- O-alkylation of N-phenylhydroxylamine in dimethyl sulfoxide with methylarenesulfonates
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The methylation of N-phenylhydroxylamine (NPHA) with methylarenesulfonates in DMSO gives alkylation of the O atom in contrast to methylation in methanol where N alkylation occurs. The Hammett p values indicate that alkylations with N-methylanilines and NPHAs both involve the N atom. The NPHAs show "nominal α-effects" but involve comparison of N atoms with O atoms. The reactivity of the principle component, the zwitterion I, is examined with leaving group studies and comparison with benzyl alkoxide reactivity.
- Fountain,White, Robert D.,Patel, Kamlesh D.,New, Dallas G.,Xu, YuBo,Cassely, Aaron J.
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Read Online
- Cobalt-Catalysed Reductive Etherification Using Phosphine Oxide Promoters under Hydroformylation Conditions
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A phosphine-oxide-promoted, cobalt-catalysed reductive etherification using syngas as a reductant is reported. This novel methodology was successfully used to prepare a broad range of unsymmetrical ethers from various aldehydes and alcohols containing diverse functional groups, and was scaled-up to multigram scale under comparably mild conditions. Mechanistic experiments support an acetalization–hydrogenation sequence.
- Beller, Matthias,Delolo, Fábio G.,Fessler, Johannes,Gusevskaya, Elena V.,Junge, Kathrin,Neumann, Helfried,dos Santos, Eduardo N.
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supporting information
(2022/02/19)
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- Co2(CO)8-catalyzed reactions of acetals or lactones with hydrosilanes and carbon monoxide. A new access to the preparation of 1,2-diol derivatives through siloxymethylation
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The Co2(CO)8-catalyzed reaction of acetals with hydrosilanes and CO under mild reaction conditions (an ambient temperature under an ambient CO pressure), leading to the production of vicinal diols is reported. A siloxymethyl group can be introduced via the cleavage of one of two alkoxy groups in the acetal. The effects of the types of hydrosilanes, acetals, solvents, and reaction temperatures on the yield of siloxymethylation products were examined in detail. The reactivity for hydrosilanes is as follows; HSiMe3 > HSiEtMe2 > HSiEt2Me > HSiEt3. Hemiacetal esters are more reactive than dimethyl acetals. The polarity of the solvent used also has a significant effect on both the course of the reaction as well as the reaction rate. The site-selective siloxymethylation can be achieved in the case of cyclic acetals such as tetrahydrofuran (THF) and tetrahydropyrane (THP) derivatives, depending on the nature of the oxygen substituent attached adjacent to the oxygen atom in the ring. When 2-alkoxy THF or THP derivatives are used as substrates, the siloxymethylation takes place with cleavage of the ring C-O bond. In contrast, the reaction of 2-acetoxy THF or THP derivatives results in siloxymethylation with the cleavage of C-OAc bond. The ring-opening siloxymethylation of lactones was also examined.
- Chatani, Naoto,Fujii, Satoru,Kido, Yoichi,Nakayama, Yasuhide,Kajikawa, Yasuteru,Tokuhisa, Hideo,Fukumoto, Yoshiya,Murai, Shinji
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- Visible light mediated oxidation of benzylic sp3 C-H bonds using catalytic 1,4-hydroquinone, or its biorenewable glucoside, arbutin, as a pre-oxidant
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Benzylic ethers undergo a visible light induced C-H activation and oxygen insertion to give the corresponding benzoate esters in moderate to good yields. The conditions employ substoichiometric amounts of 1,4-hydroquinone with copper(ii) chloride dihydrate as an electron-transfer mediator, oxygen as the terminal oxidant and dimethyl carbonate as solvent under visible light irradiation. The naturally occurring glucoside, arbutin, which is commercially available or can be accessed via extraction of the leaves of bearberry (Arctostaphylos uva-ursi) or elephant ears (Bergenia crassifolia) can be used as a biorenewable source of 1,4-hydroquinone. The methodology exploits the increase in oxidizing ability of quinones upon irradiation with visible light, and offers a sustainable alternative for the late stage oxidative functionalization of benzylic C-H bonds. It is applicable to a range of cyclic benzylic ethers such as isochromans and phthalans, and simple benzyl alkyl ethers. It can also be applied in the oxidation of benzylic amines into amides, and of diarylmethanes into the corresponding ketones. Mechanistic studies suggest that the reaction proceeds by H-abstraction by the photo-excited triplet benzoquinone to give a benzylic radical that subsequently reacts with molecular oxygen.
