- Development of a catalytic aromatic decarboxylation reaction
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A palladium-catalyzed aromatic decarboxylation reaction has been developed. With electron-rich aromatic adds, the reaction proceeds efficiently under fairly mild conditions in good yields. The method was useful with complex functionalized substrates containing hindered carboxylic adds.
- Dickstein, Joshua S.,Mulrooney, Carol A.,O'Brien, Erin M.,Morgan, Barbara J.,Kozlowski, Marisa C.
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Read Online
- Syntheses of benzophenone-xanthone hybrid polyketides and their antibacterial activities
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Muchimangins are benzophenone-xanthone hybrid polyketides produced by Securidaca longepedunculata. However, their biological activities have not been fully investigated, since they are minor constituents in this plant. To evaluate the possibility of muchimangins as antibacterial agent candidates, five muchimangin analogs were synthesized from 2,4,5-trimethoxydiphenyl methanol and the corresponding xanthones, by utilizing p-toluenesulfonic acid monohydrate for the Br?nsted acid-catalysis. The antibacterial assays against Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis, and Gram-negative bacteria, Klebsiella pneumoniae and Escherichia coli, revealed that the muchimangin analogs (±)-1,3,6,8-tetrahydroxy-4-(phenyl-(2′,4′,5′-trimethoxyphenyl)methyl)-xanthone (1), (±)-1,3,6-trihydroxy-4-(phenyl-(2′,4′,5′-trimethoxyphenyl)methyl)-xanthone (2), and (±)-1,3-dihydroxy-4-(phenyl-(2′,4′,5′-trimethoxyphenyl)methyl)-xanthone (3) showed significant activities against S. aureus, with MIC values of 10.0, 10.0, and 25.0?μM, respectively. Analogs (±)-1 and (±)-2 also exhibited antibacterial activities against B. subtilis, with MIC values of 50.0 and 12.5?μM, respectively. Furthermore, (+)-3 enhanced the antibacterial activity against S. aureus, with a MIC value of 10?μM.
- Kodama, Takeshi,Ito, Takuya,Dibwe, Dya Fita,Woo, So-Yeun,Morita, Hiroyuki
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Read Online
- Synthetic method of medical intermediate 1,2,4-trimethoxybenzene
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The invention discloses a synthetic method of medical intermediate 1,2,4-trimethoxybenzene. According to the synthetic method of medical intermediate 1,2,4-trimethoxybenzene, 1,2,4-triacetoxybenzene,methanol, potassium hydroxide, dimethyl sulphate, potassium carbonate, 2-aminoterephthalic acid, zirconium tetrachloride, and terephthalaldehyde are taken as main raw materials; 2-aminoterephthalic acid and zirconium tetrachloride ultrasound-assisted synthesis of a nanometer catalyst is adopted so as to realize free adsorption and desorption of reactant molecules and product molecules, realize diffusion, and at the same time achieve relatively high selectivity on products; Schiff base modification reaction with terephthalaldehyde is adopted to increase the catalytic activity of the catalyst onorganic molecule 1,2,4-trimethoxybenzene, reduce the energy barrier of the intermediate synthesis reaction system, and accelerate reaction speed. In intermediate synthesis process, the pH value of anobtained mixed solution and the dropwise adding speed of dimethyl sulphate are controlled strictly, dichloromethane is adopted for a plurality of extraction purification, so that product yield is increased greatly, production cost is reduced, production time is shortened, and excellent catalytic effect on synthesis reaction of 1,2,4-trimethoxybenzene is achieved.
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Paragraph 0008-0029
(2018/07/30)
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- A ligand-free, powerful, and practical method for methoxylation of unactivated aryl bromides by use of the CuCl/HCOOMe/MeONa/MeOH system
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A ligand-free, powerful, and practical method for mono and polymethoxylation of unactivated aryl bromides has been developed; CuCl was used as catalyst, HCOOMe as cocatalyst, and methanolic MeONa as both nucleophile and solvent. This eco-friendly procedure is characterized by operational simplicity, inexpensive substrates (unactivated mono to polybromoarenes), full conversion, and direct recovery of pure MeOH.
