20237-92-7Relevant articles and documents
Bioinspired Catalytic Reduction of Aqueous Perchlorate by One Single-Metal Site with High Stability against Oxidative Deactivation
Liu, Jinyong,Ren, Changxu
, p. 6715 - 6725 (2021)
Reduction of perchlorate (ClO4-) with an active and stable catalyst is of great importance for environmental, energy, and space technologies. However, after the rate-limiting oxygen atom transfer (OAT) from inert ClO4-, the much more reactive ClOx- (x ≤ 3) intermediates can cause catalyst deactivation. The previous Re-Pd/C catalyst contained a [ReV(O)(hoz)2]+ site (Hhoz = 2-(2′-hydroxyphenyl)-2-oxazoline) and readily reduced ClO4-, but ClOx- intermediates led to rapid formation and hydrolysis of [ReVII(O)2(hoz)2]+. While microbes use delicate enzymatic machinery to survive the oxidative stress during ClO4- reduction, a synthetic catalyst needs a straightforward self-protective design. In this work, we introduced a methyl group on the ligand oxazoline moiety and achieved a substantial enhancement of catalyst stability without sacrificing the performance of ClO4- reduction. A suite of kinetics measurement, X-ray photoelectron spectroscopy characterization, reaction modeling, stopped-flow photospectrometry, and 1H NMR monitoring revealed the underlying mechanism. The most critical and unexpected effect of the methyl group is the deceleration (for 2 orders of magnitude) of OAT from ClO3- to [ReV(O)(Mehoz)2]+. However, the rate of OAT with ClO4- was not affected. The methyl group also slowed down the hydrolysis of [ReVII(O)2(Mehoz)2]+ and allowed the introduction of methoxy onto the phenolate moiety to further accelerate ClO4- reduction. With 1 atm H2 at 20 °C, the Re-Pd/C catalyst used [ReV(O)(MehozOMe)2]+ as the only reaction site to reduce multiple spikes of 10 mM ClO4- into Cl- without decomposition. This work showcases the significant effect of simple ligand modification in improving catalyst stability for high-performance ClO4- reduction.
Identification of Adenosine Deaminase Inhibitors by Metal-binding Pharmacophore Screening
Adamek, Rebecca N.,Ludford, Paul,Duggan, Stephanie M.,Tor, Yitzhak,Cohen, Seth M.
supporting information, p. 2151 - 2156 (2020/10/19)
Adenosine deaminase (ADA) is a human mononuclear Zn2+ metalloenzyme that converts adenosine to inosine. ADA is a validated drug target for cancer, but there has been little recent work on the development of new therapeutics against this enzyme. The lack of new advancements can be partially attributed to an absence of suitable assays for high-throughput screening (HTS) against ADA. To facilitate more rapid drug discovery efforts for this target, an in vitro assay was developed that utilizes the enzymatic conversion of a visibly emitting adenosine analogue to the corresponding fluorescent inosine analogue by ADA, which can be monitored via fluorescence intensity changes. Utilizing this assay, a library of ～350 small molecules containing metal-binding pharmacophores (MBPs) was screened in an HTS format to identify new inhibitor scaffolds against ADA. This approach yielded a new metal-binding scaffold with a Ki value of 26±1 μM.
OXAZOLINE COMPOUND, CROSSLINKER AND RESIN COMPOSITION
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, (2019/03/07)
PROBLEM TO BE SOLVED: To provide an oxazoline compound and trioxazoline compound optimal as crosslinkers for a wide range of uses, including a coating agent, ink, a film, a binder, and adhesive or the like. SOLUTION: The present invention provides an oxazoline compound represented by the following chemical formula, a trioxazoline compound obtained by trifunctionalizing the oxazoline compound represented by the following chemical formula, and a crosslinker and a resin composition using the oxazoline compound or the trioxazoline compound. In the formula, X is H or R-OH, R is a C1-4 linear or branched alkylene group. SELECTED DRAWING: None COPYRIGHT: (C)2019,JPO&INPIT
Configuration Control in the Synthesis of Homo- and Heteroleptic Bis(oxazolinylphenolato/thiazolinylphenolato) Chelate Ligand Complexes of Oxorhenium(V): Isomer Effect on Ancillary Ligand Exchange Dynamics and Implications for Perchlorate Reduction Catalysis
Liu, Jinyong,Wu, Dimao,Su, Xiaoge,Han, Mengwei,Kimura, Susana Y.,Gray, Danielle L.,Shapley, John R.,Abu-Omar, Mahdi M.,Werth, Charles J.,Strathmann, Timothy J.
