- Kinetics of the hydride reduction of an NAD+ analogue by isopropyl alcohol in aqueous and acetonitrile solutions: Solvent effects, deuterium isotope effects, and mechanism
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(Chemical Equation Presented) The rate constants of the hydride-transfer reactions from isopropyl alcohol (i-PrOH) to an NAD+ model, 9-phenylxanthyliumion (PhXn+), in acetonitrile (AN) and inwater containing AN (80% H2O/20% AN) were determined over a temperature range from 36 to 67°C. The reactions follow second-order rate laws. In the latter solution, formation of the water adduct of PhXn+ was observed as a side-equilibrium (K). The observed inverse solvent kinetic isotope effect (kH2Oobs/kD2Oobs = 0.54), the larger than unity equilibrium isotope effect (K(H2O)/K(D2O) = 2.69), and the results of acid effect on the observed rate constants of the reactions are consistent with the "side-equilibriummechanism". Kinetic isotope effects at all three H/D positions of i-PrOH for the net hydride-transfer process were determined in both solutions at 60°C: KIE α-DH = 3.2(AN), 3.2(H2O); KIE β-D6H = 1.05(AN), 1.16(H2O); KIE ODH = 1.08(AN), 1.04(H2O). These KIE values are consistent with the presence of the positively charged alcohol moiety in the transition state (TS) for cleavage of the α-C-H bond, the delocalization of the positive charge over the α-C-OH group, and the stepwise hydride and proton transfer processes. Comparison of the activation parameters for the reactions in the two solvent systems as well as those in the i-PrOH/AN (1:1 v/v) reported earlier suggests that the AN medium promotes the reaction by activating the ground-state alcohol reactant through weak interactions with the electron pairs on alcohol O, while water and parent alcohol media facilitate the reaction by H-bonding stabilization of the alcohol moiety of the TS. Results suggest that in the alcohol dehydrogenases without a Zn(II) cofactor in the active sites alcohols would be oxidized via hydride transfer to NAD+ coenzyme followed by the rapid deprotonation to the nearby basic species in the active site of the enzymes.
- Lu, Yun,Qu, Fengrui,Zhao, Yu,Small, Ashia M. J.,Bradshaw, Joshua,Moore, Brian
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Read Online
- Deoxygenation of tertiary and secondary alcohols with sodium borohydride, trimethylsilyl chloride, and potassium iodide in acetonitrile
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The deoxygenation of tertiary and secondary alcohols to give the corresponding alkanes is conventionally performed using an organosilane and a strong acid. In this study, a deoxygenation method was developed for tertiary and secondary alcohols, using trimethylsilane and trimethylsilyl iodide generated in situ from sodium borohydride and trimethylsilyl chloride, and trimethylsilyl chloride and potassium iodide, respectively. With our method, tertiary and secondary alcohols, which provided stable carbocations, were converted into the corresponding alkanes. This paper also presents the optimization of the reaction conditions, the reaction mechanism, as well as the scope and limitations of the method.
- Kato, Yuichi,Inoue, Tomoka,Furuyama, Yuuki,Ohgane, Kenji,Sadaie, Mahito,Kuramochi, Kouji
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supporting information
(2021/11/16)
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- NaHSO4/SiO2catalyzed generation of: o -quinone/ o -thioquinone methides: synthesis of arylxanthenes/ arylthioxanthenes via oxa-6π-electrocyclization
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ortho-Quinone methides, very reactive transient intermediates, are utilized successfully in synthesizing complex organic molecules of natural and biological significance. Among several synthetic protocols, the acid catalyzed generation of ortho-quinone me
- Anthony, Savarimuthu Philip,Karthick, Muthupandi,Konikkara Abi, Edwin,Ramanathan, Chinnasamy Ramaraj,Someshwar, Nagamalla
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p. 8653 - 8667
(2020/11/17)
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- Asymmetric carbazole pyridine compound and applications thereof
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The invention belongs to the field of organic electroluminescent materials, and discloses an asymmetric carbazole pyridine compound and applications thereof. The provided compound has a structure represented by the formula (I) and a high triplet energy le
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Paragraph 0159; 0161; 0162
(2019/05/08)
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- Method for constructing carbon-hydrogen bond by catalyzing alcohol dehydroxylation with palladium/platinum
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The invention discloses a method for constructing a carbon-hydrogen (deuterium) bond. The method comprises the following step: in the presence of a palladium/platinum catalyst and aryl halide, an alcohol hydroxyl group of an alcohol and hydrogen (deuterium) gas is replaced by hydrogen (deuterium) to construct the carbon-hydrogen (deuterium) bond. According to the method, the palladium/platinum catalyst is used as a catalyst, the green hydrogen (deuterium) gas is used as a hydrogen (deuterium) source, efficient alcohol dehydroxylation is performed at room temperature to construct the carbon-hydrogen (deuterium) bond, and the method is particularly suitable for constructing the carbon-deuterium bond and can be widely applied to synthesis of deuterated drugs.
