- Reactions of benzyltriphenylphosphonium salts under photoredox catalysis
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The development of benzyltriphenylphosphonium salts as alkyl radical precursors using photoredox catalysis is described. Depending on substituents, the benzylic radicals may couple to form C-C bonds or abstract a hydrogen atom to form C-H bonds. A natural product, brittonin A, was also synthesized using this method.
- Boldt, Andrew M.,Dickinson, Sidney I.,Ramirez, Jonathan R.,Benz-Weeden, Anna M.,Wilson, David S.,Stevenson, Susan M.
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supporting information
p. 7810 - 7815
(2021/09/28)
-
- Skeletal editing through direct nitrogen deletion of secondary amines
-
Synthetic chemistry aims to build up molecular complexity from simple feedstocks1. However, the ability to exert precise changes that manipulate the connectivity of the molecular skeleton itself remains limited, despite possessing substantial potential to expand the accessible chemical space2,3. Here we report a reaction that ‘deletes’ nitrogen from organic molecules. We show that N-pivaloyloxy-N-alkoxyamides, a subclass of anomeric amides, promote the intermolecular activation of secondary aliphatic amines to yield intramolecular carbon–carbon coupling products. Mechanistic experiments indicate that the reactions proceed via isodiazene intermediates that extrude the nitrogen atom as dinitrogen, producing short-lived diradicals that rapidly couple to form the new carbon–carbon bond. The reaction shows broad functional-group tolerance, which enables the translation of routine amine synthesis protocols into a strategy for carbon–carbon bond constructions and ring syntheses. This is highlighted by the use of this reaction in the syntheses and skeletal editing of bioactive compounds.
- Kennedy, Sean H.,Dherange, Balu D.,Berger, Kathleen J.,Levin, Mark D.
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p. 223 - 227
(2021/05/19)
-
- Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds
-
We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)3(PMe3)2] (1), supported by weakly coordinating [BArF20] anions, [1·M][BArF20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)3(PMe3)2][BArF20], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1·M][BArF20] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation.
- Tinnermann, Hendrik,Sung, Simon,Csókás, Dániel,Toh, Zhi Hao,Fraser, Craig,Young, Rowan D.
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supporting information
p. 10700 - 10708
(2021/07/31)
-
- Simpler and Cleaner Synthesis of Variously Capped Cobalt Nanocrystals Applied in the Semihydrogenation of Alkynes
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Unlike the classical organometallic approach, we report here a synthetic pathway requiring no reducing sources or heating to produce homogeneous hexagonal-close-packed cobalt nanocrystals (Co NCs). Involving a disproportionation process, this simple and fast (6 min) synthesis is performed at room temperature in the presence of ecofriendly fatty alcohols to passivate Co NCs. Through a recycling step, the yield of Co NCs is improved and the waste generation is limited, making this synthetic route cleaner. After an easy exchange of the capping ligands, we applied them as unsupported catalysts in the stereoselective semihydrogenation of alkynes.
- Moisset, A.,Petit, C.,Petit, M.,Salzemann, C.,Sodreau, A.,Vivien, A.
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supporting information
p. 13972 - 13978
(2020/10/09)
-
- The synergy between the CsPbBr3nanoparticle surface and the organic ligand becomes manifest in a demanding carbon-carbon coupling reaction
-
We demonstrate here the suitability of CsPbBr3nanoparticles as photosensitizers for a demanding photoredox catalytic homo- and cross-coupling of alkyl bromides at room temperature by merely using visible light and an electron donor, thanks to the cooperative action between the nanoparticle surface and organic capping.
