- 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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p. 7810 - 7815
(2021/09/28)
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- Discovery and mechanistic investigation of Pt-catalyzed oxidative homocoupling of benzene with PhI(OAc)2
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We present a Pt-catalyzed direct coupling of benzene to biphenyl. This catalytic reaction employs a cyclometalated platinum(ii) complex [PtMe(bhq)(SMe2)] (bhq = benzo[h]quinolate) with PhI(OAc)2 as an oxidant and does not require an acid, a co-catalyst or a solvent. The reaction kinetics and characterization of potential catalytic species are reported. The reaction is first-order in Pt and second-order in benzene, which implicates the second C-H activation step as rate-determining. A Pt(ii)/Pt(iv) catalytic cycle is suggested. The reaction commences by oxidation of the Pt(ii) complex to give the platinum(iv) species [Pt(bhq)(SMe2)(OAc)2](OAc) followed by C-H activation of benzene to afford the intermediate [PtPh(bhq)(SMe2)(OAc)](OAc) concurrently with the release of HOAc. A second benzene molecule reacts similarly to give the diphenyl intermediate [PtPh2(bhq)(SMe2)](OAc). C-C bond forming reductive elimination ensues to regenerate Pt(ii) and complete the catalytic cycle. The proposed mechanism has been examined by DFT computations, which provide support to experimental findings.
- Abu-Omar, Mahdi M.,Nabavizadeh, S. Masoud,Niroomand Hosseini, Fatemeh,Park, Chan,Wu, Guang
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supporting information
p. 2477 - 2486
(2020/03/05)
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- Ni-Catalyzed Iterative Alkyl Transfer from Nitrogen Enabled by the in Situ Methylation of Tertiary Amines
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Current methods to achieve transition-metal-catalyzed alkyl carbon-nitrogen (C-N) bond cleavage require the preformation of ammonium, pyridinium, or sulfonamide derivatives from the corresponding alkyl amines. These activated substrates permit C-N bond cleavage, and their resultant intermediates can be intercepted to affect carbon-carbon bond-forming transforms. Here, we report the combination of in situ amine methylation and Ni-catalyzed benzalkyl C-N bond cleavage under reductive conditions. This method permits iterative alkyl group transfer from tertiary amines and demonstrates a deaminative strategy for the construction of Csp3-Csp3 bonds. We demonstrate PO(OMe)3 (trimethylphosphate) to be a Ni-compatible methylation reagent for the in situ conversion of trialkyl amines into tetraalkylammonium salts. Single, double, and triple benzalkyl group transfers can all be achieved from the appropriately substituted tertiary amines. Transformations developed herein proceed via recurring events: The in situ methylation of tertiary amines by PO(OMe)3, Ni-catalyzed C-N bond cleavage, and concurrent Csp3-Csp3 bond formation.
- Nwachukwu, Chideraa Iheanyi,McFadden, Timothy Patrick,Roberts, Andrew George
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p. 9979 - 9992
(2020/09/03)
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- Chemical Transformations of Tetracyclo[3.3.1.13,7.01,3]decane (1,3-Dehydroadamantane): IX. Noncatalytic Reactions with Alkylarenes
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Abstract: The reaction of 1,3-dehydroadamantane with alkylbenzenes was studied for the first time. It involved the C–H bond of the alkyl substituent in the α-position with respect to the aromatic ring. The proposed radical mechanism of the reaction was co
- Butov, G. M.,Mokhov, V. M.,Zubovich, E. A.