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Paragraph 0104-0110; 0112
(2019/12/25)
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- Copper-Catalyzed One-Pot Synthesis of Dibenzofurans, Xanthenes, and Xanthones from Cyclic Diphenyl Iodoniums
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Oxygenation of cyclic diphenyl iodoniums (CDPIs) with varied medium-ring sizes has been fully investigated. This practical copper-catalyzed tandem reaction of CDPIs with water as the oxygen source enables the construction of derivatised dibenzofurans and xanthenes at moderate to good yields. Moreover, structurally important xanthones are also successfully accessed under the oxygenation conditions with additional TEMPO.
- Zhu, Daqian,Li, Min,Wu, Zhouming,Du, Yongliang,Luo, Bingling,Huang, Peng,Wen, Shijun
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p. 4566 - 4571
(2019/07/09)
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- Elemental steps of the thermodynamics of dihydropyrimidine: a new class of organic hydride donors
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25 Dihydropyrimidine derivatives, a new class of organo-hydrides, were designed and synthesized by the Biginelli reaction. For the first time, the thermodynamic driving forces of the six elemental steps to obtain a hydride in acetonitrile were determined by isothermal titration and electrochemical methods, respectively. The effects of molecular structures and substituents on these thermodynamic parameters were examined, uncovering some interesting structure-reactivity relationships. Both the thermodynamic and kinetic studies show that the hydride transfer from dihydropyrimidines to 9-phenylxanthylium (PhXn+ClO4-) prefers a concerted mechanism.
- Meng, Fan-kun,Zhu, Xiao-qing
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p. 197 - 206
(2016/12/27)
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- Efficient C(sp3)-H bond functionalization of isochroman by azadol catalysis
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A novel organocatalytic C(sp3)-H bond functionalization of isochroman under practical conditions has been developed. In the presence of 5.0 mol % of AZADOL, the catalysis proceeded successfully with a broad range of substrates and nucleophiles in excellent yields.
- Muramatsu, Wataru,Nakano, Kimihiro
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p. 1549 - 1552
(2015/03/30)
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- LDA-Mediated Synthesis of Triarylmethanes by Arylation of Diarylmethanes with Fluoroarenes at Room Temperature
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A practical and convenient approach for the secondary C(sp3)-H arylation of diarylmethanes with various fluoroarenes is described. The reaction proceeds smoothly in the presence of LDA (lithium diisopropylamide) at room temperature and affords triarylmethanes in moderate to high yields.
- Ji, Xinfei,Huang, Tao,Wu, Wei,Liang, Fang,Cao, Song
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supporting information
p. 5096 - 5099
(2015/11/03)
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- NiXantphos: A deprotonatable ligand for room-temperature palladium-catalyzed cross-couplings of aryl chlorides
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Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd-NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp2)-H arylations. The advantages and importance of the Pd-NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides.
- Zhang, Jiadi,Bellomo, Ana,Trongsiriwat, Nisalak,Jia, Tiezheng,Carroll, Patrick J.,Dreher, Spencer D.,Tudge, Matthew T.,Yin, Haolin,Robinson, Jerome R.,Schelter, Eric J.,Walsh, Patrick J.
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supporting information
p. 6276 - 6287
(2014/05/20)
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- Unusual Reaction Constant for Hydride Transfer from a Carbanion to 9-Arylxanthyliums
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The reaction constant (ρ) from the kinetics for hydride transfer from a carbanion (XH-) to 9-arylxanthylium ions (9-GPhXn+) in CH3CN was unusually negative. Thermodynamic analysis indicated that ρ for the simple hydride tr
- Liu, Fengrui,Zhu, Xiaoqing
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supporting information
p. 7329 - 7332
(2016/02/18)
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- A classical but new kinetic equation for hydride transfer reactions
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A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions. The Royal Society of Chemistry.