- Casadevall, Carla,Claros, Miguel,Galian, Raquel E.,Lloret-Fillol, Julio,Pérez-Prieto, Julia,Rosa-Pardo, Ignacio,Schmidt, Luciana
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supporting information
p. 5026 - 5029
(2020/05/18)
-
- Synthesis of dimeric molecules via ag-catalyzed electrochemical homocoupling of organic bromides paired with electrooxidation of urea
-
We present a sacrificial anode-free approach to reductive homocoupling of organohalides that does not require a co-catalyst. In this approach, a divided electrochemical cell with aprotic and aqueous compartments separated by an anion exchange membrane enables coupling of the cathodic homocoupling reaction with anodic oxidation of urea. We show that, in contrast with traditional one-compartment cells relying on sacrificial anodes, the proposed cell configuration maintains stable cell voltage in the course of galvanostatic electrolysis. A synthetic potential of this method was assessed using a series of 13 organic bromides that demonstrated a strong dependence of the reaction outcome on the structure of the organic substrate, more specifically, the dissociation energy of the C–Br bond and the redox properties of formed radicals, which are discussed in detail. While not being suitable for the synthesis of byarylstructures, this method is excellent for C(sp3)-C(sp3) coupling to corresponding dimeric products with up to quantitative yields. Simultaneous electrochemical treatment of nitrogenous waste in the adjacent half-cell provides an additional incentive for wide adaptation of this sustainable synthetic approach.
- Klinkova, Anna,Krivoshapkina, Elena F.,Medvedev, Jury J.,Medvedeva, Xenia V.,Pivovarova, Yekaterina,Steksova, Yulia P.
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-
- Novel preparation of N-arylmethyl-N-arylmethyleneamine N-oxides from benzylic bromides with zinc and isobutyl nitrite
-
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
-
p. 3523 - 3529
(2019/05/24)
-
- Visible-Light-Driven Self-Coupling of Methylarenes Catalyzed by Ni2P?Cd0.5Zn0.5S Nanoparticles
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The Ni2P?Cd0.5Zn0.5S nanoparticles photocatalyzed self-coupling of p-xylene was reported here, and the corresponding coupling product 1,2-di-p-tolylethane was obtained. The reaction could be extended to toluene derivatives with electron-donating and electron-withdrawing substituents. Ni2P?Cd0.5Zn0.5S nanoparticles had already been characterized by XRD, ICP-AES, SEM, TEM, UV/Vis, FL, XPS. The Mott–Schottky curves of Ni2P?Cd0.5Zn0.5S were made through electrochemical methods. An active carbon free-radical was captured through ESR measurement under irradiation. The research demonstrated this photocatalytic system feasible for the self-coupling reaction of toluene derivatives.
- Yang, Dan-Dan,Hu, Jia-Jun,Zhang, Hong,Lv, Xiao-Jun,Chen, Yong,Fu, Wen-Fu
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p. 1384 - 1392
(2020/01/08)
-
- o-Nitrobenzyl photoremovable groups with fluorescence uncaging reporting properties
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o-Nitrobenzyl (o-NB) derivatives are the most widely applied photoremovable groups for the study of dynamic biological processes. By introducing different substituents to the benzylic position we were able to generate a fluorescence signal upon irradiatio
- Abou Nakad,Bolze,Specht
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p. 6115 - 6122
(2018/09/06)
-
- Silver-Catalyzed Decarboxylative Couplings of Acids and Anhydrides: An Entry to 1,2-Diketones and Aryl-Substituted Ethanes
-
Silver-catalyzed oxidative decarboxylative couplings of carboxylic acids and anhydrides to produce 1,2-diketones and substituted ethanes were developed. This reaction allows the generation of acyl or alkyl radicals by decarboxylation of the corresponding α-keto acids, alkyl acids and anhydrides, which are sequentially coupled to efficiently construct a new C?C bond. This reaction represents a carboxylic acid decarboxylative alternative that employs a radical termination strategy. (Figure presented.).
- Zou, Hua-Xu,Li, Yang,Yang, Yuan,Li, Jin-Heng,Xiang, Jiannan
-
supporting information
p. 1439 - 1443
(2018/02/26)
-
- Dimerization of Benzyl and Allyl Halides via Photoredox-Mediated Disproportionation of Organozinc Reagents
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Benzyl and allyl halides undergo homocoupling when treated with zinc in the presence of a catalytic amount of a cationic iridium(III) complex under irradiation with 400 nm light-emitting diodes. The reaction proceeds through the intermediate formation of an organozinc reagent, which disproportionates to a free radical and elemental zinc under photoredox conditions.
- Levin, Vitalij V.,Agababyan, Daniil P.,Struchkova, Marina I.,Dilman, Alexander D.
