27073-41-2Relevant academic research and scientific papers
Steady-state kinetic analysis of human cholinesterases over wide concentration ranges of competing substrates
Mukhametgalieva, Aliya R.,Lushchekina, Sofya V.,Aglyamova, Aliya R.,Masson, Patrick
, (2021/10/22)
Substrate competition for human acetylcholinesterase (AChE) and human butyrylcholinesterase (BChE) was studies under steady-state conditions using wide range of substrate concentrations. Competing couples of substates were acetyl-(thio)esters. Phenyl acetate (PhA) was the reporter substrate and competitor were either acetylcholine (ACh) or acetylthiocholine (ATC). The common point between investigated substrates is that the acyl moiety is acetate, i.e. same deacylation rate constant for reporter and competitor substrate. Steady-state kinetics of cholinesterase-catalyzed hydrolysis of PhA in the presence of ACh or ATC revealed 3 phases of inhibition as concentration of competitor increased: a) competitive inhibition, b) partially mixed inhibition, c) partially uncompetitive inhibition for AChE and partially uncompetitive activation for BChE. This sequence reflects binding of competitor in the active centrer at low concentration and on the peripheral anionic site (PAS) at high concentration. In particular, it showed that binding of a competing ligand on PAS may affect the catalytic behavior of AChE and BChE in an opposite way, i.e. inhibition of AChE and activation of BChE, regardless the nature of the reporter substrate. For both enzymes, progress curves for hydrolysis of PhA at very low concentration (?Km) in the presence of increasing concentration of ATC showed that: a) the competing substrate and the reporter substrate are hydrolyzed at the same time, b) complete hydrolysis of PhA cannot be reached above 1 mM competing substrate. This likely results from accumulation of hydrolysis products (P) of competing substrate and/or accumulation of acetylated enzyme·P complex that inhibit hydrolysis of the reporter substrate.
Aerobic C?C Bond Cleavage Catalyzed by Whole-Cell Cultures of the White-Rot Fungus Dichomitus albidofuscus
Zhuk, Tatyana S.,Babkina, Valeriia V.,Zorn, Holger
, (2021/12/30)
Whole-cell cultures of the basidiomycetous white-rot fungus Dichomitus albidofuscus exhibit varying catalytic activity towards aromatic compounds depending on the growth stage. This study reveals the catalytic behavior of mature whole-cell cultures that effectively catalyze a C?C bond cleavage oxidizing toluene, benzaldehyde and acetophenone to phenol. The reaction products were analyzed by GC-MS and NMR techniques. To exclude the de novo formation of phenol by the fungus, its origin has been proven by bioconversion of benzaldehyde-d5. The key step involves an aerobic Baeyer-Villiger type rearrangement where the incorporation of oxygen into the product was confirmed based on isotope labelling experiments with 18O2. Intermediate esters were not found in reaction mixture presumably due to the detected esterase activity in the mycelium as well as in supernatant of the whole-cell cultures. As a result, the sequence of biocatalytic reactions catalyzed by D. albidofuscus for the degradation of toluene via C?C bond cleavage has been disclosed.
A highly efficient transformation from cumene to cumyl hydroperoxide via catalytic aerobic oxidation at room temperature and investigations into solvent effects, reaction networks and mechanisms
Chen, Chong,Ji, Lijun,Lu, Qiuting,Shi, Guojun,Yuan, Enxian,Zhou, Hongyu
, (2021/12/04)
Cumyl hydroperoxide (CHP) is an important intermediate for the production of phenol/acetone, but suffers from severe reaction conditions and a low yield industrially. Here, an efficient transformation from cumene to CHP was developed. Different solvents were modulated for cumene oxidation catalyzed by NHPI/Co, and reaction network and mechanisms were investigated methodically. Hexafluoroisopropanol (HFIP) markedly promoted the transformation from cumene to CHP compared to other solvents at room temperature. A cumene conversion high up to 64.3% were observed with a selectivity to CHP of 71.7%. The solvent HFIP exhibited a significant promotion on cumene oxidation due to its contribution to the enhancement of the concentration of PINO radicals. Moreover, cumyl, cumyl oxyl and methyl radicals were captured by TEMPO and analyzed by HRMS, and the reaction paths and mechanisms from cumene to products were inferred. The preparation method discovered in this work may open an access to the production of CHP.