- Zhu, Xiao-Qing,Deng, Fei-Huang,Yang, Jin-Dong,Li, Xiu-Tao,Chen, Qiang,Lei, Nan-Ping,Meng, Fan-Kun,Zhao, Xiao-Peng,Han, Su-Hui,Hao, Er-Jun,Mu, Yuan-Yuan
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p. 6071 - 6089
(2013/09/12)
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- Imbalanced tunneling ready states in alcohol dehydrogenase model reactions: Rehybridization lags behind H-tunneling
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The secondary kinetic isotope effects for the hydride transfer reactions from aliphatic alcohols to two carbocations (NAD+ models) in acetonitrile were determined. The results suggest that the hydride transfer takes place by tunneling and that the rehybridizations of both donor and acceptor carbons lag behind the H-tunneling. This is quite contrary to the observations in alcohol dehydrogenases where the importance of enzyme motions in catalysis is manifested.
- Hammann, Blake,Razzaghi, Mortezaali,Kashefolgheta, Sadra,Lu, Yun
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supporting information
p. 11337 - 11339
(2013/01/15)
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- Ion pair pKs of some amines: Extension of the computed lithium pK scale
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The pK of p-(methylamino)biphenyl, 1, on our Li scale, pK(Li) = 22.09, compared to the cesium scale, pK(Cs) = 28.60. For hexamethyldisilazane, HMDS, pK(Li) = 23.05, pK(Cs) = 29.26. These results are those for the monomers in THF; corrections were made for dimers present in some cases. The pK(Li) of these two amines fit well the previously found correlation with Hartree-Fock calculations at 6-31+g(d) using RLi coordinated with three dimethyl ethers as a computational model for RLi in THF. The results are also compared with earlier pK(Li)s reported from equilibria with lithium amides in which aggregation was not considered.
- Streitwieser, Andrew,Facchetti, Antonio,Xie, Linfeng,Zhang, Xingyue,Wu, Eric C.
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supporting information; scheme or table
p. 985 - 990
(2012/03/26)
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- Structure-reactivity relationship for alcohol oxidations via hydride transfer to a carbocationic oxidizing agent
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Second-order rate constants were determined for the oxidation of 27 alcohols (R1R2CHOH) by a carbocationic oxidizing agent, 9-phenylxanthylium ion, in acetontrile at 60°C. Alcohols include open-chain alkyl, cycloalkyl, and unsaturated alcohols. Kinetic isotope effects for the reaction of 1-phenylethanol were determined at three H/D positions of the alcohol (KIEα-D=3.9, KIEβ-D3=1.03, KIE OD=1.10). These KIE results are consistent with those we previously reported for the 2-propanol reaction, suggesting that these reactions follow a hydride-proton sequential transfer mechanism that involves a rate-limiting formation of the α-hydroxy carbocation intermediate. Structure-reactivity relationship for alcohol oxidations was deeply discussed on the basis of the observed structural effects on the formation of the carbocationic transition state (Cδ+-OH). Efficiencies of alcohol oxidations are largely dependent upon the alcohol structures. Steric hindrance effect and ring strain relief effect win over the electronic effect in determining the rates of the oxidations of open-chain alkyl and cycloalkyl alcohols. Unhindered secondary alkyl alcohols would be selectively oxidized in the presence of primary and hindered secondary alkyl alcohols. Strained C7-C11 cycloalkyl alcohols react faster than cyclohexyl alcohol, whereas the strained C5 and C12 alcohols react slower. Aromatic alcohols would be efficiently and selectively oxidized in the presence of aliphatic alcohols of comparable steric requirements. This structure-reactivity relationship for alcohol oxidations via hydride-transfer mechanism is hoped to provide a useful guidance for the selective oxidation of certain alcohol functional groups in organic synthesis. Copyright
- Lu, Yun,Bradshaw, Joshua,Zhao, Yu,Kuester, William,Kabotso, Daniel
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p. 1172 - 1178
(2013/01/12)
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- What are the differences between ascorbic acid and NADH as hydride and electron sources in vivo on thermodynamics, kinetics, and mechanism?
