- Single Electron Transfer Reactions of the Ambident Anion of 2-Cyano-3-ethyl-1-methyl-Δ3-piperideine
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The reaction of the ambident anion (2) derived from 2-cyano-3-ethyl-1-methyl-Δ3-piperideine (1) with t-butyl halides and p-NO2C6H4CH2X led to formation of the C-2 product (3) and the C-4 product (6) respectively via a probable single electron transfer reaction; dimerization of anion (2) gave dimers (8), (9), and (10) by electron transfer to m-dinitrobenzene, I2, and 2-methyl-2-nitropropane.
- Grierson, David,Urrea, Miguel,Husson, Henri-Phillippe
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- Deoxygenation of Ethers to Form Carbon-Carbon Bonds via Nickel Catalysis
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In this article a successful protocol was developed to construct carbon-carbon bonds by the extrusion of the O atom of ethers via nickel catalysis in the presence of reductants. This methodology is featured as a highly economic route to construct sp3-sp3 C-C bonds through dual C-O activation of ethers with good functional group tolerance.
- Cao, Zhi-Chao,Shi, Zhang-Jie
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- Picosecond and Nanosecond Laser Photolyses of p-Nitrophenylacetate in Aqueous Media. A Photoadiabatic Decarboxylation Process?
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Employing UV picosecond (266 nm, 22 ps, ca. 0.5 mJ) and nanosecond (266 nm, 12 ns, 0.5-5 mJ) excitation, we have investigated the dynamics of the photodecarboxylation of p-nitrophenylacetate anions in aqueous solution.In agreement with previous micosecond flash photolysis studies, we believe that the primary decarboxylation products are the p-nitrobenzyl anion and carbon dioxide.It is proposed that the anion is produced in its triplet state following photoadiabatic cleavage of the lowest n,?* triplet state of p-nitrophenylacetate.The triplet state of the anion is observed as an intermediate (λmax ca. 290 nm) of lifetime 90 ns (pH > 5.0).In methanol/water and acetonitrile/water mixtures, its lifetime is found to increase as the aqueous portion of the solvent is decreased.A reaction mechanism is developed.
- Craig, Bruce B.,Weiss, Richard G.,Atherton, Stephen J.
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Read Online
- Preparation method 4-4' -dinitrobibenzyl
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The invention discloses a novel method for preparing 4-4’ -dinitrobibenzyl. The method uses p-nitrotoluene as reactant, oxygen is oxidant, ethanol is solvent, the transition metal-doped FDU - 12 mesoporous molecular sieve supported guanidine salt ionic liquid is used as a catalyst, 4, 4' -dinitrobibenzyl is prepared through high-selectivity oxidative dehydrogenation coupling reaction. After completion of the reaction, the catalyst is easily separated from the product phase and can be recycled well. The method has the advantages of simple operation. The method has the advantages of mild reaction conditions, less catalyst consumption, high reaction efficiency and selectivity, less waste of three wastes, and is a novel green cleaning preparation method.
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Paragraph 0044-0066
(2021/11/14)
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- Palladium and Nickel Catalyzed Suzuki Cross-Coupling with Alkyl Fluorides
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Suzuki cross-coupling of benzylic and unactivated aliphatic fluorides with aryl- and alkenylboronic acids has been achieved via mechanistically distinct Pd and Ni catalyzed pathways that outperform competing protodeboronation, β-hydride elimination, and h
- Balaraman, Kaluvu,Wolf, Christian
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supporting information
p. 8994 - 8999
(2021/11/20)
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- Diphenyl ethane diisocyanate and preparation method thereof
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The invention discloses diphenyl ethane diisocyanate and a preparation method thereof, and relates to the technical field of high molecular material monomer preparation. The diphenylethane diisocyanate has a structure shown in the specification, wherein R is H or alkyl, and a substituent R is positioned at a 2 (2') site or a 3 (3') site; substituent -NCO is located at a 4 (4') site or a 5 (5') site or a 6 (6') site; EDI serves as a polyurethane monomer to be applied to polyurethane materials and comprises polyurethane foam, a polyurethane adhesive, polyurethane synthetic leather, a polyurethane fabric coating layer, a polyurethane resin coating, a polyurethane elastomer and other synthetic materials.
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Paragraph 0036
(2020/04/29)
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- The electrochemical behavior of 4-nitrobenzyl bromide and its catalytic activity for reduction of CO2 in the acetonitrile solvent at the Cu/Pd/rGO/GCE surface
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In this study, 4-nitrobenzyl bromide was used as a catalyst for reduction of CO2 and as an initial substrate for electrosynthesis of 4-nitrophenylacetic acid. Cu nanoparticles/Pd nanoparticles/reduced graphene oxide nanocomposite modified glassy carbon electrode (Cu/Pd/rGO/GCE) was used to promote electroactivation of CO2. rGO film was fabricated via electrochemical reduction of dispersed GO nanosheets on the GCE surface. Cyclic voltammetry procedure was applied in two steps to deposit Pd and Cu nanoparticles on the rGO/GCE surface. The morphology and structure of the nanocomposites were characterized using FESEM, EDS, AFM and XRD analysis. FTIR, 1H and 13C NMR spectral characteristics were used to identify the final products of the catalytic process. The electrocarboxylation of 4-nitrobenzyl bromide occurs at a potential which is less negative than those reported for other aryl halides. The results indicate that 4-nitrobenzyl bromide, as a catalyst, plays a dual role in the electrosynthesis of 4-nitrophenylacetate. The dual role includes the electrocatalytic reduction of CO2 and reaction of produced CO2 ?? with 4-nitrobenzyl bromide radical anion. Finally, an EC'C mechanism is proposed for the electrosynthesis of 4-nitrophenylacetate.