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p. 1041 - 1045
(2020/07/25)
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- 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)
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- Photoredox-Catalysis-Modulated, Nickel-Catalyzed Divergent Difunctionalization of Ethylene
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Divergent synthesis that enables a catalytic reaction to selectively produce different products from common substrates will allow the charting of wider chemical space and the unveiling of distinct mechanistic paradigms. A common strategy for it employs different ligands to modulate organometallic catalysts. Dramatic developments in photocatalysis have enabled previously inaccessible transformations. In particular, photoredox catalysis modulates the oxidation state of transition-metal complexes, offering enormous opportunities for methodology development. Herein, we developed a photo-mediated divergent ethylene difunctionalization via modulating oxidation states of the nickel catalyst by using different photoredox catalysts. This work will inspire new perspectives for value-added chemical synthesis using ethylene as a feedstock and shed light on photoredox-catalyst-based divergent synthesis, which fundamentally differs from ligand-controlled transition-metal catalysis.Divergent synthesis represents a powerful strategy for directly accessing different molecular scaffolds originating from the same starting materials. Access to different end products via transition-metal catalysis is conventionally achieved by ligand control. We herein demonstrate the use of ethylene feedstock and commercially available aryl halides to accomplish the divergent synthesis of 1,2-diarylethanes, 1,4-diarylbutanes, or 2,3-diarylbutanes in a highly selective fashion through the synergistic combination of nickel and photoredox catalysis. Mechanistic studies suggest that the observed selectivity was due to different active states of Ni(I) and Ni(0) modulated by Ru- and Ir-based photoredox catalysts, respectively. The ability to access different organometallic oxidation states via photoredox catalysis promises to inspire new perspectives for synergistic transition-metal-catalyzed divergent synthesis.Functionalization of ethylene without polymerization is challenging under photo-irradiation conditions. We have demonstrated that the photo-transformation of ethylene can be controllable by merging photoredox and transition-metal catalysis. In our study, the use of different photoredox catalysts was able to modulate the oxidation state of the nickel catalyst. Through different oxidation states, the nickel-catalyzed couplings proceeded via distinct pathways to generate divergent ethylene difunctionalization products selectively from the same feedstock.
- Li, Jiesheng,Luo, Yixin,Cheo, Han Wen,Lan, Yu,Wu, Jie
-
supporting information
p. 192 - 203
(2019/01/21)
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- Method for synthesizing 1,2-diphenylethane derivative by catalyzing coupling of sp3C-H bond through graphene-loaded palladium/platinum
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The invention provides a novel method for catalyzing activation of an sp3C-H bond to build a 1,2-diphenylethane compound by developing a novel graphene-loaded bimetal palladium/platinum catalyst whichis simple, convenient and efficient, is free of guide groups and free of participation of solvents and can be reused, so as to increase the yield of the target product, simplify operation steps and improve an atom utilization ratio and the recovery of the catalyst. The invention provides an economical, efficient and green method for preparing the compound. The method has the main advantages thatexperiment operation is simple and convenient, guide groups are not needed, the participation of other solvents is not needed, and the catalyst can be repeatedly recycled.
- -
-
Paragraph 0031; 0032
(2018/07/15)
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- Nondirecting Group sp3 C?H Activation for Synthesis of Bibenzyls via Homo-coupling as Catalyzed by Reduced Graphene Oxide Supported PtPd@Pt Porous Nanospheres
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The use of heterogeneous bimetallic Pd-based nanocatalyst for directing the inactivated sp3 C?H coupling has been scarcely explored. This work reported the formation of symmetrical C?C bonds from the inactivated sp3 C?H bonds catalyzed by employing reduced graphene oxide supported PtPd@Pt porous nanospheres. The reaction of sp3 C?H activation proceeded under mild conditions without any solvent, ligand or directing group. It is a higher atom-, step- and cost-effectiveness strategy for developing heterogeneous catalysts in the synthesis of bibenzyls with various functional groups (e. g. aryl, alkyl, methoxyl, halogen, ester, and pyridyl). (Figure presented.).
- Wang, Zheng-Jun,Lv, Jing-Jing,Yi, Rong-Nan,Xiao, Min,Feng, Jiu-Ju,Liang, Zhi-Wu,Wang, Ai-Jun,Xu, Xinhua
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supporting information
p. 932 - 941
(2018/01/05)
-
- An unprecedented oxidative intermolecular homo coupling reaction between two sp3C–sp3C centers under metal-free condition
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An unprecedented formation of benzylic sp3C–sp3C coupled dibenzylic products has been illustrated. The reactions have been carried out in the presence of three oxidizing reagents, i.e., diacetoxy-iodobenzene (IBDA), N-fluorobenzenesulfonimide (NFSI), and pyridine (Py) using toluene derivatives.
- Sahoo, Santosh K.