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Ascorbic acid (AscH2) and dihydronicotinamide adenine dinucleotide (NADH) are two very important natural redox cofactors, which can be used as hydride, electron, and hydrogen atom sources to take part in many important bioreduction processes in vivo. The differences of the two natural reducing agents as hydride, hydrogen atom, and electron donors in thermodynamics, kinetics, and mechanisms were examined by using 5,6-isopropylidene ascorbate (iAscH-) and β-d-glucopyranosyl-1, 4-dihydronicotinamide acetate (GluNAH) as their models, respectively. The results show that the hydride-donating ability of iAscH- is smaller than that of GluNAH by 6.0 kcal/mol, but the electron-donating ability and hydrogen-donating ability of iAscH- are larger than those of GluNAH by 20.8 and 8.4 kcal/mol, respectively, which indicates that iAscH- is a good electron donor and a good hydrogen atom donor, but GluNAH is a good hydride donor. The kinetic intrinsic barrier energy of iAscH- to release hydride anion in acetonitrile is larger than that of GluNAH to release hydride anion in acetonitrile by 6.9 kcal/mol. The mechanisms of hydride transfer from iAscH- and GluNAH to phenylxanthium perchlorate (PhXn+), a well-known hydride acceptor, were examined, and the results show that hydride transfer from GluNAH adopted a one-step mechanism, but the hydride transfer from iAscH- adopted a two-step mechanism (e-H?). The thermodynamic relation charts (TRC) of the iAscH- family (including iAscH-, iAscH?, iAsc?-, and iAsc) and of the GluNAH family (including GluNAH, GluNAH?+, GluNA?, and GluNA+) in acetonitrile were constructed as Molecule ID Cards of iAscH- and of GluNAH in acetonitrile. By using the Molecule ID Cards of iAscH- and GluNAH, the character chemical properties not only of iAscH- and GluNAH but also of the various reaction intermediates of iAscH- and GluNAH all have been quantitatively diagnosed and compared. It is clear that these comparisons of the thermodynamics, kinetics, and mechanisms between iAscH- and GluNAH as hydride and electron donors in acetonitrile should be quite important and valuable to diagnose and understand the different roles and functions of ascorbic acid and NADH as hydride, hydrogen atom, and electron sources in vivo.
- Zhu, Xiao-Qing,Mu, Yuan-Yuan,Li, Xiu-Tao
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scheme or table
p. 14794 - 14811
(2012/03/13)
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- Hydride, hydrogen, proton, and electron affinities of imines and their reaction intermediates in acetonitrile and construction of thermodynamic characteristic graphs (TCGs) of imines as a molecule ID card
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(Chemical Equation Presented) A series of 61 imines with various typical structures were synthesized, and the thermodynamic affinities (defined as enthalpy changes or redox potentials in this work) of the imines to abstract hydride anions, hydrogen atoms, and electrons, the thermodynamic affinities of the radical anions of the imines to abstract hydrogen atoms and protons, and the thermodynamic affinities of the hydrogen adducts of the imines to abstract electrons in acetonitrile were determined by using titration calorimetry and electrochemical methods. The pure heterolytic and homolytic dissociation energies of the C=N π-bond in the imines were estimated. The polarity of the C=N double bond in the imines was examined using a linear free-energy relationship. The idea of a thermodynamic characteristic graph (TCG) of imines as an efficient Molecule ID Card was introduced. The TCG can be used to quantitatively diagnose and predict the characteristic chemical properties of imines and their various reaction intermediates as well as the reduction mechanism of the imines. The information disclosed in this work could not only supply a gap of thermodynamics for the chemistry of imines but also strongly promote the fast development of the applications of imines. 2009 American Chemical Society.
- Zhu, Xiao-Qing,Liu, Qiao-Yun,Chen, Qiang,Mei, Lian-Rui
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scheme or table
p. 789 - 808
(2010/04/29)
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- A new synthetic route to unsymmetrical 9-arylxanthenes
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A. facile and general three-step synthetic route towards unsymmetrical 9-arylxanthenes was developed. The reaction sequence involves nucleophilic substitution of commercially available 2-fluorobenzaldehydes with arenoxides, Grignard reaction of the resulting 2-arenoxybenzaldehydes with arylmagnesium bromides, followed by FeCl3-catalyzed intramolecular diarylmethylation of the resulting carbinols, This strategy was extended to access symmetrical as well as unsymmetrical 9-arylthioxanthenes.