, p. 2597 - 2611 (2016/03/19)
This study develops synthetic strategies for N,N-trans and N,N-cis Re(O)(LO-N)2Cl complexes and investigates the effects of the coordination spheres and ligand structures on ancillary ligand exchange dynamics and catalytic perchlorate reduction activities of the corresponding [Re(O)(LO-N)2]+ cations. The 2-(2′-hydroxyphenyl)-2-oxazoline (Hhoz) and 2-(2′-hydroxyphenyl)-2-thiazoline (Hhtz) ligands are used to prepare homoleptic N,N-trans and N,N-cis isomers of both Re(O)(hoz)2Cl and Re(O)(htz)2Cl and one heteroleptic N,N-trans Re(O)(hoz)(htz)Cl. Selection of hoz/htz ligands determines the preferred isomeric coordination sphere, and the use of substituted pyridine bases with varying degrees of steric hindrance during complex synthesis controls the rate of isomer interconversion. The five corresponding [Re(O)(LO-N)2]+ cations exhibit a wide range of solvent exchange rates (1.4 to 24,000 s-1 at 25°C) and different LO-N movement patterns, as influenced by the coordination sphere of Re (trans/cis), the noncoordinating heteroatom on LO-N ligands (O/S), and the combination of the two LO-N ligands (homoleptic/heteroleptic). Ligand exchange dynamics also correlate with the activity of catalytic reduction of aqueous ClO4- by H2 when the Re(O)(LO-N)2Cl complexes are immobilized onto Pd/C. Findings from this study provide novel synthetic strategies and mechanistic insights for innovations in catalytic, environmental, and biomedical research.
New sky-blue and bluish-green emitting Ir(III) complexes containing an azoline ancillary ligand for highly efficient PhOLEDs
Sarada, Ganguri,Sim, Bomi,Cho, Woosum,Yoon, Juho,Gal, Yeong-Soon,Kim, Jang-Joo,Jin, Sung-Ho
, p. 60 - 68 (2016/04/26)
Two Ir(III) complexes containing the chromophoric ancillary ligands 2-(4,5-dihydrooxazol-2-yl)phenol and 2-(1-ethyl-4,5-dihydro-1H-imidazol-2-yl)phenol, and a highly functionalized phenylpyridine derivative, 3-(4-(tert-butyl)pyridin-2-yl)-2,6-difluorobenzonitrile, as a cyclometalating ligand were designed and synthesized. The oxazoline/imidazoline heterocycle of the ancillary ligand has the effect of enhancing the metal to ligand charge transfer transition nature of the emitting excited state and the fluorine and cyano substituents on the ligand have enriched the intersystem crossings, as indicated by the experimental photoluminescence analysis. As a result, the oxazoline and imidazoline containing complexes exhibited high photoluminescence quantum yields of about >90% with bright sky-blue emission at 480 nm and bluish-green light at 495 nm, respectively, along with excellent thermal/morphological stability about 400 °C and good solubility, that make them suitable for both wet- and dry-processes. In particular, the phosphorescent OLEDs fabricated by a dry-process showed the maximum EQEs of 21.9% and 19.7% for the oxazoline and imidazoline containing complexes, respectively.
Bioinspired complex-nanoparticle hybrid catalyst system for aqueous perchlorate reduction: Rhenium speciation and its influence on catalyst activity
Liu, Jinyong,Choe, Jong Kwon,Wang, Yin,Shapley, John R.,Werth, Charles J.,Strathmann, Timothy J.
, p. 511 - 522 (2015/03/04)
A highly active catalyst for reduction of the inert water contaminant perchlorate (ClO4-) to Cl- with 1 atm H2 at 25 °C is prepared by noncovalently immobilizing the rhenium complex ReV(O)(hoz)2Cl (hoz = 2-(2′-hydroxyphenyl)-2-oxazoline) together with Pd0 nanoparticles on a porous carbon support. Like the Mo complex centers in biological oxyanion reductases, the immobilized Re complex serves as a single site for oxygen atom transfer from ClO4- and ClOx- intermediates, whereas Pd0 nanoparticles provide atomic hydrogen reducing equivalents to sustain redox cycling of the immobilized Re sites, replacing the more complex chain of electron transfer steps that sustain Mo centers within oxyanion reductases. An in situ aqueous adsorption method of immobilization was used to preserve the active ReV(O)(hoz)2 structure during bimetallic catalyst preparation and enable study of Re redox cycling and reactions with ClO4-. Heterogeneous reaction kinetics, X-ray photoelectron spectroscopy, and experiments with homogeneous model Re complexes are combined to obtain insights into the catalytic reaction mechanisms and the influence of Re speciation on catalyst reactivity with ClO4-. Redox cycling between hoz-coordinated ReV and ReVII species serves as the main catalytic cycle for ClO4- reduction. Under reducing conditions, approximately half of the immobilized hoz-coordinated ReV is further reduced to ReIII, which is not directly reactive with ClO4-. A small fraction of the hoz-coordinated ReVII species can dissociate to ReO4- and free hoz, which are then reductively reimmobilized as a less reactive mixture of ReV, ReIII, and ReI species. This study provides an example wherein highly active metal complexes that were originally developed for homogeneous organic phase catalysis can be incorporated into heterogeneous catalysts for practical environmental applications. Findings suggest a general blueprint for developing hybrid catalysts combining single-site transition metal complexes with hydrogen-activating metal nanoparticles.