- Benvidi, Ali,Ghobadi, Kobra,Khoshro, Hossein,Mohammadzadeh, Safoora,Zare, Hamid R.
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- Novel preparation of N-arylmethyl-N-arylmethyleneamine N-oxides from benzylic bromides with zinc and isobutyl nitrite
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Treatment of benzylic bromides with Zn and LiCl, followed by the reaction with i-butyl nitrite gave N-arylmethyl-N-arylmethyleneamine N-oxides in moderate yields. The present reaction is a novel and simple method for the preparation of nitrones from benzylic bromides, although the yields are moderate.
- Yanai, Kei,Togo, Hideo
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p. 3523 - 3529
(2019/05/24)
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- Dual copper- and photoredox-catalysed C(sp2)-C(sp3) coupling
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The use of copper catalysis with visible light photoredox catalysis in a cooperative fashion has recently emerged as a versatile means of developing new C-C bond forming reactions. In this work, dual copper and photoredox catalysis is exploited to effect C(sp2)-C(sp3) cross-couplings between aryl boronic acids and benzyl bromides.
- McLean, Euan B.,Gauchot, Vincent,Brunen, Sebastian,Burns, David J.,Lee, Ai-Lan
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supporting information
p. 4238 - 4241
(2019/04/30)
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- Perylene-Grafted Silicas: Mechanistic Study and Applications in Heterogeneous Photoredox Catalysis
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A mechanistic study is herein presented for the use of heterogeneous photocatalysts based on perylene moieties. First, the successful immobilization of perylene diimides (PDI) on silica matrices is demonstrated, including their full characterization by means of electronic microscopy, surface area measurements, powder XRD, thermogravimetric analysis, and FTIR, 29Si and 13C solid-state NMR, fluorescence, and diffuse reflectance spectroscopies. Then, the photoredox activity of the material was tested by using two model reactions, alkene oxidation and 4-nitrobenzylbromide reduction, and mechanistic studies were performed. The mechanistic insights into their photoredox activity show they have promising dual photocatalytic activity for both organic oxidations and reductions.
- Carrillo, Adela I.,Elhage, Ayda,Marin, M. Luisa,Lanterna, Anabel E.
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supporting information
p. 14928 - 14934
(2019/12/02)
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- Glass wool: a novel support for heterogeneous catalysis
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Heterogeneous catalysis presents significant advantages over homogeneous catalysis such as ease of separation and reuse of the catalyst. Here we show that a very inexpensive, manageable and widely available material-glass wool-can act as a catalyst support for a number of different reactions. Different metal and metal oxide nanoparticles, based on Pd, Co, Cu, Au and Ru, were deposited on glass wool and used as heterogeneous catalysts for a variety of thermal and photochemical organic reactions including reductive de-halogenation of aryl halides, reduction of nitrobenzene, Csp3-Csp3 couplings, N-C heterocycloadditions (click chemistry) and Csp-Csp2 couplings (Sonogashira couplings). The use of glass wool as a catalyst support for important organic reactions, particularly C-C couplings, opens the opportunity to develop economical heterogeneous catalysts with excellent potential for flow photo-chemistry application.
- Elhage, Ayda,Wang, Bowen,Marina, Nancy,Marin, M. Luisa,Cruz, Menandro,Lanterna, Anabel E.,Scaiano, Juan C.
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p. 6844 - 6852
(2018/09/11)
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- Reductive Homocoupling of Organohalides Using Nickel(II) Chloride and Samarium Metal
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A homocoupling method for organohalides and organosulfonates promoted by samarium metal and HMPA, and catalyzed by NiCl2 has been developed. Various organohalides (benzyl, aryl, heterocyclic, alkenyl and alkyl halides), α-haloacetophenones, and phenyl organosulfonates were tolerated, and the reaction afforded coupling products with high efficiency. Excellent chemoselectivity was exhibited between halides and other groups, such as ?COOH, ?NO2, halogen, heterocyclic ring, ester, and ketone groups. The stereoselectivity suggested that the reaction mechanism might involve an organosamarium species.
- Liu, Yongjun,Xiao, Shuhuan,Qi, Yan,Du, Feng
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p. 673 - 678
(2017/03/22)
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- A well-defined low-valent cobalt catalyst Co(PMe3)4 with dimethylzinc: a simple catalytic approach for the reductive dimerization of benzyl halides
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Herein, we report the first catalytic version of a cobalt-catalysed reductive homocoupling of benzyl halides which proceeds with low catalyst loadings (0.5 to 5 mol%). By synthetizing each cobalt intermediate we demonstrate that reaction proceeds through two single electron transfers (SET) and that dimethylzinc is only involved in the regeneration of the catalytic species.
- Fallon, Brendan J.,Corcé, Vincent,Amatore, Muriel,Aubert, Corinne,Chemla, Fabrice,Ferreira, Franck,Perez-Luna, Alejandro,Petit, Marc
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p. 9912 - 9916
(2016/12/07)
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- Heterogeneous photocatalytic C-C coupling: Mechanism of plasmon-mediated reductive dimerization of benzyl bromides by supported gold nanoparticles
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The use of gold nanoparticles supported on TiO2 (Au@TiO2) as photocatalysts was extended to include photoinduced reductive C-C coupling. Surface plasmon excitation of supported AuNPs in the presence of an amine leads to the C-C coupling of a variety of substituted benzyl bromides at room temperature with good yields in a free radical-mediated reaction. The overall efficiency of the C-C coupling is largely dependent on the nature of the amine used.
- Lanterna, Anabel E.,Elhage, Ayda,Scaiano, Juan C.