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p. 2930 - 2935
(2018/05/28)
-
- 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)
-
- Cyclopentadienyl nickel(ii) N, C-chelating benzothiazolyl NHC complexes: Synthesis, characterization and application in catalytic C-C bond formation reactions
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Cyclopentadienyl (Cp) Ni(ii) complexes [CpNiL][PF6] containing hybrid N,C chelating benzothiazolyl NHC ligands (L1 = 1-(2-benzothiazolyl)-3-methylimidazol-2-ylidene, 3a; L2 = 1-(2-benzothiazolyl)-3-allylimidazol-2-ylidene, 3b; L3 = 1-(2-benzothiazolyl)-3-benzylimidazol-2-ylidene, 3c) have been synthesized and fully characterized. The catalytic activity of 3a-3c in some C-C bond formation reactions has been examined. They are efficient catalysts for the homo-coupling of benzyl bromide in the presence of MeMgCl at r.t. with good functional group tolerance. Complex 3a is active in the catalytic oxidative homo-coupling of Grignard reagents with 1,2-dichloroethane as an oxidant at r.t.
- Teo, Wei Jie,Wang, Zhe,Xue, Fei,Andy Hor,Zhao, Jin
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p. 7312 - 7319
(2016/06/01)
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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
-
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)
-
- EPIDITHIODIKETOPIPERAZINE COMPOUNDS, COMPOSITIONS, AND METHODS
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Epidithiodiketopiperazine compounds, pharmaceutical compositions based thereon and methods of their synthesis, as part of treating, inhibiting and reducing transcription and translation of hypoxia inducible genes are described. In another aspect, the present disclosure describes a method for interfering with hypoxia-induced transcriptional pathway in a cell comprising: contacting the cell with at least one compound disclosed herein. In another aspect, the present disclosure describes a method for treating breast cancer, a solid cancer, a blood cancer, a subject suffering from carcinoma in need of said treatment, and renal cell carcinoma (RCC), comprising: administering to the subject an effective amount of at least one compound disclosed herein. In some embodiments of the methods described herein, the method further comprises administering an additional anti-cancer and/or cytotoxic agent.
- -
-
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- Csp3-Csp3 homocoupling reaction of benzyl halides catalyzed by rhodium
-
A highly reactive alkylrhodium complex was formed from Me2Zn and RhCl(PPh3)3 and effectively catalyzed a Csp 3-Csp3 homocoupling reaction of benzyl halides. A Csp 3-Csp3 coupling reaction using Rh catalyst has not been reported up to now. The reaction proceeded under very mild conditions and gave the corresponding homocoupling products even if they had reactive substituents such as an uncovered formyl or hydroxymethyl group.
- Sato, Kazuyuki,Inoue, Yuichi,Mori, Tomohisa,Sakaue, Atsushi,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
-
supporting information
p. 3756 - 3759
(2014/08/05)
-
- Straightforward synthesis of substituted dibenzyl derivatives
-
The C-C bond formation by homogeneous catalysis is a powerful tool in organic synthesis. The replacement of noble metal by cheaper one for already reported methodologies is of interest for an economical purpose. The attractivity of such replacement is also enhanced if a first raw transition metal is found to be active in several processes. This work demonstrates that a common nickel complex can be used for a two-step cross-coupling procedure, namely a homocoupling reaction of benzyl derivatives and a subsequent Suzuki reaction. These consecutive reactions permit the synthesis of new polyfunctionalized dibenzyl compounds.
- Mboyi, Clève D.,Gaillard, Sylvain,Mabaye, Mbaye D.,Pannetier, Nicolas,Renaud, Jean-Luc
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p. 4875 - 4882
(2013/06/26)
-
- Ultrasound-promoted dimerization of benzylic halides
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Simple and straightforward coupling of benzylic compounds was achieved by sonicating benzylic halides in the presence of magnesium.