- Das, Sajal Kumar,Singh, Ritesh,Panda, Gautam
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scheme or table
p. 4757 - 4761
(2010/02/28)
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- Hydride reduction of NAD+ analogues by isopropyl alcohol: kinetics, deuterium isotope effects and mechanism
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(Chemical Equation Presented) Observed pseudo-first-order rate constants (kobs) of the hydride-transfer reactions from isopropyl alcohol (i-PrOH) to two NAD+ analogues, 9-phenylxanthylium ion (PhXn +) and 10-methylacridini
- Lu, Yun,Qu, Fengrui,Moore, Brian,Endicott, Donald,Kuester, William
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p. 4763 - 4770
(2008/12/21)
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- Hydride affinities of cumulated, isolated, and conjugated dienes in acetonitrile
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(Chemical Equation Presented) The hydride affinities (defined as the enthalpy changes in this work) of 15 polarized dienes [five phenyl sulfone substituted allenes (1a), the corresponding five isolated dienes (1b), and the corresponding five conjugated dienes (1c)] in acetonitrile solution were determined by titration calorimetry for the first time. The results display that the hydride affinity scales of the 15 dienes in acetonitrile range from -71.6 to -73.9 kcal/mol for 1a, from -46.2 to -49.7 kcal/mol for 1b, and from -45.0 to -46.5 kcal/mol for 1c, which indicates that the hydride-obtaining abilities of the cumulated dienes (1a) are not only much larger than those of the corresponding conjugated dienes (1c) but also much larger than those of the corresponding isolated dienes (1b). The hydrogen affinities of the 15 dienes as well as the hydrogen affinities and the proton affinities of the radical anions of the dienes (1-.) in acetonitrile were also evaluated by using relative thermodynamic cycles according to Hess's law. The results show that (i) the hydrogen affinities of the neutral dienes 1 cover a range from -44.5 to -45.6 kcal/mol for 1a, from -20.4 to -21.4 kcal/ mol for 1b, and from -17.3 to -18.5 kcal/mol for 1c; (ii) the hydrogen affinities of the radical anions of the dienes (1-.) in acetonitrile cover a range from -40.6 to -47.2 kcal/mol for 1a-., from -21.6 to -29.6 kcal/mol for 1b-., and from -10.0 to -15.4 kcal/mol for 1c-.; (iii) the proton affinities of the 15 1a-. in acetonitrile cover a range from -97.0 to -100.6 kcal/mol for 1a-., from -77.8 to -83.4 kcal/ mol for 1b -., and from -66.2 to -68.9 kcal/mol for 1c-.. The main reasons for the great difference between the cumulated dienes and the corresponding isolated and conjugated dienes in the hydride affinity, hydrogen affinity, and proton affinity have been examined. It is evident that these experimental results should be quite valuable to facilitate the elucidation of the origins of the especially high chemical potencies of the allenes, the choice of suitable hydride reducing agents to reduce the dienes, and the analyses on the reduction mechanisms.
- Zhu, Xiao-Qing,Liang, Hao,Zhu, Yan,Cheng, Jin-Pei
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scheme or table
p. 8403 - 8410
(2009/04/11)
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- A 2:1 coupling reaction of arynes with aldehydes via o-quinone methides: Straightforward synthesis of 9-arylxanthenes
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(Chemical Equation Presented) A novel coupling reaction, where an aldehyde and two molar amounts of an aryne are assembled selectively, has been demonstrated to afford diverse 9-arylxanthene derivatives in one step. o-Quinone methide arising from the [2 + 2] cycloaddition of an aldehyde with an aryne was postulated as a transient intermediate.
