615-90-7Relevant articles and documents
Pseudosymmetry in 2,5-dimethyl-1,4-benzenediol
Gainsford,Miller,Yorke,Rae
, p. 1673 - 1675 (1997)
The title compound, C8H10O2, was prepared from di-acetyl by a high temperature and pressure reaction. Pseudosymmetry in the structure results in diffraction symmetry enhancement for half the reflections and the possibility of twinning and stacking faults. The structure consists of two independent but pseudosymmetrically-related P21/c substructures, each having centrosymmetric molecules on centres of inversion which are strongly hydrogen bonded to symmetry-related molecules to form layers perpendicular to c*, The structure may be described as an occupancy modulation, ordering a disordered parent structure in Pnma symmetry to form, upon change of axes, the P21c structure reported. The hydroxyl H atoms have two site options corresponding to alternative hydrogen-bonding patterns and the methyl H atoms in one substructure are rotationally disordered.
Magnetic Resonance Studies of Cation Radicals from Chromans
Smith, Ian M.,Sutcliffe, Leslie H.,Wiesner, Stefan,Lubitz, Wolfgang,Kurreck, Harry
, p. 3021 - 3036 (1984)
N.m.r. spectroscopy has been used to study the electron-exchange reaction between the substrate-radical pairs of 2,3,4,7,8,9-hexahydro-2,2,5,7,7,10-hexamethylbenzodipyran, 2,3,4,5,6,7-hexahydro-2,2,7,7,9,10-hexamethylbenzodipyran and 2,3,6,7-tetrahydro-2,2,4,6,6,8-hexamethylbenzodifuran and their cation radicals.The rate constants and energetics of activation of the reactions have been determined, along with absolute signs of the averaged proton hyperfine coupling constants.ENDOR and TRIPLE measurements provided accurate values of the individual coupling constants and their relative signs: the n.mr. and ENDOR data taken together gaved complete assignment.
Aqueous solubility of organic compounds for flow battery applications: Symmetry and counter ion design to avoid low-solubility polymorphs
Bereczki, Laura,Garcia, Sergio Navarro,Kónya, Dénes,Yang, Xian
, (2021/05/31)
Flow batteries can play an important role as energy storage media in future electricity grids. Organic compounds, based on abundant elements, are appealing alternatives as redox couples for redox flow batteries. The straightforward scalability, the independence of material sources, and the potentially attractive price motivate researchers to investigate this technological area. Four different benzyl-morpholino hydroquinone derivatives were synthesized as potential redox active species. Compounds bearing central symmetry were shown to be about an order of magnitude less soluble in water than isomers without central symmetry. Counter ions also affected solubility. Perchlorate, chlorate, sulfate and phosphate anions were investigated as counter ions. The formations of different polymorphs was observed, showing that their solubility is not a function of their structure. The kinetics of the transformation can give misleading solubility values according to Ostwald’s rule. The unpredictability of both the kinetics and the thermodynamics of the formation of polymorphs is a danger for new organic compounds designed for flow battery applications.
Reduction of Activated Alkenes by PIII/PV Redox Cycling Catalysis
Longwitz, Lars,Werner, Thomas
supporting information, p. 2760 - 2763 (2020/02/05)
The carbon–carbon double bond of unsaturated carbonyl compounds was readily reduced by using a phosphetane oxide catalyst in the presence of a simple organosilane as the terminal reductant and water as the hydrogen source. Quantitative hydrogenation was observed when 1.0 mol % of a methyl-substituted phosphetane oxide was employed as the catalyst. The procedure is highly selective towards activated double bonds, tolerating a variety of functional groups that are usually prone to reduction. In total, 25 alkenes and two alkynes were hydrogenated to the corresponding alkanes in excellent yields of up to 99 %. Notably, less active poly(methylhydrosiloxane) could also be utilized as the terminal reductant. Mechanistic investigations revealed the phosphane as the catalyst resting state and a protonation/deprotonation sequence as the crucial step in the catalytic cycle.
Can Donor Ligands Make Pd(OAc)2a Stronger Oxidant? Access to Elusive Palladium(II) Reduction Potentials and Effects of Ancillary Ligands via Palladium(II)/Hydroquinone Redox Equilibria
Bruns, David L.,Musaev, Djamaladdin G.,Stahl, Shannon S.
supporting information, p. 19678 - 19688 (2020/12/18)
Palladium(II)-catalyzed oxidation reactions represent an important class of methods for selective modification and functionalization of organic molecules. This field has benefitted greatly from the discovery of ancillary ligands that expand the scope, reactivity, and selectivity in these reactions; however, ancillary ligands also commonly poison these reactions. The different influences of ligands in these reactions remain poorly understood. For example, over the 60-year history of this field, the PdII/0 redox potentials for catalytically relevant Pd complexes have never been determined. Here, we report the unexpected discovery of (L)PdII(OAc)2-mediated oxidation of hydroquinones, the microscopic reverse of quinone-mediated oxidation of Pd0 commonly employed in PdII-catalyzed oxidation reactions. Analysis of redox equilibria arising from the reaction of (L)Pd(OAc)2 and hydroquinones (L = bathocuproine, 4,5-diazafluoren-9-one), generating reduced (L)Pd species and benzoquinones, provides the basis for determination of (L)PdII(OAc)2 reduction potentials. Experimental results are complemented by density functional theory calculations to show how a series of nitrogen-based ligands modulate the (L)PdII(OAc)2 reduction potential, thereby tuning the ability of PdII to serve as an effective oxidant of organic molecules in catalytic reactions.