- Guo, Ying,Ji, Si-Zhe,Chen, Cheng,Liu, Hong-Wei,Zhao, Jian-Hong,Zheng, Yu-Lin,Ji, Ya-Fei
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p. 8651 - 8664
(2015/03/05)
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- Magnesium oxide as a heterogeneous and recyclable base for the N-methylation of indole and O-methylation of phenol using dimethyl carbonate as a green methylating agent
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This work reports a mild efficient and sustainable protocol for N-methylation of indole and O-methylation of phenol using dimethylcarbonate as an environmentally safe, non-toxic, biodegradable and green methylating agent under microwave conditions. Magnesium oxide (MgO) has been employed as a heterogeneous and recyclable base for clean N-methylation of indole and O-methylation of phenol with dimethylcarbonate. Basic properties of the fresh and recycled MgO were measured by temperature programmed desorption (CO2-TPD) analysis. The CO2-TPD runs suggested that both strong and moderately basic sites are present on the oxide, while only the moderately basic sites are responsible for the N-and O-methylation of indole and phenol, respectively, using DMC as a methylating agent. The CO2-TPD analysis showed that the basic sites on fresh and recycled MgO were comparable. The MgO was isolated by simple filtration and recycled efficiently without loss in activity and selectivity.
- Gadge, Sandip T.,Mishra, Ashish,Gajengi, Aravind L.,Shahi, Nileshkumar V.,Bhanage, Bhalchandra M.
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p. 50271 - 50276
(2014/12/10)
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- Synthesis of 2-phenylnaphthalenes from styryl-2-methoxybenzenes
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A new simple and efficient method for the synthesis of 2-phenylnaphthalenes from electron-rich 1-styryl-2-methoxybenzenes has been described. The reaction proceeds via TFA catalyzed C-C bond cleavage followed by intermolecular [4+2]-Diels-Alder cycloaddition of an in situ formed styrenyl trifluoroacetate intermediate. The quantum chemical calculations identified the transition state for the cycloaddition reaction and helped in tracing the reaction mechanism. The method has been efficiently utilized for synthesis of the phenanthrene skeleton and a naphthalene-based potent and selective ER-β agonist. This journal is
- Mudududdla, Ramesh,Sharma, Rohit,Abbat, Sheenu,Bharatam, Prasad V.,Vishwakarma, Ram A.,Bharate, Sandip B.
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supporting information
p. 12076 - 12079
(2015/02/19)
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- Mild aromatic palladium-catalyzed protodecarboxylation: Kinetic assessment of the decarboxylative palladation and the protodepalladation steps
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Mechanism studies of a mild palladium-catalyzed decarboxylation of aromatic carboxylic acids are described. In particular, reaction orders and activation parameters for the two stages of the transformation were determined. These studies guided development of a catalytic system capable of turnover. Further evidence reinforces that the second stage, protonation of the arylpalladium intermediate, is the rate-determining step of the reaction. The first step, decarboxylative palladation, is proposed to occur through an intramolecular electrophilic palladation pathway, which is supported by computational and mechanism studies. In contrast to the reverse reaction (C-H insertion), the data support an electrophilic aromatic substitution mechanism involving a stepwise intramolecular protonation sequence for the protodepalladation portion of the reaction.
- Dickstein, Joshua S.,Curto, John M.,Gutierrez, Osvaldo,Mulrooney, Carol A.,Kozlowski, Marisa C.
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p. 4744 - 4761
(2013/07/11)
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- Pd-catalyzed cross-coupling of aryl carboxylic acids with propiophenones through a combination of decarboxylation and dehydrogenation
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A palladium-catalyzed cross-coupling reaction of aryl carboxylic acids with saturated propiophenones through a combination of decarboxylation and dehydrogenation to form Heck-type products was reported. In a glove box, a 25 mL tube equipped with a stir bar was charged with Pd(OAc)2, PCy3, propiophenone, 2-nitrobenzoic acid, Ag2CO3 and nBu4NOAc HOAc. Then, the mixture was heated under nitrogen at 90°C in DMF for 24 h. After cooling down, the crude reaction mixture was analyzed by GC with n-dodecane as an internal standard to obtain 3a in 75% GC yield. Relatively weak bases, such as carboxylate salts, facilitated this reaction and the effect of the bases was a function of their solubility, while strong bases, such as K3PO4 and K2CO3 shut down the reaction completely. The simultaneous use of carboxylate salts and equimolar carboxylic acids significantly improved the yield of 3a, although the use of acetic acid alone was ineffective for the reaction.
- Zhou, Jun,Wu, Ge,Zhang, Min,Jie, Xiaoming,Su, Weiping
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supporting information; experimental part
p. 8032 - 8036
(2012/08/13)
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- Biaryl crosslinkers. I. Crosslinking of a bisazidobiaryl with poly(3-hexylthiophene)
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A new biaryl-based bisazide has been used to crosslink poly(3- hexylthiophene), a conducting polymer useful for organic electronics. Crosslinking was monitored using infrared spectroscopy and film morphology was studied using scanning electron microscopy. Hole mobility studies of the devices prepared from pristine and crosslinked polymer show an increase in hole mobility of one order of magnitude for the latter devices.