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p. 4336 - 4340
(2015/09/01)
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- An amphiphilic, catalytically active, vitamin B12 derivative
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We performed the reaction of vitamin B12 with N,N-dimethylformamide dimethyl acetal for primary amide activation, and added MeOH as a nucleophile, to afford cobalester, the first amphiphilic cobalamin derivative. The unique combination of redox properties and solubility represents an asset for its use as a catalyst in C-C bond forming reactions. This journal is the Partner Organisations 2014.
- Giedyk,Fedosov,Gryko
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supporting information
p. 4674 - 4676
(2014/05/06)
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- Iron nanoparticle-promoted Cu (I)-catalysed homocoupling of arylmethyl halides for the synthesis of 1,2-diarylethanes
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Carbon-carbon bond formation is important in organic synthesis for the preparation of natural products, organic materials and polymers and so on. An efficient and mild reductive homocoupling of arylmethyl halides is now described. Treatment of various benzylic halides in the presence of zero valent iron nanoparticles (nZVI) and a catalytic amount of CuBr in air and water at room temperature afforded 1,2-diarylethanes in excellent yields.
- Shekarriz, Marzieh,Adib, Mehdi,Biabani, Tayebe,Taghipoor, Sohrab
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experimental part
p. 29 - 30
(2012/04/04)
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- Reduction of nitroarenes to azoxybenzenes by NaOH-PEG 400
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The reduction of nitroarenes to azoxybenzenes by NaOH-PEG 400 in benzene is described. The protocol is facile, economical, and effective.
- Liu, Yufang,Liu, Bo,Guo, Ailing,Dong, Zhenming,Jin, Shuo,Lu, Yun
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experimental part
p. 2201 - 2206
(2012/06/16)
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- Synthesis of a novel analytical reagent for the determination of active sites for conjugation on a catalytic aldolase monoclonal antibody
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An optimized and scalable synthesis of a novel analytical reagent for the determination of the number of active sites available for conjugation on a catalytic aldolase monoclonal antibody (mAb) is described. The original conditions suffered from lack of reproducibility, incomplete reactions, and required several chromatographies and lyophilizations that afforded material of low purity. A redesigned route and optimized protocols have been developed that eliminate the use of toxic and unsafe reagents such as HMPA and HATU. In addition, the number of chromatographies has been reduced to only one and time-consuming and energy-intensive lyophilizations are no longer required. The overall yield has been considerably improved from the original 4% to 20% after telescoping the last two steps of the synthesis and this new approach allowed for the preparation of material with higher chemical purity (≥99% vs the initial 90%) to meet specifications.
- Magano, Javier,Farrand, Douglas,Haase, Jeffrey P.,Lovdahl, Michael,Maloney, Mark T.,Pozzo, Mark J.,Teixeira, John J.,Whritenour, David C.,Rizzo, John,Tumelty, David,Bhat, Abhijit,Bradshaw, Curt
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scheme or table
p. 1385 - 1389
(2012/04/04)
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- Facile and efficient reductive homocoupling of benzyl and aryl halides catalyzed by ionic liquid [C12mim][CuCl2] in the presence of metallic zinc and copper
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A facile and efficient synthesis of bibenzyl and biaryl derivatives by reductive homocoupling reaction is described. Treatment of benzyl and aryl halides with metallic zinc and copper powder in the presence of a catalytic amount of [C12mim][CuCl2] under ligand- and base-free conditions gives the corresponding bibenzyls and biaryls in good to high yields. The product can be isolated by a simple extraction with organic solvent, and the catalytic system can be recycled or reused without any significant loss of catalytic activity.
- Hu, Yu-Lin,Li, Fu,Gu, Guo-Liang,Lu, Ming
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experimental part
p. 467 - 473
(2011/12/05)
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- Synthesis of new Schiff base ligands from quinoline and benzo[h]quinoline
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The one-post synthesis of Schiff base ligands that derived from condensation of 4,4'- diamino diphenylsulfone (dapsone) and 4,4'- dinitrobibenzyl and aromatic aldehydes is reported. These compounds can be used to bind various transition metals. The products have been characterized by their IR and 1H NMR spectra.
- Mahmoodi,Asadollahi,Naseri
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body text
p. 1257 - 1264
(2011/10/09)
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- First TDAE-mediated double addition of nitrobenzylic anions to aromatic dialdehydes
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We report herein the first tetrakis(dimethylaminoEthylene (TDAE)-mediated double addition of nitrobenzylic anions to aromatic dialdehydes such as terephthalaldehyde and isophthalaldehyde, and have developed a new methodology that allows us to observe the double addition. This TDAE-mediated approach is an original and mild method with which to generate tri-aromatic diols. Georg Thieme Verlag Stuttgart.
- Juspin, Thierry,Giuglio-Tonolo, Gamal,Terme, Thierry,Vanelle, Patrice
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scheme or table
p. 844 - 848
(2010/09/10)
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- Facile synthesis of bibenzyl by reductive homocoupling of benzyl halides in aqueous media
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A facile synthesis of bibenzyl derivatives by reductive homocoupling reaction is described. Treatment of benzyl halides with metallic iron powder in the presence of a catalytic amount of cuprous salt in aqueous media gives bibenzyls in good yields. Copyright Taylor & Francis Group, LLC.