- Gozhina, Olga V.,Thomassen, Ivar K.,Lejon, Tore
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p. 1867 - 1870
(2013/05/21)
-
- Iron nanoparticle-promoted Cu (I)-catalysed homocoupling of arylmethyl halides for the synthesis of 1,2-diarylethanes
-
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)
-
- Controlling chain conformation in conjugated polymers using defect inclusion strategies
-
The Horner method was used to synthesize random copolymers of poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) that incorporated different backbone-directing monomers. Single-molecule polarization absorption studies of these new polymer
- Bounos, Giannis,Ghosh, Subhadip,Lee, Albert K.,Plunkett, Kyle N.,Dubay, Kateri H.,Bolinger, Joshua C.,Zhang, Rui,Friesner, Richard A.,Nuckolls, Colin,Reichman, David R.,Barbara, Paul F.
-
supporting information; experimental part
p. 10155 - 10160
(2011/08/21)
-
- Synthesis of the active form of loxoprofen by using allylic substitutions in two steps
-
High regioselectivity for allylic substitution of the cyclopentenyl picolinate 5 with benzylcopper reagent was attained with ZnBr2, and the finding was applied to the p-BrC6H4CH2 reagent. The cyclopentene moiety in the product was reduced to the cyclopentane, and the p-BrC6H4 was converted to the "Cu"C6H4 for the second allylic substitution with picolinate 8 to furnish the title compound after oxidative cleavage of the resulting olefin moiety.
- Hyodo, Tomonori,Kiyotsuka, Yohei,Kobayashi, Yuichi
-
supporting information; experimental part
p. 1103 - 1106
(2009/07/25)
-
- Facile synthesis of bibenzyl by reductive homocoupling of benzyl halides in aqueous media
-
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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- 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.
-
-
- Novel radical alkylation of carboxylic imides
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Although alkylation is one of the most important and fundamental organic reactions, radical-mediated alkylations of carboxylic acid derivatives have not been well studied. The first successful radical alkylation of carboxylic imides is achieved by the add
- Kim, Sunggak,Lim, Chae Jo,Song, Changsik,Chung, Won-Jin
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p. 14306 - 14307
(2007/10/03)
-
- Radical-mediated synthesis of trifluoroethyl amines and trifluoromethyl ketones from alkyl iodides
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Radical reaction of alkyl iodides with trifluoromethyl phenylsulfonyl oxime ether 10 and hexamethylditin at 300 nm in benzene afforded the corresponding trifluoromethyl oxime ethers 11 in high yields, which were reduced into the 2,2,2-trifluoroethyl amines with lithium aluminium hydride. The trifluoroethyl amines could be converted into the corresponding trifluoromethyl ketones by treatment with NBS and DBU.
- Kim, Sunggak,Kavali, Rajesh
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p. 7189 - 7191
(2007/10/03)
-
- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
-
- Zeolite as a reagent and as a catalyst: Reduction and isomerization of alkenes by Ca Y
-
Depending on the number of Bronsted acid sites present, Ca Y can act either as a reagent and reduce stilbenes to 1,2-diarylethanes or act as a catalyst and isomerize cis-stilbenes to the more stable trans form; Lewis acid sites generated by the activation process yield radical cations from stilbenes but these do not yield any stable products.
- Pitchumani,Joy, Abraham,Prevost, Nicolette,Ramamurthy
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p. 127 - 128
(2007/10/03)
-
- Dehalogenation of organic halides by flash vacuum pyrolysis over magnesium: A versatile synthetic method
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Flash vacuum pyrolysis over magnesium at 600°C results in efficient dehalogenation of a variety of organic halides and provides a preparatively useful method for C-C bond formation and other reactions.
- Aitken, R. Alan,Hodgson, Philip K. G.,Oyewale, Adebayo O.,Morrison, John J.
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p. 1163 - 1164
(2007/10/03)
-
- Selective reduction of organic compounds with indium hydride reagents
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Three indium hydride reagents (LiInH4, LiPhInH3, and LiPh2InH2) were prepared and successfully used for the selective reduction of various organic compounds.