An alternative route for the preparation of phenol: Decomposition of cyclohexylbenzene-1-hydroperoxide
Yang, Yufei,Zhang, Yadong
, p. 71 - 80 (2021/09/28)
In this work, a HPW/ZSM-5 catalyst was prepared by impregnating phosphotungstic acid (HPW) with carrier ZSM-5 zeolite and characterized by XRD, SEM, N2 adsorption/desorption isotherm, NH3-TPD, and FT-IR techniques. The catalytic performance of HPW/ZSM-5 was investigated by using the decomposition reaction of cyclohexylbenzene-1-hydroperoxide (CHBHP) to phenol and cyclohexanone. The conversion rate of CHBHP was up to 97.28%. In addition, the reusability test exhibited that the high durability HPW/ZSM-5 as the conversion rate of CHBHP only decreased by 3.11% after five runs. The kinetic study of the decomposition reaction indicated it was a primary reaction. The apparent activation energy of the decomposition reaction was 102.39?kJ·mol–1 in the temperature range of 45–60℃. All results indicate that the HPW/ZSM-5 catalyst has good performance and promising applications in acid catalyzed organic chemistry.
Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
Martos, Mario,Pastor, Isidro M.
, (2022/01/03)
Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
Coordination Polymers as a Functional Material for the Selective Molecular Recognition of Nitroaromatics and ipso-Hydroxylation of Arylboronic Acids
Rani, Pooja,Husain, Ahmad,Bhasin,Kumar, Girijesh
, (2021/12/06)
We report the synthesis and structural characterization of two coordination polymers (CPs), namely; [{Zn(L)(DMF)4} ? 2BF4]α (1) and [{Cd(L)2(Cl)2} ? 2H2O]α (2) (where L=N2,N6-di(pyridin-4-yl)naphthalene-2,6-dicarboxamide). Crystal packing of 1 reveals the existence of channels running along the b- and c-axis filled by the ligated DMF and lattice anions, respectively. Whereas, crystal packing of 2 reveals that the metallacycles of each 1D chain are intercalating into the groove of adjacent metallacycles resulting in the stacking of 1D loop-chains to form a sheet-like architecture. In addition, both 1 and 2 were exploited as multifunctional materials for the detection of nitroaromatic compounds (NACs) as well as a catalyst in the ipso-hydroxylation of aryl/heteroarylboronic acids. Remarkably, 1 and 2 showed high fluorescence stability in an aqueous medium and displayed a maximum 88% and 97% quenching efficiency for 4-NPH, respectively among all the investigated NACs. The mechanistic investigation of NACs recognition suggested that the fluorescence quenching occurred via electron as well as energy transfer process. Furthermore, the ipso-hydroxylation of aryl/heteroarylboronic acids in presence of 1 and 2 gave up to 99% desired product yield within 15 min in our established protocol. In both cases, 1 and 2 are recyclable upto five cycles without any significant loss in their efficiency.
Droplet Flow Assisted Electrocatalytic Oxidation of Selected Alcohols under Ambient Condition
Al Aqad, Khaled M.,Basheer, Chanbasha,Suliman, Mohammed A.
, (2022/01/11)
This study reports using a droplet flow assisted mechanism to enhance the electrocatalytic oxidation of benzyl alcohol, 2-phenoxyethanol, and hydroxymethylfurfural at room temperature. Cobalt phosphide (CoP) was employed as an active electrocatalyst to promote the oxidation of each of the individual substrates. Surface analysis of the CoP electrocatalyst using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), as well as electrochemical characterization, revealed that it had excellent catalytic activity for each of the substrates studied. The combined droplet flow with the continuous flow electrochemical oxidation approach significantly enhanced the conversion and selectivity of the transformation reactions. The results of this investigation show that at an electrolysis potential of 1.3 V and ambient conditions, both the selectivity and yield of aldehyde from substrate conversion can reach 97.0%.
Impact of oxygen vacancies in Ni supported mixed oxide catalysts on anisole hydrodeoxygenation
Ali, Hadi,Kansal, Sushil Kumar,Lauwaert, Jeroen,Saravanamurugan, Shunmugavel,Thybaut, Joris W.,Vandevyvere, Tom
, (2022/03/02)
The hydrodeoxygenation (HDO) activity of anisole has been investigated over Ni catalysts on mixed metal oxide supports containing Nb–Zr and Ti–Zr in 1:1 and 1:4 ratios. XRD patterns indicate the incorporation of Ti (or Nb) into the ZrO2 framewo
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.
Pyridazine N-Oxides as Photoactivatable Surrogates for Reactive Oxygen Species
Basistyi, Vitalii S.,Frederich, James H.
supporting information, p. 1907 - 1912 (2022/03/27)
A method for the photoinduced evolution of atomic oxygen from pyridazine N-oxides was developed. This underexplored oxygen allotrope mediates arene C-H oxidation within complex, polyfunctional molecules. A water-soluble pyridazine N-oxide was also developed and shown to promote photoinduced DNA cleavage in aqueous solution. Taken together, these studies highlight the utility of pyridazine N-oxides as photoactivatable O(3P) precursors for applications in organic synthesis and chemical biology.