- Liu, Jian,Li, Bin
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p. 3273 - 3278
(2008/02/12)
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- Generation of Sulfur Ylides from Sulfonium Salts and Their Reactions. Comparative Study of Electrochemical Reduction with the Base Method and Mechanism Elucidation by the MO Method
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The cathodic reduction of sulfonium salts in acetonitrile in the presence and absence of benzaldehyde was carried out. Results were compared with results of the base method. In the presence of benzaldehyde, the electrochemical reduction gave epoxides as a result of the Corey-Chaykovsky reaction, thus confirming ylide formation. The electrochemical reduction of sulfonium salts without benzaldehyde yielded rearrangement products in high yield. On the contrary, upon base treatment of sulfonium salts without benzaldehyde, symmetrical epoxides derived from the benzyl group of the sulfonium salt are obtained as main products as a result of the auto oxidation of the sulfur ylide. The reaction mechanisms were elucidated based on the results obtained by a semi-empirical molecular orbital method.
- Okazaki, Yuichi,Ando, Fumio,Koketsu, Jugo
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p. 2155 - 2165
(2007/10/03)
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- Suzuki cross-coupling reaction of benzylic halides with arylboronic acids in the presence of a tetraphosphine/palladium catalyst
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The cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl) cyclopentane-[PdCl(C3H5)]2 system catalyses efficiently the Suzuki cross-coupling reaction of benzylic halides with arylboronic acids. A wide variety of benzylic bromides or chlorides and functionalised arylboronic acids lead selectively to the corresponding diarylmethane adducts in good yields. Furthermore, this catalyst can be used at low loading in many cases.
- Chahen, Ludovic,Doucet, Henri,Santelli, Maurice
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p. 1668 - 1672
(2007/10/03)
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- Direct preparation of benzylic manganese reagents from benzyl halides, sulfonates, and phosphates and their reactions: Applications in organic synthesis
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The use of highly active manganese (Mn)*, prepared by the Rieke method, was investigated for the direct preparation of benzylic manganese reagents. The oxidative addition of the highly active manganese to benzylic halides was easily completed under mild conditions. Moreover, benzylic manganese sulfonates and phosphates were prepared by direct oxidative addition of Mn* to the carbon-oxygen bonds of benzylic sulfonates and phosphates. The resulting benzylic manganese reagents were found to undergo cross-coupling reactions with a variety of electrophiles. Most of these reactions were carried out in the absence of any transition metal catalyst under mild conditions. In addition, the use of highly active manganese was also studied for preparation of homo-coupled products of functionalized benzyl halides without transition metal catalysts. These useful approaches provided not only a facile synthetic route to the preparation of resoricinolic lipids but a facile synthesis of functionalized 4-benzylpyridines by regioselective and chemo selective γ-addition of benzylic group to N-alkoxycarbonylpyridinum salts.
- Suh, YoungSung,Lee, Jun-Sik,Kim, Seoung-Hoi,Rieke, Reuben D.
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- Co-C bond cleavage in the reactions of alkyl, benzyl and heteroaromaticmethyl cobaloximes with arene sulfenyl chloride: Homolytic and heterolytic pathways
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The reactions of arene sulfenyl chlorides, ArSCl, (Ar=Ph, C6Cl5, 2,4 (NO2)2C6H3) with organocobaloximes, RCo(dmgH)2Py, (R=alkyl, benzyl and heteroaromaticmethyl) were carried out under thermal and photochemical conditions. A variety of organic and organometallic products are formed depending upon the substrate cobaloxime. For 3-methoxybenzyl and heteroaromaticmethyl cobaloximes the results suggest that they represent a unique class of cobaloximes whereby both the aromatic ring as well as the Co-C bond are highly activated towards attack by the arene sulfenyl chloride. Both homolytic as well as heterolytic pathways are operative.
- Gupta,Dixit, Vandana,Das, Indira
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- Radical ion reactions of carbanions derived from 4-nitro-, 2,4-dinitro-, and 2,4,6-trinitrotoluenes with polynitroalkanes
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4-Nitro-and 2,4-dinitrotoluenes react with tetranitro-and halotrinitromethanes in the presence of bases to give the corresponding nitro-substituted 1,2-diphenylethanes and stilbenes. Reactions of 2,4,6-trinitrotoluene with fluorotrinitromethane, N,N-dinitrotnethylamine, and tert-butyl and isopropyl nitrates result in formation of α,2,4,6-tetranitrotoluene; with chlorotrinitromethane, 2,4,6-trinitrobenzyl chloride is formed.
- Makarevich,Shcherbinin,Bazanov,Tselinskii
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p. 684 - 692
(2007/10/03)
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- Aromatic aldehydes from benzylbromides via Cobalt(I) mediated benzyl radicals in the presence of aerial oxygen: A mild oxidation reaction in neutral condition
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Co(PPh3)3Cl has been shown to be a novel mediator for the conversion of benzylic bromides to aromatic aldehydes under mild conditions in the presence of acnal oxygen probably via benzylic radicals. In the absence of oxygen, the carbon-carbon coupling reactions have been utilised to attend a series of functionalised benzylic dimers.
- Goswami, Shyamaprosad,Mahapatra, Ajit Kumar
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p. 1981 - 1984
(2007/10/03)
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- Reactivity of the acids of trivalent phosphorus and their derivatives. Part IX. The > P-O- and > p-s- nucleophiles in the reactions of halophilic substitution
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The reaction of the > P-Y- (Y = O; S) nucleophiles with the compounds possessing a C-Br bond and electron-withdrawing groups is described. The isolation of the products derived from dialkyl bromophosphates, the results of the 31P NMR studies, as well as the isolation of bromothiophosphate from the reaction mixture of > P-S- nucleophile and methyl α-bromocarboxylate, are further evidence for halophilic substitution as the principal process in the X-philic substitution/SET tandem mechanism operating in the reaction of these phosphorus nucleophiles with the bromoderivatives possessing electron-withdrawing groups.