- Yamada, Masafumi,Tanaka, Koji,Araki, Shuki,Butsugan, Yasuo
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p. 3169 - 3172
(2007/10/02)
-
- A novel copper (I) mediated, symmetrical coupling procedure for alkyl, aryl, benzyl, and thiophenyl dihalides
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A comparative study of Li2CuCl4 vs. Li2CuCl2 mediated mono-coupling reactions of dihalide substrates with allylmagnesium bromide is reported. Higher yields were obtained with Li2CuCl3 and the following trends in halide reactivity were observed. Br > Cl for alkyl, aryl, and thiophenyl dihalides; and benzyl halide > phenyl halide. Utilizing these trends, a symmetrical coupling procedure for alkyl, aryl, benzyl, and thiophenyl dihalides, simply carried out by combining the dihalide with metallic magnesium and Li2CuCl4 is reported.
- Johnson,Johnson, David K.,Ciavarri,Ciavarri, Jeffrey P.,Ishmael,Ishmael, Faoud T.,Schillinger,Schillinger, Kurt J.,Van Geel,Van Geel, Thomas A. P.,Stratton,Stratton, Stephen M.
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p. 8565 - 8568
(2007/10/02)
-
- Generation of allyl- and benzyllithiums from the corresponding halides by the aid of lithium-tellurium exchange reactions
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A variety of allyl- and benzyllithiums were prepared by lithium-tellurium exchange reactions of allylic and benzylic tellurides generated in situ from the corresponding halides.The produced organolithiums were trapped successfully with electrophiles such as aldehydes, ketones, and trimethylchlorosilane.Benzyllithiums having an alkyl, alkoxy,fluoro, chloro, or cyano substituent(s) on their aromatic ring were generated efficiently in THF.Benzylic tellurides bearing a bromo or iodo substituent afforded a mixture of products under similar conditions arising from the competing lithium-halogen exchange and/or the displacement of the halogen atom with organolithiums used, but they were converted selectively to benzyllithiums in ether without affecting halogen substituents on the benzene ring.Several allyllithiums including dilithioisobutene were generated from allylic halides in a similar way via allylic tellurides.Wurtz-type coupling was negligible in any reactions examined. Key words: Tellurium; Lithium; Allyl; Benzyl; Halide
- Kanda, Takahiro,Kato, Shinzi,Sugino, Takushi,Kambe, Nobuaki,Sonoda, Noboru
-
-
- Homolytic displacement at saturated carbon in organocobaloximes: Part VI - Synthesis of benzyl sulphones
-
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)
-
- Homolytic Displacement at Saturated Carbon in Organocobalamines. Part 4
-
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)
-
- W(CO)6 Mediated C-S Bond Cleavage Reactions
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W(CO)6-mediated reactions of thioethers in refluxing chlorobenzene yielded mainly the corresponding dimers.Optically active thioethers give the respective racemic products.Mercaptans, on the other hand, predominantly afford the corresponding reduced products.A deuterium labeling experiments suggest that the SH group is the hydrogen source in the latter reduction reactions.A free-radical mechanism is suggested.
- Ng, Chi Tat,Wang, Xiaojun,Luh, Tien-Yau
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p. 2536 - 2539
(2007/10/02)
-
- Le composes d'insertion du graphite comme precurseurs de metaux finement divises I. Couplage d'halogenures benzyliques
-
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)
-
- N-NITRENES. II. INVESTIGATION OF THE MECHANISM OF DISSOCIATION OF DIBENZYLAMINONITRENE BY CHEMICALLY INDUCED POLARIZATION OF 1H NUCLEI. THE SPIN STATE OF DIBENZYLAMINONITRENE
-
The mechanism of the dissociation of dibenzylaminonitrene and p-bromodibenzylaminonitrene into molecular nitrogen and hydrocarbon products was studied.Dibenzylaminonitrene forms dibenzyl and o- and p-benzyltoluenes.In the presence of thiophenol significant amounts of toluene are formed.During dissociation p-bromodibenzylaminonitrene gives a mixture of symmetrical and unsymmetrical dibenzyls.In the presence of octanethiol only unsymmetrical p-bromodibenzyl is formed.The dissociation of dibenzylaminonitrene takes place by synchronous cleavage of the two C-N bonds and the formation of a pair of benzyl radicals.Dibenzylaminonitrene dissociates from the singlet electronic state.
- Savin, V. I.