- Yoshida, Hiroto,Watanabe, Masahiko,Fukushima, Hiroyuki,Ohshita, Joji,Kunai, Atsutaka
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p. 4049 - 4051
(2007/10/03)
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- Acidity of dibasic carbon acids. Part 5.1-4 the second acidity constant of 9,10-dihydrodibenz[a,h]anthracene in tetrahydrofuran - Geometry, charge distribution of dianion, structure of dimetallic salts
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The second equilibrium ion pair acidity constant (pK2) of 9,10-dihydrodibenz[a,h]anthracene (DBDHA, 1H2) with counter ions sodium (pK2 28.5) and potassium (pK2 30.4) has been determined in tetrahydrofuran (THF)
- Nir, Malka,Shapiro, Israel O.,Rabinovitz, Mordecai
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p. 329 - 332
(2007/10/03)
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- Equilibrium acidities of some sulfones and sulfoxides in tetrahydrofuran
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Ion pair acidities are reported in tetrahydrofuran (THF) solution for the lithium and cesium salts of several sulfones and one sulfoxide. These salts are shown to be monomeric in the THF solutions studied. Thermodynamic constants are reported for several salts. The results and some conductivity studies show that both the lithium and cesium salts are contact ion pairs in THF. Because of ion association the relative pKs are slightly lower for cesium salts and much lower for lithium salts than for the free ions in DMSO solution.
- Streitwieser, Andrew,Wang, George Peng,Bors, Daniel A.
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p. 10103 - 10112
(2007/10/03)
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- Intrazeolite photochemistry. 12. Ship-in-a-bottle synthesis and control of the photophysical properties of 9-(4-methoxyphenyl)xanthenium ion imprisoned into large-pore zeolites
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The 9-(4-methoxyphenyl)xanthylium ion (AnX+), a bulky cation that according to molecular modeling simulations cannot enter through the 7.4 A pore opening of tridirectional large-pore zeolites Y and β, has been prepared by ship-in-a-bottle synthesis within the supercages of these two zeolites. The synthetic procedure involves two steps: (i) generation of xanthylium cation (X+) adsorbed within the zeolite by treatment of xanthydrol onto the H+ form of these solids; (ii) electrophilic attack of the cation to anisole within the framework of the zeolite. Carrying out the same procedure using toluene or benzene or using an alternative process involving the reaction of xanthone with anisole, led to the corresponding 9-arylxanthylium ions together with some unidentified adventitious material. Textural and acidic properties of these composites were tested using α-methylstyrene dimerization and were found to be very similar to the original HY or Hβ zeolites, thus indicating an internal location for AnX+. Entrapment within the zeolite framework restricts AnX+ conformational mobility, thwarting the deactivation pathway occurring in solution. This has allowed for the first time characterization of its triplet excited state as a long-lived transient species (tens of microseconds), as well as the observation of room-temperature fluorescence in the nanosecond range.
- Cano, Maria Luz,Cozens, Frances L.,Fornes, Vicente,Garcia, Hermenegildo,Scaiano
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p. 18145 - 18151
(2007/10/03)
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- STABILITIES OF SOME 2-(PARA-SUBSTITUTED-PHENYL)-4,4,5,5-TETRAMETHYL-1,3-DIOXOLANES RELATIVE TO THEIR CONJUGATE DIOXOLENIUM IONS, RADICALS AND CARBANIONS AS DETERMINED BY THERMODYNAMICS FOR HYDRIDE AND ELECTRON TRANSFER IN SOLUTION
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A calorimetric method is described for the determination of the hydride affinities, ΔHH-(R+) of seven dioxolenium ions from the title compounds and also tropylium, trityl and 9-phenylxanthylium cations by hydride transfer to the carb
- Arnett, Edward M.,Flowers, Robert A.,Meekhof, Alison E.,Pourjavadi, Ali,Walek, Stuart A.
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p. 663 - 671
(2007/10/02)
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- Thermal and Photochemical Decomposition of 9-Arylxanthen-9-yl Hydroperoxides and Peroxides
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The thermolysis and photolysis of a series of 9-arylxanthenyl hydroperoxides and peroxides have been investigated by means of differential scanning calorimetry, electron paramagnetic spectroscopy and product studies.These relatively stable peroxidic compounds were found to rearrange smoothly on being heated at temperatures > 120 deg C and on photolysis, respectively, through concerted reaction pathways.Photolysis of 9-hydroperoxy-9-phenylxanthene and di(9-phenylxanthen-9-yl)peroxide, respectively, have been shown by EPR spectroscopy to generate 9-phenylxanthenyl radicals which dimerise at low temperatures and reform the free radicals at ambient temperature.