- Dembkowski, Leszek,Witt, Dariusz,Rachon, Janusz
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p. 143 - 157
(2007/10/03)
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- Ozone-mediated nitration of bicumene and derivatives with nitrogen dioxide. Preferential mesolytic bond cleavage over nuclear nitration in evidence for the electron transfer nature of the kyodai-nitration of arenes
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The ozone-mediated reaction of bicumene and some derivatives 1 with nitrogen dioxide in dichloromethane at low twmperatures resulted in the facile cleavage of the central C-C bond to give the corresponding benzyl nitrate and its descendants 4-6. mesolytic bond cleavage occured almost exclusively over nuclear substitution at temperatures as low as -20 deg C, especially at low concentration (2 x 10-3 mol dm-3).This result may be rationalized in terms of initial electron transfer between the aromatic substrate and nitrogen trioxide in situ to form the aromatic radical cation, which then undergoes C-C bond scission at the benzylic position.In contrast, bibenzyl 2a is simply nitrated on the aromatic ring under similar conditions, giving the expected nitration products 7 and 8a-c along with a small amount of benzaldehyde 9.Results obtained from semi-empirical calculations and cyclic voltammetry are also in accord with the electron transfer nature of the reaction.The C-Si bond fission of benzyltrimethylsilane, C-C bond fragmentation of cyclic acetals of aromatic carbonyl compounds as well as side-chain reactions of toluene and derivatives, have all previously been observed under certain conditions of the kyodai-nitration and can be understood on a similar basis as described above.The possible involment of electron transfer processes in aromatic nitration with acetyl nitrate has also been suggested.
- Suzuki, Hitomi,Mori, Tadashi
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p. 1265 - 1274
(2007/10/03)
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- Reactivity of the acids of trivalent phosphorus and their derivatives. Part VI. The reaction of the >P-O- anions with benzyl bromides para-substituted in the phenyl ring
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The reaction of p-substituted benzyl bromides with the >P-O- ions in THF, alcohols and toluene as the solvents is described. According to the reduction potential of the p-substituted benzyl bromides and the solvent used the formation of the P-C bond, debromination and/or dimerization occur. The principal process is believed to be X-philic substitution, the dimers are formed through a secondary process via SET from the p-substituted benzyl anions into the p-substituted benzyl bromides.
- Witt, Dariusz,Rachon, Janusz
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p. 169 - 187
(2007/10/03)
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- Substituent effects on the photocleavage of benzyl-sulfur bonds. Observation of the "Meta effect"
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Benzyl phenyl sulfide has been used to investigate the photocleavage mechanism for benzyl-sulfur bonds. Four experiments have shown that the reaction goes through a radical intermediate. First, the photoproducts observed can all be justified by radical mechanisms. Second, the radical intermediate was trapped with a five hexenyl tether. Third, UV analysis of analogs for the 4-NO2 derivative indicate no exciplex or electron transfer pathway. Fourth, no strong correlation is observed between a values and the quatum yields for loss of substituted benzyl phenyl sulide. The effect of oxygen on quantum yields is best observed after samples are thoroughly outgassed with consecutive freeze-pump-thaw cycles. It is shown that oxygen diminishes the substituent effect. Upon photolysis of the outgassed samples, the meta-substituted derivatives showed more significant variances than the para derivatives. The meta derivatives are most efficiently cleaved in the following order: 3-CN > 3-NO2 > 3-CF3 > 3-CH3 > 3-OCH3. These findings are justified by an increase in electron density of the radical ipso to the forming benzyl radical for the 3-OCH3 derivative and a decrease in the electron density of the radical ipso to the forming benzyl radical for the 3-CN derivative.
- Fleming, Steven A.,Jensen, Anton W.
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p. 7040 - 7044
(2007/10/03)
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- REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEIR DERIVATIVES. PART IV. THE REACTION OF DIALKYLPHOSPHITE ANIONS WITH NITROBENZYL BROMIDES
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The reaction of o-, m- and p-nitrobenzyl bromide with sodium dimethylphosphite as well as sodium diisopropylphosphite in THF and alcohols as the solvent is described.According to the constitution of the starting materials and the solvents used, the formation of the P-C bond, debromination or dimerization occurs.The principal process in o- and p-nitrobenzyl bromide and >P-O- anion systems is believed to be X-philic substitution, the dimer is formed through a secondary process via SET from the nitrobenzyl anion to nitrobenzyl bromide.Electron-transfer and proton-transfer processes in the nitrobenzyl bromide->P-O- systems are also discussed.Key words: o-, m- and p-nitrobenzyl bromides, dialkyl phosphites, Michaelis-Becker reaction, X-philic substitution, SET.
- Witt, Dariusz,Rachon, Janusz
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- REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEUR DERIVATIVES. PART II. THE REACTION OF TRIVALENT PHOSPHORUS ACID SALTS WITH THE BENZYLIC HALIDES SYSTEM
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The reaction of the benzylic halides systems with sodium dialkylphosphites as well as the sodium salt of dibenzylphosphine oxide in THF and alcohols as the solvents is described.According to the constitution of the starting materials, the formation of the P-C bond, dehalogenation or dimerization occurs.Probable mechanisms namely SET and X-philic substitution are discussed.Key words: Benzylic halides system, dialkylphosphites, dibenzylphosphine oxide, Michaelis-Becker reaction, X-philic substitution.
- Witt, Dariusz,Rachon, Janusz
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p. 153 - 164
(2007/10/02)
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- Incorporation of CO and NO Ligands in the Reaction of Benzyl Bromides with Tetrabutylammonium Tricarbonylnitrosylferrate
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Reaction of benzyl bromides with tetrabutylammonium tricarbonylnitrosylferrate afforded N-benzylphenylacetamides via incorporation of CO and NO ligands accompanied with dibenzyl ketones.A noticeable substituent effect on the amide-forming reaction was observed.