-
-
- HOMOLYTIC DISPLACEMENT AT SATURATED CARBON CENTRE: SYNTHESIS OF BENZYLSULPHONES
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The reactions of benzyl cobaloximes with p-substitued benzene sulphonyl chlorides under photochemical conditions from benzyl sulphones by novel SH2 process.
- Gupta, B. D.,Kumar, Manoj,Das, Indira,Roy, M.
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p. 5773 - 5776
(2007/10/02)
-
- Identification of the Products of Solvolysis of N-Benzylpyridinium Cations in the Absence of Nucleophiles
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Mono-, tri-, and penta-cyclic N-benzylpyridinium tetrafluoroborates undergo tharmolysis in chlorobenzene as solvent to give products of benzylation both of the solvent and of the pyridine leaving group.Thermolysis alone, and in nitrobenzene as solvent, yielded mainly products of benzylation of the leaving group.The results support the previously postulated mechanism of unimolecular solvolysis of compounds of these types in non-polar solvents.
- Katritzky, Alan R.,Marson, Charles M.,Chen, Jen-Luan,Saczewski, Franciszek,King, Roy W.
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p. 1331 - 1336
(2007/10/02)
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- IRON PENTACARBONYL MEDIATED COUPLING OF BENZYL HALIDES TO KETONES UNDER MILD PHASE TRANSFER CONDITIONS.
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In a two-phase system (saturated aqueous calcium hydroxide, tetrabutylammonium sulfate, dichloromethane, iron pentacarbonyl) benzyl bromides are readily carbonylated to dibenzyl ketones ; α-α' dibromoorthoxylene yields the o-quinodimethane iron tricarbonyl cmplex 8.It is inferred that the reactions proceed through transient generation of the tetracarbonyl ferrate dianion.
- Tanguy, Guy,Weinberger, Bernd,Abbayes, Hevre des
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p. 5529 - 5532
(2007/10/02)
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- Highly Reactive Metallic Nickel: Reductive Homocoupling Reagent for Benzylic Mono- and Polyhalides
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Metallic nickel, prepared by the reduction of nickel halides with lithium in glyme using naphthalene as an electron carrier, was found to be a useful reagent for the homocoupling of benzylic mono- and polyhalides.Benzyl halides reacted with metallic nickel at room temperature to give the corresponding 1,2-diarylethanes in good to high yields and functional groups on the aromatic ring such as methoxy, chloro, bromo, nitro, cyano, and alkoxycarbonyl groups were not affected under the conditions employed.Benzylic monohalides (1-(chloromethyl)- or 2-(bromomethyl)naphthalene, chlorodiphenylmethane, and 9-bromofluorene) also underwent coupling reactions with metallic nickel at room temperature to give the corresponding ethane derivatives.On the other hand, benzylic di- and trihalides such as α,α-dibromotoluene and α,α,α-trichlorotoluene yielded mixtures of cis and trans isomers of substituted ethenes.The intermediate of the reaction, benzylnickel complex, was trapped with electron deficient olefins such as methyl acrylate and acrylonitrile.
- Inaba, Shin-ichi,Matsumoto, Hideyuki,Rieke, Reuben D.
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p. 2093 - 2098
(2007/10/02)
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- CATALYTIC PHASE TRANSFER CARBONYLATION OF BENZYL HALIDES WITH IRON PENTACARBONYL.
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Benzyl halides are readily carbonylated to arylacetic acids in a two-phase system (aqueous sodium hydroxide (1M), tetrabutylammonium sulfate ; organic phase (CH2Cl2 or C6H6 or C6H5CH3)), using a catalytic amount of the cheap, easy to handle iron pentacarbonyl under carbon monoxide atmosphere.