1-Methyl-1,4-cyclohexadiene as a Traceless Reducing Agent for the Synthesis of Catechols and Hydroquinones
Baschieri, Andrea,Amorati, Riccardo,Valgimigli, Luca,Sambri, Letizia
, p. 13655 - 13664 (2019/10/28)
Pro-aromatic and volatile 1-methyl-1,4-cyclohexadiene (MeCHD) was used for the first time as a valid H-atom source in an innovative method to reduce ortho or para quinones to obtain the corresponding catechols and hydroquinones in good to excellent yields. Notably, the excess of MeCHD and the toluene formed as the oxidation product can be easily removed by evaporation. In some cases, trifluoroacetic acid as a catalyst was added to obtain the desired products. The reaction proceeds in air and under mild conditions, without metal catalysts and sulfur derivatives, resulting in an excellent and competitive method to reduce quinones. The mechanism is attributed to a radical reaction triggered by a hydrogen atom transfer from MeCHD to quinones, or, in the presence of trifluoroacetic acid, to a hydride transfer process.
A Quencher-Fluorophore-Type Probe for Detection and Imaging of NADPH in Human Breast Cancer Cells
Yu, Geunhyeok,Kim, Sungryung,Bae, Se Won,Yeo, Woon-Seok
supporting information, p. 807 - 811 (2019/08/12)
A new fluorogenic trimethyl lock quinone (TLQ) derivative, designated as the quencher-TLQ-fluorophore-type probe (Q-TLQ-F), was developed for selective detection of nicotinamide adenine dinucleotide phosphate (NADPH). By taking advantage of the well-known facile intramolecular ring cyclization reaction (δ-lactonization) of TLQ that can release a reporter molecule upon reduction, Q-TLQ-F was successfully applied for the detection of physiological NADPH generated by glucose-6-phosphate dehydrogenase in human breast cancer MDA-MB-231 cells.
Reactivity of iPrPCPIrH4 with para-benzoquinones
Wilklow-Marnell, Miles,Brennessel, William W.,Jones, William D.
, p. 209 - 214 (2017/11/24)
In the interest of investigating new hydrogen acceptors for pincer–iridium catalyzed dehydrogenations with the ability to be catalytically recycled, a series of para-benzoquinones have been reacted with iPrPCPIrH4 in various solvents and conditions. Preliminary results indicate that a wide range of quinones are capable of dehydrogenating iPrPCPIrH4, and that several turn-overs in alcohol dehydrogenation by iPrPCPIr are possible at room temperature using benzoquinone acceptors. However, strong acceptor–catalyst interactions are inhibitory toward catalysis when the acceptor is used in excess. A new class of (bis)-η2 pi-adducts, formed between iPrPCPIr and benzoquinones, nicknamed “barber-chairs”, has been identified and 3 examples have been characterized.
Metabolism of the Strobilurin Fungicide Mandestrobin in Wheat
Ando, Daisuke,Fujisawa, Takuo,Katagi, Toshiyuki
, p. 10154 - 10162 (2018/10/02)
The metabolic fate of a new fungicide, mandestrobin, labeled with 14C at the phenoxy or benzyl ring was examined in wheat after a single spray application at 300 g/ha. Mandestrobin penetrated into foliage over time, with both radiolabels showing similar 14C distribution in wheat, and 2.8-3.3% of the total radioactive residue remained on the surface of straw at the final harvest. In foliage, mandestrobin primarily underwent mono-oxidation at the phenoxy ring to produce 4-hydroxy or 2-/5-hydroxymethyl derivatives, followed by their subsequent formation of malonylglucose conjugates. In grain, the cleavage of its benzyl phenyl ether bond was the major metabolic reaction, releasing the corresponding alcohol derivative, while the counterpart 2,5-dimethylphenol was not detected. The constant RS enantiomeric ratio of mandestrobin showed its enantioselective metabolism to be unlikely on/in wheat.
One-Pot Synthesis to Quinone-Based Diaza[3.3]cyclophanes
Stahlhofen, Jana Marie,Schollmeyer, Dieter,Waldvogel, Siegfried R.
, p. 7226 - 7230 (2017/10/18)
A simple one-pot synthesis to [3.3]cyclophanes that involves quinone moieties was found. The protocol tolerates a variety of amines that include aliphatic and aromatic structures with different functional groups, such as hydroxy groups, amides, and terminal double and triple bonds. The straightforward synthesis can be performed by a twofold N-alkylation reaction with 2,5-bis(bromomethyl)-3,6-dimethyl-1,4-benzoquinone (1). Neither anhydrous nor inert conditions are required. Various amines can be employed without any activating groups, several functionalities at end groups are tolerated, and the cyclophanes generated can be easily modified or embedded into larger molecular architectures. The redox-active nature of these cyclophanes allows their use in electron-transfer processes.