- Nakanishi, Saburo,Shimizu, Yasuyo
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p. 1925 - 1926
(2007/10/02)
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- Photocleavage of Benzyl-Sulfide Bonds
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The nucleoside transport inhibitor 6--9-(β-D-ribofuranosyl)purine, NBMPR, has been used successfully in photoaffinity labeling.We have studied the mechanism for photocleavage of the benzyl-sulfur bond by using substituted benzyl phenyl sulfides as analogues of NBMPR.This has enabled us to enhance the photoreactivity of the benzyl-sulfur bond.We have also performed "radical clock" studies with a hexenyl side chain to trap reactive intermediates.The mechanistic interpretation from the substituent and side chain studies is that the benzyl-sulfur moiety is photocleaved via a homolytic pathway.
- Fleming, Steven A.,Jensen, Anton W.
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p. 7135 - 7137
(2007/10/02)
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- Homolytic displacement at saturated carbon in organocobaloximes: Part VI - Synthesis of benzyl sulphones
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The reactions of thiophene-2-sulphonyl chloride with benzyl and para-substituted benzyl cobaloximes under anaerobic and photochemical conditions at 0 deg C give benzyl sulphones and bibenzyls in variable yields.However, the reactions with heteroaromatic methyl cobaloximes give the corresponding sulphones as the exclusive organic products.The reactions are interpreted in terms of SH2 mechanism.
- Gupta, B. D.,Das, Indira,Dixit, Vandana
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p. 762 - 766
(2007/10/02)
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- Electron-transfer versus Nucleophilic Substitution in the Reactions of α-Halogenated 4-Nitrotoluenes with Base
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A comparative study of the reactions of 4-nitrobenzyl and 4-nitrobenzylidene halides (ArCHXY; Ar = 4-NO2C6H4-; X = H or Halogen; Y = Halogen) with alkali shows that the reaction is sensitive to the nature of the side chain halogen substituent(s) as well as the reaction conditions.In alcoholic alkali, only 4-nitrobenzyl chloride (ArCH2Cl) reacts smoothly via the electron transfer (ET)-radical pathway to give mainly dimeric products while the corresponding bromide (ArCH2Br) and iodide (ArCH2I) give exclusively SN products.The ET pathway is enhanced for these substrates by the application of phase-transfer catalysis.In the case of the 4-nitrobenzylidene dihalides (ArCHXY; X = Y = Cl; X = Cl, Y = Br; X = Y = Br; X = F, Y = Br) it is also shown that although progressive bromine substitution suppresses the ET pathway, application of phase-transfer catalysis minimises competing solvolytic reactions and enhances the radical reaction.
- Kam, Toh-Seok,Lim, Tuck-Meng
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p. 147 - 150
(2007/10/02)
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- Photochemical Dissociation of p-Nitrobenzyl Sulfonate Esters via an Intramolecular Electron Transfer
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The photochemistry of p-nitrobenzyl sulfonate esters, p-nitrobenzyl 5-dimethylaminonaphthalene-1-sulfonate (NDS) and p-nitrobenzene pyrene-1-sulfonate (NPS) has been investigated by both steady-state and laser flash photolysis techniques.These sulfonates are photochemically dissociated to give the parent sulfonic acids.Quantum yields for photodissociation of NDS and NPS with excitation at 365 nm in degassed acetonitrile solution are 0.20 +/- 0.05 and 0.16 +/- 0.04, respectively.Photodissociation of these sulfonates is considered to proceed via an intramolecularelectron transfer from the excited singlet state of the 5-dimethylaminonaphthalene or pyrene moiety to the p-nitrobenzyl moiety from the fact that the transient absorption bands at 390 and 550 nm due to the radical cation of the 5-dimethylaminonaphthalene moiety, 420 and 450 nm due to the radical cation of the pyrene moiety, and at 340 nm due to the radical anion of the p-nitrobenzyl moiety are detected in laser spectroscopy.Intramolecular-electron-transfer-induced bond cleavage is observed at the oxygen-carbon bond of these sulfonate esters, producing the organic strong acids.Although photodissociation of o-nitrobenzyl esters of carboxylic and sulfonic acids is known, that of p-nitrobenzyl esters has not been previously reported.From the mechanistic point of view, the photochemical behaviour of these p-nitrobenzyl sulfonate esters is quite different from that of o-nitrobenzyl esters.While the latter involves a photoinduced intramolecular rearrangement, the former involves a photoinduced intramolecular electron transfer.