- Finney, Laura C.,Mitchell, Lorna J.,Moody, Christopher J.
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supporting information
p. 2242 - 2249
(2018/05/28)
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- Methoxymethylation and benzyloxymethylation of aryl bromides
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The methoxymethylation and benzyloxymethylation of aryl bromides methodology was reported here. The transition metal free, high yielding one pot procedure will be useful for synthetic community.
- Panda, Biswajit
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p. 981 - 985
(2020/06/26)
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- Auto-Tandem Catalysis with Frustrated Lewis Pairs for Reductive Etherification of Aldehydes and Ketones
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Herein we report that a single frustrated Lewis pair (FLP) catalyst can promote the reductive etherification of aldehydes and ketones. The reaction does not require an exogenous acid catalyst, but the combined action of FLP on H2, R-OH or H2O generates the required Br?nsted acid in a reversible, “turn on” manner. The method is not only a complementary metal-free reductive etherification, but also a niche procedure for ethers that would be either synthetically inconvenient or even intractable to access by alternative synthetic protocols.
- Bakos, Mária,Gy?m?re, ádám,Domján, Attila,Soós, Tibor
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supporting information
p. 5217 - 5221
(2017/04/27)
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- Selective O-methylation of phenols and benzyl alcohols in simple pyridinium based ionic liquids
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Synthesis of pyridinium based ionic liquids were reported and applied as catalyst for the selective O-methylation of phenols and benzyl alcohols. The reactions were carried out by using dimethylcarbonate (DMC) as the methylating agent. High selectivity, high yield and recyclability of the ionic liquids are important features of the reactions.
- Das, Pranab Jyoti,Das, Jupitara
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- Eco-efficient preparation of a N-doped graphene equivalent and its application to metal free selective oxidation reaction
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Here, we demonstrate that graphene oxide (GO) can be converted to N-doped reduced GO (rGO) that could become a substitute for N-doped graphene. Simultaneous doping and reduction can be accomplished for this purpose by simply mixing GO with hydrazine and then continuously sonicating the solution at 65 °C. A high level of reduction is realized, as evidenced by a carbon to oxygen ratio of 20.7 that compares with the highest value of 15.3 ever reported in solution (water + hydrazine) methods. Nitrogen doping is possible up to 6.3 wt% and the extent of doping can be increased with increasing sonication time. Notably, the simple tuning process of N-doping in GO greatly enhanced the efficiency of the carbocatalyst for various kinds of metal free oxidation reactions and hence is proposed as a suitable candidate for future industrial applications. This journal is the Partner Organisations 2014.
- Singh, Ajay K.,Basavaraju,Sharma, Siddharth,Jang, Seungwook,Park, Chan Pil,Kim, Dong-Pyo
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supporting information
p. 3024 - 3030
(2014/06/10)
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- Reductive etherification of aldehydes photocatalyzed by dicarbonyl pentamethylcyclopentadienyl iron complexes
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The reductive etherification of aldehydes can be performed by the reaction with dialkylmethylsilanes in the presence of new iron(II) piano-stool catalysts of general formula Cp*Fe(CO)2Ar (Cp * = η5-C5Me5; Ar = Ph, 4-C6H4OCH3, 4-C6H4CH 3, Fc). This transformation is promoted by UV light and affords a simple route for the preparation of unsymmetrical alkyl ethers.
- Argouarch, Gilles,Grelaud, Guillaume,Roisnel, Thierry,Humphrey, Mark G.,Paul, Frédéric
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supporting information
p. 5015 - 5018
(2012/11/07)
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- New method for the synthesis of benzyl alkyl ethers mediated by FeSO 4
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The synthesis of benzyl alkyl ethers from benzyl bromides and alcohols using FeSO4 as a recoverable and reusable mediator has been described without use of base and cosolvent under mild conditions.