- Goosen, Andre,McCleland, Cedric W.,Taljaard, Benjamin
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p. 995 - 1000
(2007/10/02)
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- Carbon Acidity. 79. Acidity of Enolate Equivalent Compounds: Oxime Ethers
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A series of benzylic oxime ethers were synthesized (CH3ON=C(CH2Ar)2, Ar = phenyl (1), 4-biphenylyl (2), 1-naphthyl (3), and the equilibrium ion pair acidities in THF were determined.The lithium ion pair acidity of 1 was found to be approximately 5 pK units lower than the corresponding cesium ion pair acidity.The oxime ethers are approximately 10 orders of magnitude less acidic than their corresponding ketones for cesium ion pairs.Thermodynamic parameters for the equilibrium acidities were measured and are consistent for contact ion pair monomers being the important species in solution.An aggregation study also indicated that these cesium oxime ether enolates exist mainly as ion pair monomers.The role of gegenion in the stability of oxime ether anions is discussed.
- Ciula, James C.,Streitwieser, Andrew
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p. 1989 - 1993
(2007/10/02)
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- Conversion of aromatic ketones, benzyl alcohols, and alkyl aryl ethers to aromatic hydrocarbons with lithium 4,4'-di-t-butylbiphenyl radical anion
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Treatment of tetrahydrofuran (THF) solutions of the title compounds with excess lithium (or potassium) metal under ultrasonic irradiation in the presence of catalytic amounts of the electron-transfer agent 4,4'-di-t-butylbiphenyl (DBB) caused conversions to aromatic hydrocarbons in good yields. Addition of 1 or 2 equiv of alkyl halides prior to aq ammonium chloride treatment during workup provided mono- or di-alkylated products.
- Karaman,Kohlman,Fry
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p. 6155 - 6158
(2007/10/02)
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- CRYPTATE ACIDITY SCALES. V. EQUILIBRIUM ACIDITY OF INDICATOR CH-ACIDS IN TETRAHYDROFURAN
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A scale of equilibrium cryptate acidity in tetrahydrofuran is constructed.Its distinguishing feature is the constancy of the contribution from ionic association.A method is proposed for determination of the constants for the association of the ions into ion pairs in dimethyl sulfoxide.
- Antipin, I. S.,Gareev, R. F.,Vedernikov, A. N.,Konovalov, A. I.
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p. 1039 - 1044
(2007/10/02)
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- CRYPTATE ACIDITY SCALES. VI. EFFECT OF POLARITY OF THE MEDIUM ON CRYPTATE ION-PAIR ACIDITY
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A thermodynamic analysis was made of the effects of various types of solvation interactions on ion-pair acidity.It was shown that the polarity of the medium does not have an effect on the relative cryptate acidity of organic compounds.
- Antipin, I. S.,Vedernikov, A. N.,Solomonov, B. N.,Konovalov, A. I.
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p. 1861 - 1865
(2007/10/02)
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- REACTIVITIES OF HETEROAROMATIC CATIONS CONTAINING A GROUP VIB ELEMENT IN NUCLEOPHILIC REACTIONS. REACTIONS OF 9-PHENYL-XANTHYLIUM, -THIOXANTHYLLIUM, AND -SELENOXANTHYLIUM SALTS WITH AMINES, SODIUM PHENOLATE, AND SODIUM BENZENETHIOLATE
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Reactions of 9-phenylchalcogenoxanthyllium salts (1a-c) with some nucleophiles have been examined in order to find the differences in reactivity in nucleophilic reactions.The chalcogenoxanthylium salts (1a-c) react with aniline in ether to give 9-anilino-9-phenylchalcogenoxanthenes (7a-c).However, in acetonitrile the xanthylium salt (1a) affords N,4-bis(9-phenylxanthen-9-yl)aniline (9a) together with the anilinoxanthene (7a) (at room temperature) or 9-(p-aminophenyl)-9-phenylxanthene (8a) (at reflux) and the sulphur (1b) and the selenium derivative (1c) affords only the anilino derivatives (7b,c), respectively.In the reactions with sodium phenolate, the thioxanthylium salt (1b) gave 9-phenoxy-9-phenylthioxanthene (13b), whereas the oxygen (1a) and the selenium congener (1c) gave O,4-bis(9-phenylchalcogenoxanthen-9-yl)phenols (15a,c) together with the 9-phenoxy derivatives (13a,c), respectively.The results show that the thioxanthylium salt (1b) gave the products formed on attack by the heteroatom of the ambident nucleophiles and the ratio of the carbon attack increased in the order (1a) > (1c) > (1b).This difference would be attributable to the properties of carbocations at the 9-position in the heteroaromatic cations (1a-c).
