting information, (2021/12/22)
Synthesis of covalent organic frameworks (COFs) with desirable organic units furnishes advanced materials with unique functionalities. As an emerging class of two-dimensional (2D) COFs, sp2-carbon-conjugated COFs provide a facile platform to build highly stable and crystalline porous polymers. Herein, a 2D olefin-linked COF was prepared by employing nanographene, namely, dibenzo[hi,st]ovalene (DBOV), as a building block. The DBOV-COF exhibits unique ABC-stacked lattices, enhanced stability, and charge-carrier mobility of ≈0.6 cm2 V?1 s?1 inferred from ultrafast terahertz photoconductivity measurements. The ABC-stacking structure was revealed by the high-resolution transmission electron microscopy and powder X-ray diffraction. DBOV-COF demonstrated remarkable photocatalytic activity in hydroxylation, which was attributed to the exposure of narrow-energy-gap DBOV cores in the COF pores, in conjunction with efficient charge transport following light absorption.
A highly photosensitive covalent organic framework with pyrene skeleton as metal-free catalyst for arylboronic acid hydroxylation
Chen, Ying,Huo, Jianqiang,Zhang, Yubao
, (2022/03/16)
Covalent organic frameworks (COFs) have been widely utilized in metal-free photocatalytic synthesis base on their excellent properties such as super conjugation, porosity and stability. In this work, we synthesized a new COF material using 1,3,6,8-Tetrakis (p-formylphenyl)pyrene (TFPPy) and 2,2′-Dimethylbenzidine (DMBZ) as basic units through Schiff base condensation reaction. The new COF (TF-DM COF) was applied as metal-free catalyst for hydroxylation of arylboronic acids. The results indicated that the extended π conjugation of COFs enhanced the absorption of visible light, and the large porosity (BET surface area: 113.782 m2g?1) accelerated the reaction rate. Good recyclability enables it with multiple applications, which result in a great reducing of the cost. This study reports that TF-DM COF has a broad application prospect as a new generation of metal-free photocatalysts for organic conversions.