- Joshi, Girdhar,Adimurthy, Subbarayappa
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experimental part
p. 720 - 728
(2011/03/22)
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- COST EFFECTIVE METHOD FOR SYNTHESIS OF TRIARYLAMINE COMPOUNDS
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A process for forming a triarylamine compound includes reacting a halogenated aryl alcohol with an alcohol protecting agent and a first base to form a halogenated protected aryl alcohol compound, and reacting the halogenated protected aryl alcohol compoun
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Page/Page column 10
(2008/12/04)
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- A kinetic model for water reactivity (avoiding activities) for hydrolyses in aqueous mixtures - Selectivities for solvolyses of 4-substituted benzyl derivatives in alcohol-water mixtures
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For solvolyses of various benzyl substrates in ethanol-water (EW) and methanol-water (MW) mixtures, product selectivities (S) are reported for chlorides at 75°C defined as follows using molar concentrations: S= ([ether product]/[alcohol product]) × ([water]/[alcohol solvent]). The results support earlier evidence that solvolyses of 4-nitrobenzyl substrates are S N2 processes, which are not susceptible to mechanistic changes over the whole range of solvents from water to alcohol. S values at 25 and/or 45°C in EW and MW, and additional kinetic data including kinetic solvent isotope effects (KSIE) are reported for solvolyses of 4-nitrobenzyl mesylate and tosylate. A kinetic model, explaining both rates and product, is proposed; a general medium effect due to solvent polarity is combined in one parameter with solvent effects on the nucleophilicity of the water and alcohol molecules acting as nucleophiles in SN2 reactions. According to this model, as alcohol is added to water the rate of reaction decreases due to a decrease in solvent polarity, but the nucleophilicity of water increases relative to alcohol. The availability of experimental rate and product data over the whole range of solvent compositions from alcohol to water, reveals limitations of alternative approaches using activities. Copyright
- Bentley, T. William,Koo, In Sun,Choi, Hojune,Llewellyn, Gareth
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p. 251 - 256
(2008/09/20)
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- Iodine catalyzed selective O-alkylation of alcohols with orthoesters
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In the present communication O-alkylation of a number of allylic and benzylic alcohols has been described.
- Kumar,Anjaneyulu,Joyasawal, Sipak,Pawan Chakravarthy,Naveen Kumar,Yadav
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p. 189 - 192
(2008/02/13)
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- Redox reaction of benzyl radicals with aromatic radical ions photogenerated. The Marcus inverted region and the selective formation of carbocations or carbanions
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Efficient redox reactions of benzyl-type radicals were achieved by irradiating an aromatic donor/acceptor pair with substituted dibenzyl ketones as a radical precursor in MeOH-MeCN. In this system, the aromatic radical ion pair was generated by photoinduced electron transfer followed by one-electron oxidation and reduction of photogenerated benzyl radicals (R·) by the radical ions to afford benzyl cations (R+) and anions (R-). The cations and anions were trapped by MeOH to yield ROMe and RH, respectively. The relative product ratios were determined for a variety of donor-acceptor pairs, reflecting the relative efficiencies of the redox reaction of benzyl radicals with a steady-state concentration of radical ions. The selective formation of carbocations or carbanions was achieved in some sets of donor/acceptor pairs. Assuming that the radical ions exist in a 1:1 ratio in the steady state, the product ratios are equal to the relative electron transfer rates, which are analyzed in terms of the free energy changes of the processes. The present results indicated that the rates became maximal at the energy gap of ca. -0.5 eV, representing a novel example of the Marcus inverted region. This interpretation is discussed in comparison with other related cases and in relation to recent theories on electron transfer rates.