- Hori, Mikio,Kataoka, Tadashi,Shimizu, Hiroshi,Hsu, Chen Fu,Hasegawa, Yukio,Eyama, Noriko
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p. 2271 - 2276
(2007/10/02)
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- Aspects of the Chemistry of Donor Solvent Coal Dissolution Reactions. The Reduction of Benzophenone and the Diproportionation of Benzhydrol in Hydrocarbon Solvents at High Temperature
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The reduction of benzophenone by hydrogen donor molecules such as tetralin and dihydroanthracene to give diphenylmethane was investigated in the temperature range 300-400 deg C.Several lines of evidence indicate that the reaction occurs in three distinct stages.The first stage is a radical process which gives benzhydrol.In the second stage, this intermediate undergoes an SN reaction to produce water and bis(diphenylmethyl) ether.The ether disproportionates in a readily initiated, free radical chain reaction to give diphenylmethane and benzophenone.
- Choi, Chol-yoo,Stock, Leon M.
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p. 2871 - 2875
(2007/10/02)
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- Molecular rearrangements. Part XX. Thermolysis of carboxylic acid esters
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Thermolysis of phenyl benzoate on heating under reflux for ca. 10 days in a nitrogen atmosphere gives phenol, o- and p-hydroxybiphenyl, biphenyl, and carbon monoxide.Phenyl phenylacetate under the same conditions gives toluene, bibenzyl, stilbene, phenol, o- and p-benzylphenol, 9-phenylxanthene, water, and carbon monoxide.Thermolysis of benzyl benzoate is accompanied by decarboxylation and the formation of toluene, diphenylmethane, bibenzyl, stilbene, and biphenyl.Thermolysis of benzyl phenylacetate proceeds smoothly, affording carbon dioxide, toluene, bibenzyl, and stilbene.It was concluded that thermolysis of esters proceeds through a free radical mechanism involving homolytic fission of either the O-CO or O-alkyl bond with subsequent decomposition of the radicals so formed.
- Aly, M. M.,Badr, M. Z. A.,Fahmy, A. M.,Mahgoub, S. A.
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p. 1532 - 1535
(2007/10/02)
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- ACIDIFYING EFFECTS OF AZA GROUPS IN THE NH ACIDITY OF AMINOAZINES AND THE CH ACIDITY OF ACETYLAZINES
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The pK values for a series of aminoazines and acetylazines containing one, two, or three aza groups in the ring were determined in dimethyl sulfoxide.There is a good linear correlation between pK values of the investigated NH and CH acids.The acidifying effects (ΔpK) of the aza groups at positions 2, 3, or 4 in relation to the side chain were determined and had values of 3.1, 2.4, and 4.5 logarithmic units in the aminoazines and 3.5, 2.9 and 4.8 logarithmic units respectively in the acetylazines.Except in the case of two ortho-located aza groups the effects are additive.Compared with dimethyl sulfoxide water has a differentiating effect on the acidity of the aminoazines, and this is explained by the formation of hydrogen bonds between the molecules of the proton-donating solvent and the aza groups of the anions of the aminoazines.
- Terekhova, M. I.,Petrov, E. S.,Mikhaleva, M. A.,Shkurko, O. P.,Mamaev, V. P.,Shatenshtein, A. I.
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- Solid-State Dehydration of (o-Hydroxyaryl)diphenylmethanols. Crystal and Molecular Structures of diphenylmethanol and of diphenylmethanol
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The rearrangement of diphenylmethanol (3) to the corresponding fuchsone (4) has been shown to proceed in the solid state (either as a reaction of powders or syngle crystals)when induced thermally or photothermally.The thermal reactio
- Lewis, Terry W.,Duesler, Eileen N.,Kress, Ruth B.,Curtin, David Y.,Paul, Iain C.
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p. 4659 - 4664
(2007/10/02)
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