-
supporting information
p. 3476 - 3480
(2016/07/15)
-
- General Ambient Temperature Benzylic Metalations Using Mixed-Metal Li/K-TMP Amide
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Highly regioselective benzylic metalations in hydrocarbon solvent have been achieved at rt and 0 °C using a mixed-metal Li/K-TMP amide comprised of KOtBu, BuLi, and 2,2,6,6,-tetramethylpiperidine (TMP(H)). Mixing of KOtBu, BuLi, and TMP(H) in heptane gave a solution of the base mixture which when used in deuterium labeling experiments confirmed the requirement of the three reagent components for both reactivity and selectivity. The reaction protocol is operationally straightforward and found to be applicable to a broad range of substrates. Upon generation of the metalated products, they are reacted in heptane at ambient temperature in a variety of synthetically useful ways. Illustrated examples include generation of the benzyltrimethylsilanes and α,α-bis(trimethylsilyl)toluenes reagents, which are bench-stable surrogates of benzyl anions and α-silyl carbanions utilized for nucleophilic addition and Peterson olefination reactions. Direct C-C couplings mediated by 1,2-dibromoethane provided entries into bibenzyls and [2.2]metacyclophanes. Comparison of reaction outcomes with the same reactions carried out in THF at -78 °C showed no negative effects for conducting the reactions under these milder more user-friendly conditions.
- Manvar, Atul,Fleming, Patricia,O'Shea, Donal F.
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p. 8727 - 8738
(2015/09/15)
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- Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes
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A new two-step general approach to [2.2]metacyclophane synthesis from substituted m-xylenes is described. The strategy employs a selective benzylic metalation and oxidative C-C bond formation for both synthetic operations. Regioselective benzylic metalati
- Blangetti, Marco,Fleming, Patricia,O'Shea, Donal F.
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supporting information; experimental part
p. 1249 - 1254
(2011/11/05)
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- Cation-π interactions in the gas phase methylation of α,ωdiphenylalkanes
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The methylation of α,ω-diphenylalkanes (C6H5(CH2)nC6H5 , n = 1-6) has been performed in the gas phase using Me2Cl+ ions as alkylating species and toluene as reference substrate. Both in radiolytic experiments at atmospheric pressure and in FT-ICR measurements at 10-8 Torr, the selected diphenylalkanes reacted faster than toluene, the highest reactivity displayed by 1,3-diphenylpropane. The kinetic pattern of the reaction, conforming to the established scheme of an electrophilic alkylation reaction, is consistent with a rate-determining formation of the σ-complex intermediate, at variance with the tert-butylation of the same series of compounds by Me3C+ ions, occurring at the collisional encounter rate. The kinetic features are explained by a marked effect due to the presence of the second aryl ring, providing additional stabilization of both the ion-neutral collision complex and the σ complex with respect to toluene. Both factors contribute to the δEa of ca. 8 kcal mol-1 for the competition of 1,3-diphenylpropane and toluene found in the temperature dependence study of the Me2Cl+ reaction.
- Chiavarino, Barbara,Crestoni, Maria E.,Fornarini, Simonetta,Kuck, Dietmar
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p. 4619 - 4624
(2007/10/03)
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- Photodecarboxylation of arylacetic acids induced by light-sensitive Hg2F2
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Photolysis of arylacetic acids in argon-saturated acetonitrile in the presence of Hg2F2 gives the corresponding 1,2-diarylethanes as the major product via a radical pathway. This reaction offers an interesting procedure for selective decarboxylation of arylacetic acids with the assistance of a light-sensitive compound.
- Habibi, Mohammad H.,Farhadi, Saeid
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p. 2821 - 2824
(2007/10/03)
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- Mechanism of the Solution-Phase Reaction of Alkyl Sulfides Atomic Hydrogen. Reduction via a 9-S-3 Radical Intermediate
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The low selectivity of benzyl alkyl sulfide fragmentation subsequent to its reaction with atomic hydrogen is indicative of a reaction that proceeds via an early transition state. The competitive reduction of a series of substituted-benzyl alkyl sulfides was insensitive to the substituent on the aromatic ring (ρ = -0.13, r = 0.99). The relative rates of fragmentation of a series of the substituted-benzyl alkyl sulfides gave a V-shaped Hammett plot. Both electron-donating and electron-withdrawing groups destabilized the transition state (ρ = +0.99, r = 0.999; ρ = -0.82, r = 0.992). Since the relative rates of disappearance of the alkyl benzyl sulfides are not substituent dependent, but the relative rates of fragmentation are, a 9-S-3 intermediate is preferred as the structure leading to products.