- Ishiguro, Katsuya,Nakano, Tomoharu,Shibata, Hiroki,Sawaki, Yasuhiko
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p. 7255 - 7264
(2007/10/03)
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- The Mechanism of RuO4-Mediated Oxidations of Ethers: Isotope Effects, Solvent Effects and Substituent Effects
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The mechanism of the RuO4-mediated oxidation of ethers to esters has been investigated.Oxidation of cyclopropylmethyl methyl ether gave methyl cyclopropanecarboxylate.No rearranged products were observed.On RuO4 oxidation of benzyl methyl ether and p-methoxybenzyl methyl ether in CCl4 with NaIO4 as stoichiometric oxidant, no chlorinated products were observed.A series of 4-substituted benzyl methyl ethers was oxidized with RuO4-NaIO4.A correlation of the rate of the reaction with Hammett ?-values gave a ρ of -1.7, indicating only a moderate charge separation in the transition state (TS).Benzyl methyl ether (1) was oxidized in a series of acetone-water mixtures.From these experiments, a Grunwald-Winstein m-value of 0.11 was obtained, indicating a non-polar TS for the reaction.PhCHDOCH3 (2) and PhCD2OCH3 (3) were oxidized and two deuterium isotipe effects, one of 6.1+/-0.4 and another of 1.3+/-0.1 were obtained.If one assumes a one-step reaction mechanism, the value of 1.3 would be a large α-secondary isotope effect, indicating a change in the hybridization of the benzylic carbon during the reaction. α-Methylbenzyl methyl ether (4) was oxidized at a seventh of the rate of 1, despite the fact that 4 would have given a more stable carbocation than 1.These conflicting pieces of evidence are difficult to rationalise with a hydride or hydrogen abstraction mechanism.Instead it is proposed that the reaction proceeds by either a concerted reaction or by a reversible oxidative addition of the ether to RuO4 followed by a slow concerted step to give the product.
- Bakke, Jan M.,Froehaug, Astrid E.
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p. 615 - 622
(2007/10/02)
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- Photolysis of (Arylmethyl)triphenylphosphonium Salts. Substituent, Counterion, and Solvent Effects on Reaction Products
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Quaternary (arylmethyl)phosphonium salts of the general formula ArCH2-PR3(+)Y(-) (Ar = substituted phenyl or 1-naphthyl; R = phenyl, ferrocenyl, or butyl; Y(-) = BF4(-) or halide) have been photolyzed in acetonitrile or in methanol.Photolysis involved the cleavage of the P-CH2 bond and the products derived from both, the arylmethyl radical and the carbocation, were formed.The proportion of the radical- and carbocation-derived products was determined as a function of substituents in group Ar, of groups R, counterions Y(-), and the solvent.For the nonoxidizable counterion (BF4(-), the proposed mechanism of the reaction involves initial homolysis, followed by the escape of the radical products from a solvent cage, or by the electron transfer from carbon to phosphorus, yielding the corresponding arylmethyl carbocation.The latter can either react with the solvent to form the observed carbocation-derived product or can undergo recombination with the tertiary phosphine formed to yield the starting phosphonium ion.Some indication of the "inverted substituent effect" resulting from the inhibition of single electron transfer from an easily oxidized radical was obtained.For the oxidizable counterions (halides), an additional pathway is suggested, that involves electron transfer from the anion, yielding the arylmethyl radical and the phosphine, thus decreasing the ionic/radical products ratio.
- Imrie, C.,Modro, T. A.,Rohwer, E. R.,Wagener, C. C. P.
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p. 5643 - 5649
(2007/10/02)
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- THE SYNTHESIS, SOLVOLYSIS AND REARRANGEMENT OF BENZYL TRIFLUOROMETHANESULFINATES
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The synthesis and reactivity of benzyl trifluoromethanesulfinates have been investigated.These esters are easily and almost quantitatively obtained by selective oxidation of the corresponding sulfenates.A study of their behavior has revealed some unique features.In sharp contrast to benzyl arenesulfinates, which undergo ethanolysis with complete sulfur-oxygen bond fission, the corresponding trifluoromethanesulfinates undergo ethanolysis with exclusive carbon-oxygen bond fission, and with a rate enhancement by a factor of 6 powers of ten.The unusual high reactivity of these esters, comparable to that of the corresponding tosylates, is discussed.A kinetic study of the solvent and substituents effects on the rate of solvolysis has been performed.Also in contrast with benzyl arenesulfinates, these esters undergo facile rearrangement to sulfone on heating in polar nonhydroxylic solvents such as acetonitrile, in high yields.The mechanisms of solvolysis and rearrangement are discussed.