- Lohani, Jaya,Balakrishnan,Gaur, Manoj,Raghunathan,Eswaran
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p. 549 - 554
(2011/10/03)
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- Chemistry of renieramycins. Part 9: Stereocontrolled total synthesis of (±)-renieramycin G
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A 25-step stereocontrolled total synthesis of (±)-renieramycin G (1g) from readily available 2-hydroxy-3-methyl-4,5-dimethoxybenzaldehyde (3) is described. This synthesis features the concise construction of the pentacyclic framework using the stereoselective Pictet-Spengler type cyclization reaction of lactam (14) with ethyl diethoxyacetate, followed by the base-catalyzed isomerization of the C-1 stereo center.
- Yokoya, Masashi,Shinada-Fujino, Kimiko,Saito, Naoki
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body text
p. 2446 - 2449
(2011/05/16)
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- A versatile catalyst for intermolecular direct arylation of Indoles with benzoic acids as arylating reagents
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(Figure Presented) Coupled together: With a versatile catalyst system (Pd(TFA)2/Ag2CO3/propionic acid) both electron-rich and -deficient benzoic acids serve as arylating reagents for the direct functionalization of a wide rage of indoles by a combination of decarboxylation and C-H bond activation. Depending on the nature of the benzoic acids, the reaction occurs selectively at either the C2- or C3-position of indoles, which may arise from two different catalytic pathways (see scheme; TFA = trifluoroacetate).
- Zhou, Jun,Hu, Peng,Zhang, Min,Huang, Shijun,Wang, Min,Su, Weiping
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supporting information; experimental part
p. 5876 - 5881
(2010/09/05)
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- Silver-catalysed protodecarboxylation of carboxylic acids
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A silver-based catalyst system has been discovered that effectively promotes the protodecarboxylation of various carboxylic acids at temperatures of 80-120 °C - more than 50 °C below those of the best known copper catalysts. The Royal Society of Chemistry 2009.
- Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.,Fromm, Andreas
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supporting information; experimental part
p. 7173 - 7175
(2010/03/25)
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- Synthesis of 1,2,4-trimethoxybenzene and its selective functionalization at C-3 by directed metalation
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A new and efficient strategy was developed for the preparation of 1,2,4-trimethoxybenzene (3, a powerful attractant of Euglossini bees) and its C-3 derivatives (7a-j), from vanillin (2) in 56% overall yield.
- Alves, Ana P. L.,Junior, Jose Augusto B. C.,Slana, Glaucia B. A.,Cardoso, Jari N.,Wang, Qiang,Lopes, Rosangela S. C.,Lopes, Claudio C.
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experimental part
p. 3693 - 3709
(2009/12/06)
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- Design and synthesis of regioisomerically pure unsymmetrical xanthene derivatives for staining live cells and their photochemical properties
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We have demonstrated the synthesis of regioisomerically pure unsymmetrical xanthene derivatives consisting of three units which can be independently modified to control their physical properties. The photochemical properties of the synthetic unsymmetrical xanthene derivatives were investigated in solution by UV-vis absorption and fluorescence measurements, and their cell imaging properties were examined by confocal laser-scanning microscopy.
- Kamino, Shinichiro,Ichikawa, Hayato,Wada, Shun-ichi,Horio, Yuka,Usami, Yoshihide,Yamaguchi, Takako,Koda, Toshiki,Harada, Aki,Shimanuki, Kazusa,Arimoto, Masao,Doi, Mitsunobu,Fujita, Yoshikazu
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supporting information; experimental part
p. 4380 - 4384
(2009/04/06)
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- Arenium cation as the key intermediate of the electrosynthesis of N-(2,5-dimethoxyphenyl)azoles. A new approach to the synthesis of N-(dimethoxyphenyl)azoles
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Data on the effect of the acid-base properties of the medium on the yield and composition of the products of N-dimethoxyphenylation of azoles (pyrazole, triazole, their substituted derivatives, and tetrazole) upon galvanostatic electrolysis of azole-1,4-dimethoxybenzene mixtures in nucleophilic (MeOH) and neutral (MeCN) media were considered and the trends of this process were discussed. The generation of arenium cations (1,4-dimethoxy-1-azolylbenzenium in MeCN and 1,1,4-trimethoxybenzenium in MeOH) as the key intermediates of electrosynthesis of N-(dimethoxyphenyl)azoles, was proved experimentally. A new approach to the synthesis of N-(dimethoxyphenyl)azoles through electrosynthesis of 1,1,4,4-tetramethoxycyclohexa-2,5-diene by electrooxidation of 1,4-dimethoxybenzene in MeOH as the first step and the reaction of this quinone diketal with azoles as the second step was suggested. The efficiency of this route to N-(dimethoxyphenyl)azoles is comparable with the efficiency of the purely electrochemical one-step process.