- Tanguy, Guy,Weinberger, Berndt,Abbayes, Herve des
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p. 4005 - 4008
(2007/10/02)
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- Micellar Systems as ''Supercages'' for Reactions of Geminate Radical Pairs. Magnetic Effects
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The photochemistry of dibenzyl ketone (DBK) and other molecules capable of producing benzyl radicals and substituted benzyl radicals has been investigated in micellar systems.The cage effect (percent of unscavengeable radical pairs produced by photolysis) was measured under a variety of conditions, and the results are compared with those obtained in homogeneous organic solvents.For example, parameters such as mean occupancy of ketone, detergent type and concentration, O2 concentration, additives, temperature, applied magnetic field, and pressure have been varied and investigated as to their influence on the magnitude of cage effect.In addition to modifying its environment, structural modification of the DBK by incorporation of 2H and 13C isotopes, hydrophobic groups, and heavy atoms was performed to investigate the impact of these variations on the cage effect in micellar systems.Isotopic substitution of 2H or 13C leads to results on both the quantum yields for reactions and on the percent cage that were consistent with expectations of magnetic isotope effects.Hydrophobic groups substituted in the 4-position of DBK were found to cause a substantial increase in the cage effect and yet retain the magnetic-field-dependent character found in the parent DBK.Incorporation of Br in the 4-position of DBK was found to enhance the cage effect but at the same time cause the cage effect to become magnetic field independent.Substitution of α-naphthyl for phenyl in DBK also produced magnetic-field-independent behavior, in addition to a dramatic decrease in the efficiency of photolysis.
- Turro, Nicholas J.,Weed, Gregory C.
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p. 1861 - 1868
(2007/10/02)
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- Temperature and Substituent Effects on Regioselectivity in the Insertion of Arylcarbene into Alcohols
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Photolysis of aryldiazomethanes in methanol, ethanol, and 2-propanol gave OH insertion products along with small amounts of CH insertion products at ambient temperature.However, the CH insertion products increased significantly at the expense of the ether as the temperature was lowered.The attempted sensitized decomposition of the diazomethane did not lead to an increase in the CH insertion products presumably because of a rapid singlet-triplet equilibrium.The key intermediate leading to the CH insertion is suggested to be ground-state triplet arylcarbene, based on the accumulated spectroscopic as well as chemical evidence for the intervention of the triplet arylcarbene in the low-temperature photolysis of aryldiazomethanes.Substituents on the phenyl ring also have an appreciable effect on the insertion selectivity.At room temperature, the OH/CH insertion selectivity increased with the electron-donating ability of the substituents.This is interpreted in terms of the substituent effect on the transition state of OH insertion, where there is a deficiency of electrons at the benzylic carbon atom, rather than on the stability of singlet carbene.At low temperature, both electron-donating and -withdrawing substituents facilitate OH insertion, indicating the change in substituents induces a concomitant change in the insertion mechanism, presumably due to decreasing nucleophilicity of carbene with increasing electron-withdrawing ability as well as decreasing proton-donor activity of alcohol with decreasing temperature.This may also reflect the effect of the substituent on the singlet-triplet energy gap.
- Tomioka, Hideo,Suzuki, Shinji,Izawa, Yasuji
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p. 3156 - 3162
(2007/10/02)
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- Flash Pyrolysis of Selenides. Syntheses of Bibenzyls, Olefins, and Related Compounds
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Pyrolyses of a series of selenides and diselenides were studied. Selenides and diselenides bound with an active methylene group like benzyl gave a variety of substituted bibenzyls and related ethane derivatives in high yields. Other diselenides were easily caused to cleave to give various aromatic and aliphatic olefins in good yields together with elemental selenium. Lepidopterene, paracyclophane, and benzocyclobutene were prepared by thermal cleavage of their corresponding phenylselenomethyl-substituted compounds as an application of the pyrolysis concerned.
- Higuchi, Hiroyuki,Otsubo, Tetsuo,Ogura, Fumio,Yamaguchi, Hachiro,Sakata, Yoshiteru,Misumi, Soichi
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p. 182 - 187
(2007/10/02)
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- NEW SYNTHETIC METHOD OF PARACYCLOPHANE, BENZOCYCLOBUTENE, AND LEPIDOPTRENE: PYROLYSIS OF ARYLMETHYL PHENYL SELENIDES
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The flash vacuum pyrolysis of benzyl phenyl selenides gave bibenzyls and diphenyl diselenide in excellent yields.This type of reaction was successfully applied to the synthesis of the title compounds.
- Higuchi, Hiroyuki,Sakata, Yoshiteru,Misumi, Soichi,Otsubo, Tetsuo,Ogura, Fumio,Yamaguchi, Hachiro
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p. 627 - 630
(2007/10/02)
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