- Tanner, Dennis D.,Koppula, Sudha,Kandanarachchi, Pramod
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p. 4210 - 4215
(2007/10/03)
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- 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)
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- Mechanistic and synthetic aspects of a novel route to poly-p-xylylene (PPX) via nickel complex catalysed electropolymerisation of 1,4-bis(chloromethyl)benzene
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It is shown that in the presence of catalytic amounts of NiIICl2L2 (L2 = dppe or dppp) 1,4-bis(chloromethyl)benzene is electrochemically reduced to poly-p-xylylene (PPX). Cyclic voltammetric examination of this reaction, and of the analogous conversion of benzyl chloride into bibenzyl, is combined with the construction of reactant/product vs. charge profiles to develop a detailed mechanistic description. There is compelling evidence that, in contrast with the established cathodic formation of PPX from 1,4-bis(halomethyl)benzene via electrogenerated quinodimethane (xylylene), the Ni complex catalysed route involves oxidative addition of the halide derivative to Ni0L2.
- Amatore, Christian,Gaubert, Florence,Jutand, Anny,Utley, James H. P.
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p. 2447 - 2452
(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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- A Superior Procedure for Generation of Substituted Benzyllithiums from the Corresponding Chlorides
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The use of diethyl ether-tetrahydrofuran-light petroleum (b.p. 30-40 deg C) (4:3:1) as solvent for the reaction of substituted benzyl chlorides with lithium naphthalenide at low temperature gives useful yields of the corresponding benzyllithium compounds, which react with electrophiles such as iodomethane and water to yield the expected reaction products.
- Smith, Keith,Hou, Daunjie
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p. 185 - 186
(2007/10/02)
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- The Photochemistry of Methoxy-Substituted Benzyl Acetates and Benzyl Pivalates: Homolytic vs Heterolytic Cleavage
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The multiple methoxy-substituted benzyl acetates (3g-i) and benzyl pivalates (4g-i) have been photolyzed in methanol solution.The products of these reactions are derived from two critical intermediates; the benzyl radical/acyloxy radical pair and the benzyl cation/carboxylate anion pair.As predicted by the meta effect, the yield of ion-derived product, the methyl ether in this case, was enhanced by the presence of the m-methoxy groups.The yield of ether, for the acetate esters, varied from 2percent for the 4-methoxy-substituted ester to 66percent for the 3,4,5-trimethoxy-substituted ester.In contrast, the yield of ether, for the pivalate esters, varied from 1percent for the 4-methoxy-substituted ester to 20percent for the 3,4,5-trimethoxy-substituted one.The meta effect does not explain these differences; electron transfer converting the radical pair to the ion pair is still an important pathway in the mechanism for ion formation.A quantitative analysis of the yield of the ethers was done in order to obtain the electron-transfer rate constants.This analysis revealed that the yield of the ethers was higher than expected based on previous results for other substituted benzyl acetates.A possible explanation for this discrepancy is that internal return of the radical pair to starting material for the acetate esters is more efficient than for the pivalate esters.Also, the esters 3k and 3l, were prepared to study the effect of electron-withdrawing groups in the meta position.For these esters, the benzylic cleavage reactions were inefficient and an isomerization reaction, the benzvalene rearrangement, was competitive.
- Pincock, J. A.,Wedge, P. J.
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p. 5587 - 5595
(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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- Unusual selective α-fission of indium-sec-alkyl bonds in solution
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Indium trialkyls possessing an α-branch such as In(Bu-s)3 and In(Pr-i)3 decompose through a-fission to give the corresponding alkyl radical selectively during solution pyrolysis.
- Nomura, Ry?ki,Miyazaki, Shin-Ichiro,Matsuda, Haruo
-
-
- Samarium(II) Diiodide Mediated Coupling of Bis(bromomethyl)arenes. Facile Synthesis of n>Cyclophanes without using High-Dilution Techniques
-
In the presence of samarium(II) diiodide (Sml2), coupling of 1,3- and 1,4-bis(bromomethyl)benzenes proceeds smoothly to give their cyclic and acyclic oligomers.Use of 1.2 equiv. of Sml2 gives 1,2-bis(3- and 4-bromomethylphenyl)ethanes, respectively, in 95percent yield, and the use of 5.0 equiv. of Sml2 affords n>metacyclophanes and n>paracyclpphanes (n = 2, 3 and 4), respectively, in satisfactory yields.By using 5.0 equiv. of Sml2, 2-bromo- and 2-methoxy-1,4-bis(bromomethyl)benzenes and 1,4- and 2,6-bis(bromomethyl)naphthalenes each give only one of several expected isomeric cyclophanes as the major cyclic oligomer.
