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111.
Mijeong Han Huimin Bie David E. Nikles Garry W. Warren 《Journal of polymer science. Part A, Polymer chemistry》2000,38(16):2893-2899
A new diamine monomer was synthesized by the Michael addition of 4,4′‐methylene dianiline with 1,4‐benzoquinone. The monomer was condensed with 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride to give a polyamic acid that was soluble in NMP. The polyamic acid was cast onto iron and thermally imidized to yield the amine–quinone polyimide (AQPI‐2). AQPI‐2 had a thermal decomposition temperature of 540 °C (10% TGA weight loss in N2) and a glass transition at 292 °C, values typical of polyimides. The degradation of the coating on iron after exposure to 0.1 M NaCl electrolyte was followed by electrochemical impedance spectroscopy. Under these conditions a conventional polyimide failed after 3 days exposure, while AQPI‐2 survived more than 24 days exposure. The adhesive bond between the amine–quinone polyimide and the iron surface was so strong that it could not be broken by the electrolyte. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2893–2899, 2000 相似文献
112.
Congjun Yu Frederic W. Patureau 《Angewandte Chemie (International ed. in English)》2019,58(51):18530-18534
A metal free and highly regioselective oxidative arylation reaction of fluorophenols is described. The relative position of the fluoride leaving group (i.e., ortho or para) controls the 1,2 or 1,4 nature of the arylated quinone product, lending versatility and generality to this oxidative, defluorinative, arylation concept. 相似文献
113.
Dr. Yvonne Abel Dr. Ivan Vlassiouk Dr. Enno Lork Prof. Dr. Sergei Smirnov Prof. Dr. Marat R. Talipov Prof. Dr. Franz-Peter Montforts 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17120-17127
In donor–acceptor dyads undergoing photoinduced electron transfer (PET), a direction or pathway for electron movement is usually dictated by the redox properties and the separation distance between the donor and acceptor subunits, while the effect of symmetry is less recognized. We have designed and synthesized two isomeric donor–acceptor assemblies in which electronic coupling between donor and acceptor is altered by the orbital symmetry control with the reorganization energy and charge transfer exothermicity being kept unchanged. Analysis of the optical absorption and luminescence spectra, supported by the DFT and TD-DFT calculations, showed that PET in these assemblies corresponds to the Marcus inverted region (MIR) and has larger rate for isomer with weaker electronic coupling. This surprising observation provides the first experimental evidence for theoretically predicted adiabatic suppression of PET in MIR, which unambiguously controlled solely by symmetry. 相似文献
114.
Dr. Anthonius H. J. Engwerda Dr. Hugo Meekes Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Floris P. J. T. Rutjes Prof. Dr. Elias Vlieg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9639-9642
Chiral molecules exhibiting a quinone and/or hydroquinone moiety are ubiquitous in natural products and small molecule drugs. Herein, we describe a chiral quinone-hydroquinone molecule that racemizes through a reversible redox reaction. Using a combined computational and experimental approach, we show that this racemization proceeds via an intermolecular reaction mechanism. Starting from two achiral reactants, this molecule could be obtained in enantiopure form using Viedma ripening. 相似文献
115.
116.
Catalytic Asymmetric Addition of Meldrum’s Acid,Malononitrile, and 1,3‐Dicarbonyls to ortho‐Quinone Methides Generated In Situ Under Basic Conditions 下载免费PDF全文
Lorenzo Caruana Martina Mondatori Vasco Corti Sara Morales Prof. Andrea Mazzanti Prof. Mariafrancesca Fochi Prof. Luca Bernardi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6037-6041
A new approach to the utilization of highly reactive and unstable ortho‐quinone methides (o‐QMs) in catalytic asymmetric settings is presented. The enantioselective reactions are catalysed by bifunctional organocatalysts, and the o‐QM intermediates are formed in situ from 2‐sulfonylalkyl phenols through base‐promoted elimination of sulfinic acid. The use of mild Brønsted basic conditions for transiently generating o‐QMs in catalytic asymmetric processes is unprecedented, and allows engaging productively in the reactions nucleophiles such as Meldrum’s acid, malononitrile and 1,3‐dicarbonyls. The catalytic transformations give new and general entries to 3,4‐dihydrocoumarins, 4H‐chromenes and xanthenones. These frameworks are recurring structures in natural product and medicinal chemistry, as testified by the formal syntheses of (R)‐tolterodine and (S)‐4‐methoxydalbergione from the catalytic adducts. 相似文献
117.
Asymmetric anionic polymerizations of 7‐(o‐substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methides: Electrostatic interaction and steric,inductive, and resonance effects of the ortho‐substituent on the optical activity 下载免费PDF全文
Takahiro Uno Shuhei Yamamoto Atsushi Yamane Masataka Kubo Takahito Itoh 《Journal of polymer science. Part A, Polymer chemistry》2017,55(6):1048-1058
7‐(o‐Substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methides which have an electron‐donating methoxy‐(o‐OMe, 2a ) and methyl‐ (o‐Me, 2b ) substituents or an electron‐withdrawing cyano‐ (o‐CN, 2c ) and trifluoromethyl‐ (o‐CF3, 2d ) substituents at the ortho‐position of the aromatic ring and 7‐(m‐substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methide with an electron‐withdrawing trifluoromethyl‐ (m‐CF3, 2e ) substituent at the meta‐position of the aromatic ring were synthesized, and their asymmetric anionic polymerizations using the complex of lithium 4‐isopropylphenoxide with (?)‐sparteine were carried out in toluene at 0 °C. The polymers with negative optical activity were obtained for all of five monomers, and their specific rotation values largely changed depending upon the substituents of the monomers. On the basis of the comparison of various substituents effects, it was found that the specific rotation of obtained polymers is significantly affected by the electronic effects such as inductive and resonance effects rather than the steric and electrostatic effects of the substituent. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1048–1058 相似文献
118.
《Journal of computational chemistry》2017,38(18):1612-1621
Redox potentials are essential to understand biological cofactor reactivity and to predict their behavior in biological media. Experimental determination of redox potential in biological system is often difficult due to complexity of biological media but computational approaches can be used to estimate them. Nevertheless, the quality of the computational methodology remains a key issue to validate the results. Instead of looking to the best absolute results, we present here the calibration of theoretical redox potential for quinone derivatives in water coupling QM + MM or QM/MM scheme. Our approach allows using low computational cost theoretical level, ideal for long simulations in biological systems, and determination of the uncertainties linked to the calculations. © 2017 Wiley Periodicals, Inc. 相似文献
119.
A novel coordination polymer [Ba2(AQTC)(H2O)3]n(1, H4 AQTC = anthraquinone-1,4,5,8-tetracarboxylic acid) has been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. Two quinone oxygen atoms and all carboxylate oxygen atoms of AQTC4- are involved in coordination. Two equivalent barium ions are mainly linked by carboxylate oxygen atoms into a dimer. Neighbouring dimers are further connected by the AQTC4- ligand through carboxylate oxygen atom, leading to a 1-D chain structure. Every two adjacent chains are mainly further connected by face carboxylate oxygen atoms and water molecule, generating a two-dimensional layer structure. Such 2-D layer structures are connected with O(6) and O(6C) atoms from water molecules to form a 3-D structure. In addition, luminescent properties of 1 are also investigated. 相似文献
120.