Oxorhenium(V) complexes with phenolate-oxazoline ligands: Influence of the isomeric form on the O-atom-transfer reactivity
Schachner, J?rg A.,Terfassa, Belina,Peschel, Lydia M.,Zwettler, Niklas,Belaj, Ferdinand,Cias, Pawel,Gescheidt, Georg,M?sch-Zanetti, Nadia C.
, p. 12918 - 12928 (2015/02/19)
The bidentate phenolate-oxazoline ligands 2-(2′-hydroxyphenyl)-2-oxazoline (1a, Hoz) and 2-(4′,4′-dimethyl-3′,4′-dihydrooxazol-2′-yl)phenol (1b, Hdmoz) were used to synthesize two sets of oxorhenium(V) complexes, namely, [ReOCl2(L)(PPh3)] [L = oz (2a) and dmoz (2b)] and [ReOX(L)2] [X = Cl, L = oz (3a or 3a′); X = Cl, L = dmoz (3b); X = OMe, L = dmoz (4)]. Complex 3a′ is a coordination isomer (N,N-cis isomer) with respect to the orientation of the phenolate-oxazoline ligands of the previously published complex 3a (N,N-trans isomer). The reaction of 3a′ with silver triflate in acetonitrile led to the cationic compound [ReO(oz)2(NCCH3)](OTf) ([3a′](OTf)). Compound 4 is a rarely observed isomer with a trans-O=Re-OMe unit. Complexes 3a, 3a′, [3a′](OTf), and 4 were tested as catalysts in the reduction of a perchlorate salt with an organic sulfide as the O acceptor and found to be active, in contrast to 2a and 2b. A comparison of the two isomeric complexes 3a and 3a′ showed significant differences in activity: 87% 3a vs 16% 3a′ sulfoxide yield. When complex [3a′](OTf) was used, the yield was 57%. Density functional theory calculations circumstantiate all of the proposed intermediates with N,N-trans configurations to be lower in energy compared to the respective compounds with N,N-cis configurations. Also, no interconversions between N,N-trans and N,N-cis configurations are predicted, which is in accordance with experimental data. This is interesting because it contradicts previous mechanistic views. Kinetic analyses determined by UV-vis spectroscopy on the rate-determining oxidation steps of 3a, 3a′, and [3a′](OTf) proved the N,N-cis complexes 3a′ and [3a′](OTf) to be slower by a factor of ～4.
Living cationic ring-opening polymerization of 2-oxazolines initiated by rare-earth metal triflates
Hu, Fangyu,Xie, Shoulei,Jiang, Liming,Shen, Zhiquan
, p. 59917 - 59926 (2015/02/19)
The cationic ring-opening polymerization (CROP) of substituted 2-oxazolines using rare-earth metal triflates (RE(OTf)3) as initiator was investigated for the first time. In this work, we examined the polymerization characteristics of 2-ethyl-2-oxazoline (EtOx) initiated by Sc(OTf)3 under conventional thermal heating and microwave irradiation, and compared the respective outcomes with those obtained with the most frequently used initiator methyl tosylate (MeOTs). The results indicated that Sc(OTf)3 exhibits a higher catalytic efficiency to the EtOx polymerization than MeOTs under identical conditions. The controlled/living nature of the Sc(OTf)3-catalyzed CROP was confirmed by its linear first-order kinetics and the narrow molecular weight distribution of the resultant polymers as well as the block copolymerization of EtOx and 2-phenyl-2-oxazoline (PhOx). Based on in situ NMR spectroscopic studies and SEC analysis of PEtOx samples obtained from the control termination experiments, a possible initiating/propagating mechanism has been proposed for the living cationic ring-opening polymerization. Morever, this rare-earth catalytic system can also be applied to the ring-opening polymerization of some sterically hindered or aryl-substituted 2-oxazolines.
Transformation of anionically activated trifluoromethyl groups to heterocycles under mild aqueous conditions
Qiao, Jennifer X.,Wang, Tammy C.,Hu, Carol,Li, Jianqing,Wexler, Ruth R.,Lam, Patrick Y. S.
supporting information; experimental part, p. 1804 - 1807 (2011/06/19)
The (hetero)aromatic trifluoromethyl group is present in many biologically active molecules and is generally considered to be chemically stable. In this paper, a convenient one-step synthesis of C-C linked aryl-heterocycles or heteroaryl-heterocycles in good to excellent yields via the reaction of anionically activated trifluoromethyl groups with amino nucleophiles containing a second NH, OH, or SH nucleophile in 1 N sodium hydroxide is reported. The method has high functional group tolerability and is potentially useful in parallel synthesis.
Synthesis of 2-oxazolines via boron esters of N-(2-hydroxyethyl) amides
Ilkgul, Baris,Gunes, Deniz,Sirkecioglu, Okan,Bicak, Niyazi
experimental part, p. 5313 - 5315 (2010/11/03)
A new, convenient, one-pot process is presented for the synthesis of 2-oxazolines in high yields (75-94%) via boron esters of N-(2-hydroxyethyl) amides. The procedure involves thermolysis of the boron esters at 240-260 °C, in the presence of solid CaO as an acid scavenger and allows the preparation of oxazolines from hydroxyethyl amides of aliphatic and aromatic monocarboxylic acids.