- Petrosyan,Burasov
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p. 2175 - 2183
(2008/09/18)
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- Laser photolysis investigation of induced quenching in photoreduction of benzophenone by alkylbenzenes and anisoles
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The quenching processes of triplet benzophenone (JBP) by alkylbenzenes (AB) and anisole derivatives (AD) in benzene (Bz) and a mixture of acetonitriie (ACT-,) and water (4 :1 v/V; have been studied on the basis of rate constants and efficiencies determined by nanosecond laser flash photolysis a; 355 n m at 295 K. It was found that (1) the deactivation of 3BPby ADs in ACN H2O (4 :1 v/v) was governed by electron transfer (ET) to produce the benzophenone anion (BP'~) and corresponding cation (AD' + ) radicals wiih efficiencies, atj 1 whereas no chemical species were formed in Bz; and 2) photoreduction of 3BPby ABs resulted in benzophenone ketyl radical (BPK) formation by benzylic hydrogen abstraction (HA) with efficiencies XHA 1 in 3z and ACN-H2O (4 :1 v/v). The residual efficiency (a: 1 -ET or ! -aH/1) was attributed to a birnolecular process with no photochemical product, which was named 'induced-quenching (IQf. The quenching rate constants (Jcq) of ;'BPby ADs and ABs were less than the diffusion limits of both Bz and AC1~H2O (4 :1 v/v). The net bimolecular rate constants for the ET, HA and IQ processes were estimated from the k values and efficiencies. The rate constants (%T and k,Q) of ET and IQ with AD versus the oxidation potential (£) of AD followed Rchm-Weller behaviour while logarithmic rate constants {/CHA and ki(j) of HA and IQ by ABs increased linearly with a decrease in the Em of AB. It was suggested, for the deactivation mechanism of 3BPby ABs and ADs (RH), that ;1) the IQ process was intersystem crossing (ISC) enhanced by the partial charge transfer (CT) character of the triplet excipiexes, 3(BP"~- A-RHa + )a,e; (2) radical ion formation by ET might be accomplished in a polar solvent by further CT interaction in the excipiex; (3) the process of BPK formation was inferred to be H-atom transfer in the exciplex, where the more protic H-atom was readily mobile, rather than ET followed by proton transfer and (4) the loss of efficiencies of photochemicalproduct formation was derived not from back ET but from the IQ process, inherent to photoreactions, via triplet excipiexes. The deactivation processes of 3BPby RH are illustrated in Scheme 1. I ET BP'- + RH'(3BP' + RHJcoj -3(BPO- RHg,.-BPK 4 R' BP + RH Scheme 1.
- Oekada, Kafsuji,Yamaji, Minora,Smzuka, Haruo
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p. 861 - 866
(2007/10/03)
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- Electron Transfer from Aromatic Compounds to Phenyliodinium and Diphenylsulfinium Radical Cations
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Phenyliodinium (I.(+1)) and diphenylsulfinium radical cations (II.(+1)) have been generated by flash photolysis (λinc = 347 nm) of diphenyliodonium ions (I(+1)) and diphenyl(4-phenylthiophenyl)sulfonium ions (II(+1)) in acetonitrile solutions at room temperature.I.(+1) and II.(+1) were found to undergo electron-transfer reactions with benzene derivatives resulting in the formation of radical cations of the aromatic compounds.A study involving 25 compounds including various methyl- and methoxy-benzenes, biphenyl, phenol and cresols revealed that electron transfer is independent of the ionizations energy Ei provided that the rates are encounter-controlled.This applies to cases where Ei does not exceed a critical value: Ei,crit ca. 820 kJ mol-1 (I.(+1)) and 780 kJ mol-1 (II.(+1)).Bimolecular rate constants decrease with increasing Ei in the case of aromatic compounds having ionization energies exceeding the critical values.A Marcus-inverted region was not detected.
- Yagci, Y.,Schnabel, W.,Wilpert, A.,Bending, J.