- Takahashi, Senji,Mori, Nobuo
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p. 2029 - 2032
(2007/10/02)
-
- High-Temperature Oxidation Mechanisms of m- and p-Xylene
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Mechanisms for the oxidation of m- and p-xylene were developed with the aid of atmospheric flow reactor tests at temperatures ranging from 1093 to 1199 K and equivalence ratios from 0.47 to 1.7.The experimental data suggested that m-xylene is oxidized by sequential oxidation and removal of the methyl side chains while p-xylene reacts through simultaneous, as well as sequential, oxidation of the side chains.The formation of p-xylylene (3,6-bis(methylene)-1,4-cyclohexadiene), postulated to occur during the oxidation of p-xylene, opens up the simultaneous oxidation route and leads to the formation of p-phthalaldehyde.The formation of m-xylylene during the oxidation of m-xylene was determined to be unfavorable.In order to better understand specific steps of the mechanisms, the oxidation of p-tolualdehyde and the pyrolysis of p-methylanisole were also studied. p-Tolualdehyde tests were used to show that the aldehydic side chain is consumed quicker than the methyl side chain.Because p-methylanisole decays quickly to methyl and p-methylphenoxy radical, it was used to determine the fate of methylphenoxy radical formed during the xylene tests.The results indicated that methylcyclopentadienyl and CO are formed from the methylphenoxy and that methylcyclopentadienyl rearranges quickly to benzene and hydrogen atom.
- Emdee, J. L.,Brezinsky, K.,Glassman, I.
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p. 1626 - 1635
(2007/10/02)
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- Photochemistry of phosphate esters: An efficient method for the generation of electrophiles
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The photochemical cleavage of benzyl diethyl phosphates, 1a-g, has been examined in tert-butyl alcohol, which produces the corresponding benzyl tert-butyl ether as the major solvolysis product upon direct irradiation. The multiplicity of the reactive excited state has been established as the singlet state. Evidence favoring an intermediate benzyl cation-phosphate ion pair formed from photofragmentation includes oxygen-18 scrambling, racemization of chiral benzyl phosphates, and substituent effects on the rate of reaction. The existence of an electrophilic intermediate is further supported by a linear free energy relationship for the rate of disappearance of 1, kdis, with Hammett σ, which gave a ρ value of -0.90 and for the rate of appearance of 2, kapp, a Hammett ρ value of -0.97. Possible mechanisms including an electron transfer either before or after homolysis or simple heterolysis of the ester bond are evaluated.
- Givens, Richard S.,Matuszewski, Bogdan,Athey, Phillip S.,Robert Stoner
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p. 6016 - 6021
(2007/10/02)
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- A simple synthetic method of cyclophanes by Lanthanoid-mediated coupling of bis(bromomethyl)benzenes
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The coupling of bis(bromomethyl)benzenes with iodized samarium, cerium or misch metal gives cyclophanes in satisfactory yields in a short time.
- Takahashi, Senji,Mori, Nobuo
-
-
- A novel synthesis of aromatic α-diketones from electron transfer reactions of aromatic acids with either lithium 4,4'-di-t-butylbiphenyl radical anion or lithium metal
-
Some aromatic α-diketones were directly synthesized in high yields from ultrasound-promoted reactions of the corresponding acids with excess lithium in dry THF. Use of a catalytic amount of 4,4'-di-t-butylphenyl (DBB) enhanced the coupling reaction rate.
- Karaman,Fry
-
p. 6267 - 6270
(2007/10/02)
-
- CYANOETHYLATION OF HYDROCARBONS, INITIATED BY AUTOOXIDATION
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Oxygen was used as an initiator of the free-radical cyanoethylation of alkylbenzenes (toluene, o-, m-, and p-xylenes, mesitylene, ethylbenzene, p-cymene) and tetralin (0.25-0.66 liter of oxygen to 1 liter of the hydrocarbon) The reactions were carried out in an autoclave at 150-350 deg C with a carbon-acrylonitrile ratio of 100:1.The initiation evidently results mainly from homolytic dissociation of the hydroperoxide formed during the autooxidation of the hydrocarbons.The effectiveness of oxygen for the initiation of the cyanoethylation of hydrocarbons depends on the oxidizability of the hydrocarbons.