- Naitoh, Kazuhiko,Yamaoka, Tsuguo
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p. 663 - 670
(2007/10/02)
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- Photoinduced Intramolecular Electron Transfer Mechanism for Photochemical Dissociation of Para-Substituted Benzyl 9,10-Dimethoxyanthracene-2-sulfonates
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The photochemical behavior of para-substituted benzyl 9,10-dimethoxyanthracene-2-sulfonates with varying electron-withdrawing ability of substituents has been investigated by both steady-state and laser flash photolysis techniques. p-Nitrobenzyl 9,10-dimethoxyanthracene-2-sulfonate is photochemically dissociated to give 9,10-dimethoxyanthracene-2-sulfonic acid, 9,10-dimethoxy-2-(p-nitrobenzyl)anthracene, and p,p'-dinitrobibenzyl which were assigned on the basis of mass spectroscopic data and 1H NMR spectroscopy.Quantum yields for the photodissociation of p-nitrobenzyl 9,10-dimethoxyanthracene-2-sulfonate and for the formation of 9,10-dimethoxyanthracene-2-sulfonic acid with excitation at 436 nm in degassed acetonitrile solution are 0.12 +/- 0.03 and 0.10 +/- 0.03, respectively.Photodissociation of p-nitrobenzyl 9,10-dimethoxyanthracene-2-sulfonate is considered to proceed via an intramolecular electron transfer from the excited singlet state of 9,10-dimethoxyanthracene moiety to p-nitrobenzyl moiety followed by the heterolytic bond cleavage at oxygen-carbon bond of the sulfonyl ester from the fact that the transient absorptions at 310 and 425 nm due to 9,10-dimethoxyanthracene-2-sulfonate radical cation and around 340 nm due to the p-nitrobenzyl radical anion are detected in laser spectroscopy.The rate constant for dissociation of p-nitrobenzyl 9,10-dimethoxyanthracene-2-sulfonate was determined to be (1.1 +/- 0.5) * 105 s-1 by kinetic analyses.Possible mechanisms for the photodissociation are discussed and it is concluded that the three factors which control the rate of photodissociation are intramolecular electron transfer, feasibility of oxygen-carbon bond scission, and stability of benzyl-type radical formed by the photodissociation.
- Naitoh, Kazuhiko,Yoneyama, Koh,Yamaoka, Tsuguo
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p. 238 - 244
(2007/10/02)
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- Homolytic Displacement at Saturated Carbon in Organocobalamines. Part 4
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Benzyl and para-substituted benzylcobaloximes react with substituted arenesulphonyl chlorides under photochemical and anaerobic conditions at 0 deg C to give a variety of products including the sulphones, bibenzyls, and benzyl ethers of dimethylglyoxime in variable yields.However, when the reactions are carried out in the presence of a 1 mol excess of pyridine, the yield of sulphones is increased by at least 20percent in each case.The corresponding yield of bibenzyls is decreased and no trace of the benzyl ether of dimethylglyoxime is formed.On the other hand, the reaction of heteroaromatic methyl cobaloximes with arenesulphonyl chlorides form the corresponding sulphones as the exclusive organic product in good yield and with no side products.The reactions are interpreted in terms of a direct attack of the arenesulphonyl radical on the α carbon of the benzyl and heteroaromatic methyl ligand.
- Gupta, B. Dass,Roy, Maheswar,Roy, Sujit,Kumar, Manoj,Das, Indira
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p. 537 - 543
(2007/10/02)
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- Photochemical Dissociation of p-Nitrobenzyl 9,10-Dimethoxyanthracene-2-sulphonate via Intramolecular Electron Transfer
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While o-nitrobenzyl aromatic sulphonates are known to photodissociate via an intramolecular rearrangement, photodissociation of p-nitrobenzyl aromatic sulphonates has not been reported.In this study, we report that p-nitrobenzyl 9,10-dimethoxyanthracene-2-sulphonate is photochemically dissociated to give 9,10-dimethoxyanthracene-2-sulphonic acid, 9,10-dimethoxy-2-(p-nitrobenzyl)-anthracene, and p,p'-dinitrobibenzyl.The dissociation is considered to proceed via an intramolecular electron transfer from the 9,10-dimethoxyanthracene moiety to the p-nitrobenzyl moiety.The quantum yield of the photodissociation in acetonitrile is 0.11 and the spectral response extends to 450 nm.The quantum yield is much higher than those of o-nitrobenzyl esters.
- Yamaoka, Tsuguo,Adachi, Hiroshi,Matsumoto, Kazuo,Watanabe, Hiroo,Shirosaki, Tsutomu
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p. 1709 - 1714
(2007/10/02)
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- Elektrosynthese von 2,2'-Dinitrobenzyl aus 2-Nitrobenzylbromid. Mechanistische und praeparative Untersuchungen
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The mechanism of the electrochemical reduction of 2-nitrobenzyl halides in aprotic media has been reinvestigated by electroanalytical methods (dc-polarography, cyclic voltammetry, potentiostatic coulometry, rotating ring-disk electrode), by using NICHOLSON-SHAIN criteria and product analysis by gas chromatography.The cathodic reduction of 2-nitrobenzyl halides proceeds via the mechanism EC1irr.On the basis of cyclic voltammetric data the rate constant of the cleavage of the anion radical of 2-nitrobenzyl bromide (k1 = 59,6 sec-1) and of 4-nitrobenzyl bromide (k1 = 144 sec-1) in 0,1M (C2H5)4NClO4/acetonitrile at 25 deg C has been determined.The one-electron reduction of 2-nitrobenzyl halides and the subsequent decomposition of the anion radical lead to the neutral 2-nitrobenzyl radical, which dimerizes to 2,2'-dinitrodibenzyl.The electropreparative investigations by galvanostatic and potentiostatic electrolyses showed that the best method of electrosynthesis of 2,2'-dinitrodibenzyl from 2-nitrobenzyl bromide is the controlled-potential electrolysis (mercury pool-electrode, 0,1M (C2H5)4NClO4/acetonitrile, E = -1.0...-1.1V (SCE), Q = 1.1 Faraday per mole, yield 93-95percent).
- Vieth, B.,Jugelt, W.,Pragst, F.