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p. 287 - 292
(2007/10/02)
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- Anodic cleavage of lignin model dimers in methanol
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The anodic oxidation in methanol of some lignin model compounds, the C17-C18 compounds ((1) - (5), has been studied to ascertain factors influencing cleavage of Cα - Cβ bonds cf. substitution. Cyclic voltammetric oxidation peak potentials were influenced by structure but not by pH. Preparative-scale electrolyses gave 3,4-dimethoxybenzaldehyde as the major product from compounds (1) - (3), corresponding to cleavage of th Cα - Cβ bonds. In contrast compounds (4) and (5) were not cleaved with significant efficiency. The results are convincingly rationalised in terms of rapid cleavage of the Cα - Cβ bonds in the first-formed radical cations.
- Pardini, Vera L.,Vargas, Reinaldo R.,Viertler, Hans,Utley, James H. P.
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p. 7221 - 7228
(2007/10/02)
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- An Improved Synthesis of 1,4-Benzo- and 1,4-Naphthoquinones Bearing Active Substituents
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The synthesis of 1,4-benzoquinones and 1,4-naphthoquinones 3a-j carrying substituents such as methoxyl, allyl or oxiranyl was substantially improved.The 1-methoxy-4-methoxymethyloxy 2a-d, g-k or 1,4-bis(methoxymethyloxy) derivatives 2e-f were used, as a substrates instead of 1,4-dimethoxy derivatives 1a-j hitherto used and they were oxidized with silver(II) dipicolinate.Among numerous examples, the synthesis of a new analog of ubiquinone 3d with the oxiranyl substituent, being a new bioactivated alkylating agent, is reported.
- Syper, Ludwik,Kloc, Krystian,Mlochowski, Jacek
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p. 808 - 822
(2007/10/02)
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- Photoinduced Electron Transfer Reaction. Part 3. 9,10-Dicyanoanthracene-sensitized Photo-oxidation of Electron-rich Stilbene Oxides
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The 9,10-dicyanoanthracene (DCA)-sentisized photo-oxygenation of the electron-rich stilbene oxides (1) gives the ozonides (2) almost quantitatively.The fluorescence of DCA is quenched by (1) at a diffusion-controlled rate and the above reaction is quenched by polymethoxybenzenes which indicates that an electron transfer mechanism is involved.The quantum yield for ozonide formation varies from 0.6 for trans-2-(4-methoxyphenyl)-3-phenyloxirane (1d) to 2.4 for trans-2,3-bis(4-methoxyphenyl)-2,3-diethyloxirane (1h), suggesting a duplex reaction mechanism such as photo-oxygenation by superoxide and a Barton mechanism after the initial electron transfer from the epoxides (1) to the excited singlet state of DCA.
- Futamura, Shigeru,Kusunose, Shosaku,Ohta, Hiroyuki,Kamiya, Yoshio
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- ORTHO-HYDROXYLATION SELECTIVE DES PHENOLS : II - UN NOUVEAU SYSTEME CATALYTIQUE A CARACTERE PREPARATIF.
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A direct synthetic transformation of phenols into copper(II) catecholates (i.e. catechols) is described, which involves a copper-catalyzed activation of molecular oxygen.The mechanism and scope of this new reaction are discussed.
- Capdevielle, Patrice,Maumy, Michel
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p. 1577 - 1580
(2007/10/02)
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- SELECTIVE DEALKYLATIONS OF ARYL ALKYL ETHERS AND THIOETHERS BY SODIUM IN HMPA
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The reaction of sodium with bis- and tris(alkoxy)benzenes in HMPA gives selectively the products of monodealkylation.The reaction proceeds through a dianion which fragments into an alkyl and an aryloxy anion.The positional selectivity of this fragmentation is governed by the structure of both the alkyl and aryloxy groups.With bis- and tris(alkoxy)benzenes which for symmetry reasons can afford aryloxy anions having the same basicity, the dealkylation involves exlusively the less substituted alkyl group.On the contrary, in the asymmetric terms, the positional selectivity of the dealkylation process is governed by the basicity of the aryloxy anion.On the basis of these concepts several efficient and synthetically useful reactions have been developed.In most cases the selectivity obtained in the present reactions in different from that observed with other previously developed methods which use sodium methoxide or sodium alkenethiolates in HMPA.It is shown that the appropriate choice of the reagent allows selective dealkylation of the desired alkoxy group of a poly(alkoxy)benzene.The reaction of sodium with bis(alkylthio)benzenes in HMPA gives the bis(mercapto)benzenes.If the reduction is carried out with a solution of sodium in HMPA, the reaction gives instead the products of monodealkylation.This however is not selective.It is suggested that in the case of thioethers the dealkylation products originate from the fragmentation of the radical anions.
- Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
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p. 3687 - 3692
(2007/10/02)
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