- Galust'yan, G. G.
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p. 811 - 815
(2007/10/02)
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- Photochemical Oxidation of Toluene and Xylenes. Concurrent Formation of Products Due To Photooxygenation and Photodimerization
-
Irradiation throuh pyrex of toluene and o-, m- and p-xylene in the liquid phase in the presence of air gave product mixtures which mainly contained alcohols, aldehydes, acids, and various dimers.
- Sydnes, Leiv K.,Burkov, Ivan C.,Hansen,Sissel H.
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p. 829 - 836
(2007/10/02)
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- REARRANGEMENT OF RADICALS IN THE HOMOLYTIC ADDITION OF m-XYLENE TO METHYL METHACRYLATE
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Investigation of the products from the reaction of m-xylene with methyl methacrylate under the conditions of thermal and peroxide initiation led to the isolation and identification of compounds which indicated that rearrangement of the intermediate radical-adducts occured in addition to the main process.The rearrangement takes place mainly with 1,5-H migration, but 1,3-H migration also takes place at high temperatures (350 deg C).
- Galust'yan, G. G.
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p. 1065 - 1067
(2007/10/02)
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- CATALYTIC PHASE TRANSFER CARBONYLATION OF BENZYL HALIDES WITH IRON PENTACARBONYL.
-
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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- Chemistry of the tert-Butyl Radical: Polar Character, ρ Value for Reaction with Toluenes, and the Effect of Radical Polarity on the Ration of Benzylic Hydrogen Abstraction to Addition to Aromatic Rings
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We have reexamined the reactions of tert-butyl radicals with toluenes and have obtained a ρ value of 0.49 +/- 0.04 at 80 deg C.The new, independent system involves the quantification of all of the principal products from the reaction of tert-butyl radicals with mixtures of toluene and substituted toluene.Five major products contain benzyl fragments and are formed in significant yields: two symmetrical bibenzyls, the cross bibenzyl, and the two neopentylbenzenes that result from combination of tert-butyl and the two benzyl radicals.Attack on the side chain is a major reaction of free tert-butyl radicals and is the only significant reaction that they undergo other than cage and termination reactions. tert-Butyl radicals do not add to the ring of toluenes.Data on the relative rates of addition to benzenes and hydrogen abstraction from toluenes are collected for a series of radicals including hydrogen atoms; methyl, isopropyl, and tert-butyl radicals; and p-nitrophenyl, p-bromophenyl, and phenyl radicals.The data demonstrate that more electrophilic radicals have a larger tendency to add to rings whereas more nucleophilic radicals have a larger tendency to abstract benzylic hydrogens.
- Pryor, William A.,Tang, Felicia Y.,Tang, Robert H.,Church, Daniel F.
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p. 2885 - 2891
(2007/10/02)
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- Photoinduced Decomposition of Peracetic Acid in Xylenes. Orientation in Aromatic Substitution of Methyl and Hydroxyl Radicals
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The photolysis of peracetic acid (1) in o-,m- or p-xylenes (2) has been carried out using 2537-Angstroem or >2900-Angstroem light at 20-22 deg C.The yields of ethyltoluenes (3), trimethylbenzenes (4), and dimethylphenols (6) are higher at 2537-Angstroem than those at >2900-Angstroem photolysis, but the reverse is true with the yield of methylbenzyl alcohol (5).The isomer distribution of trimethylbenzenes (4) formed from o- (2a) or m-xylene (2b) suggests that an attack of methyl radical at the position meta to the methyl group is favored with 2537-Angstroem light, while an attack at the ortho position is preferential with >2900-Angstroem light.On the other hand, the isomer distribution of dimethylphenols (6) at 2537 Angstroem suggests that an attack of hydroxyl radical is favored at positions ortho and para to the methyl group.These orientations of radical attack are briefly discussed.
- Ogata, Yoshiro,Tomizawa, Kohtaro
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p. 785 - 788
(2007/10/02)
-