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p. 338 - 352
(2007/10/02)
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- Kinetic and Spectral Properties of the Photogenerated p-Nitrobenzyl Carbanion in Aqueous Media
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The p-nitrobenzyl carbanion is a photoelimination product from various p-nitrobenzyl (p-NO2C6H4CH2R, R = CO2-, PO32-, CH2OH, etc.) compounds in aqueous media.Following millisecond flash photolysis of N2-saturated p-nitrophenylacetate (pH > 6) solutions, we have shown that the carbanion decays via mixed first-(solvent protonation) and second-(dimerisation) order processes.Rate constants k1 = 1.3 +/- 0.1 * 10-2 s-1 and 2k2 = 1.7 +/- 0.3 * 103 dm3 mol-1 s-1, respectively, are determined.Reactions of the anion with O2, H+, and an efficient one-electron oxidant, IrCl62-, are also examined.Studies in dimethyl sulphoxid-water mixtures indicate that the anion exists as a hydrated form (γmax 356 nm) in water and an 'unspecifically' solvated species in dimethyl sulphoxide (γmax ca. 440 nm).A reaction mechanism is developed which accounts for transformation of the carbanion to p,p'-dinitrobibenzyl and p-nitrotoluene, the major isolable nitro products from these systems.
- Craig, Bruce B.,Atherton, Stephen, J.
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p. 1929 - 1936
(2007/10/02)
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- Sructure an Mechanism in the Photo-Retro-Aldol Type Reactions of Nitrobenzyl Derivatives. Photochemical Heterolytic Cleavage of C-C Bonds
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The photo-retro-aldol type reactions of several nitroaromatic compounds have been studied in aqueous solution over the pH 1-14 range.These reactions are observed only in aqueous or in predominantly aqueous solution.Catalysis of reaction due to hydroxide ion is observed for several derivatives.Quantum yields of reaction and product ratios (of nitrotoluene vs dinitrobibenzyl) are reported as a function of pH.The proposed mechanism of reaction involves heterolytic cleavage of the benzylic C-C bond from the triplet excited state in the primary photochemical step to generate a nitrobenzyl carbanion and a carbocation-equivalent fragment, except for the nitrophenylacetates 24-26, which eliminate CO2 in place of such a fragment.Photogenerated nitrobenzyl carbanions are efficiently trapped by molecular oxygen to give isolable hydroperoxides at pH 9 M-1 s-1.The results show that photochemical C-C bond heterolysis requires favorable stabilization of both the carbanion and carbocation-derived fragments.Hydroxide ion catalysis may also facilitate the process.The use of the nitrobenzyl moiety as the carbanion-stabilizing group appears to be generally applicable, as demonstrated by the systems studied.
- Wan, Peter,Muralidharan, S.
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p. 4336 - 4345
(2007/10/02)
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- Le composes d'insertion du graphite comme precurseurs de metaux finement divises I. Couplage d'halogenures benzyliques
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The reduction of a nickel salt by the intercalation compound KC8, results in highly dispersed nickel on graphite, which has been used as a coupling reagent for benzyl chloride.The yield and the selectivity of the reaction were slightly improved when nickel-copper bimetallic clusters were used.The properties of these mixtures are illustrated by the coupling of various substituted benzyl halides.Functional groups such as methoxy-, chloro-, bromo-, nitro-, cyano-, trifluoromethyl- and alkoxy-carbonyl groups, on the aromatic ring, were not affected by the conditions employed.
- Marceau, P.,Beguin, F.,Guillaumet, G.
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p. 137 - 142
(2007/10/02)
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- Method for preparing nitrobibenzyl systems
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Method for preparing bibenzyl systems with nitro groups as substituents. Toluene derivates with nitro groups are coupled oxidatively in methanolic alkali solution under influence of metal catalysts. The oxidation is preferably done with air. As catalysts metal acetonylacetonates are used. The metal can be Ni, Cu, Co, Mn, Cr or Ti. This catalyst can be used together with a crown ether. Another suitable catalyst is a metal tetraphenylporphin of porfyrin type where the metal can be Ni, vanadium (V=O) or Fe(FeIII).
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- Organic Reactions of Reduced Species of Sulfur Dioxide
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Rongalite (sodium hydroxymethanesulfinate or sodium formaldehydesulfoxylate) reacts with organic halides in a variety of ways depending on the structure of the organic compound.Benzyl and other alkyl halides give sulfones in generally good yields; but in several cases, reduction (2,4-dinitrobenzyl bromide, phenacyl halides) or coupling (p-nitrobenzyl bromide under basic conditions, phenacyl bromide or iodide) of the halide occurs.Addition of sodium iodide to the mixture of Rongalite and phenacyl chloride changed the reaction from one of complete reduction to acetophenone to one of mainly dimerization to 1,4-diphenyl-1,4-butanedione.The amount of acetophenone from phenacyl bromide depends on the water content of the reaction mixture, more dimer being formed when little water is present.Diphenacyl sulfone is formed from phenacyl bromide and Rongalite in the presence of excess sulfur dioxide.The intermediate β-keto sulfinate is believed to normally lose sulfur dioxide very readily to give the enolate anion, which either is protonated to give acetophenone or reacts with phenacyl halide to give the butanedione.In the presence of excess sulfur dioxide, the loss of sulfur dioxide from the sulfinate is supressed, allowing sulfone formation to occur by reaction of the sulfinate with phenacyl halide. o-Xylylene dibromide gave o-xylylene, trapped as the Diels-Alder adduct with norbornene, along with the expected cyclic sulfone and cyclic sulfinate ester (sultine).A convenient synthesis of the sultine in 78percent yield is achieved by treatment of α,α'-dichloro-o-xylene with Rongalite and sodium iodide.Treatment of Rongalite in DMF-H2O with sulfur dioxide gives the blue anion radical complex (SO2)(SO2.-).Anion radicals are produced from p-dinitrobenzene and p-nitrobenzoate ion when they are treated with Rongalite.
- Jarvis, William F.,Hoey, Michael D.,Finocchio, Alfred L.,Dittmer, Donald C.
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p. 5750 - 5756
(2007/10/02)
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