- Braverman, Samuel,Manor, Haim
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p. 357 - 365
(2007/10/02)
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- Sonochemical Enhancement of Phenylacetate Electrooxidation
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We report variously enhanced efficiencies, procedural improvements and altered product distributions from the electrooxidation of phenylacetate and p-chloro phenylacetate anions when performed under simultaneous ultrasonic irradiation.
- Walton, D.J.,Chyla, A.,Lorimer, J.P.,Mason, T.J.
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p. 1843 - 1852
(2007/10/02)
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- ELECTROCHEMICAL OXIDATION OF ORGANOSILICON COMPOUNDS I. OXIDATIVE CLEAVAGE OF CARBON-SILICON BOND IN ALLYLSILANES AND BENZYLSILANES
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Electrochemical oxidation of allylsilanes and benzylsilanes in the presence of alcohol, carboxylic acid, or water resulted in cleavage of the carbon-silicon bond and formation of the corresponding ether, ester, or alcohol, respectively.
- Yoshida, Jun-ichi,Murata, Toshiki,Isoe, Sachihiko
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p. 3373 - 3376
(2007/10/02)
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- MODIFICATION OF SINGLET CARBENE REACTIVITIES BY SOLVENT
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The solvent effect on the reactivity of singlet carbenes has been investigated.Competition reactions between pairs of alcohols for arylcarbenes in various solvents indicates that the O-H insertion selectivity is influenced only by 1,4-dioxane.Thus, phenylcarbene is some 33 times more reactive toward methanol relative to t-butyl alcohol in 90 molpercent dioxane than without solvent.Similar competition reactions between alcohol and olefin indicate that the O-H insertion-addition selectivities of arylcarbenes are considerably altered by dioxane.These results are interpreted as indicating that dioxane stabilizes singlet carbenes by complexing with its ione pairs of electrons.
- Tomoika, H.,Ozaki, Y.,Izawa, Y
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p. 4987 - 4994
(2007/10/02)
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- THE EFFECT OF ARYL SUBSTITUENTS ON ARYLCARBENE REACTIVITY
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Substituted (p-MeO, p-Me, H, p-Cl, p-Br, m-Br, m-MeO, 3,4-Cl2, p-CO2Me, m-CN and p-CN) monophenylcarbenes are generated in a binary mixture of substrates (methanol, cis-4-methyl-2-pentene and cyclohexane) and the relative rate of O - H insertion into methanol to stereospecific cyclopropanation of the olefin to C - H insertion into cyclohexane are calculated from the ratios of products and substrates.It is found (i) that the reactivities of the substrates decrease in the order of methanol, olefin and cyclohexane and (ii) that electron-donating substituents generally lead to reaction with the more reactive substrates while the reaction with the less reactive substrates is favoured in the case of electron-withdrawing substituents.These results are interpreted in terms of the change in the electrophilicity of the singlet arylcarbene by the substituents rather than the change in the singlet-triplet equilibrium.
- Tomioka, Hideo,Tabayashi, Kazuo,Ozaki, Yasuji,Izawa, Yasuji
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p. 1435 - 1440
(2007/10/02)
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- A NOVEL METHOXYMETHYLATION OF ARYL BROMIDE BY METHOXYMETHYLTRIBUTYLTIN IN THE PRESENCE OF PALLADIUM COMPLEX
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The reaction of aryl bromides with methoxymethyltributyltin in the presence of a catalytic amount of dichlorobis(triphenylphosphine)palladium was found to give arylmethyl methyl ether.The reaction is a novel aromatic methoxymethylation.
- Kosugi, Masanori,Sumiya, Takashi,Ogata, Toshimi,Sano, Hiroshi,Migita, Toshihiko
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p. 1225 - 1226
(2007/10/02)
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- Photochemistry of Halogenated Benzene Derivatives. Part 2. Photoreactions of α-Substituted p-Chlorotoluenes
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Solution-phase photoreactions of α-substituted p-chlorotoluenes of the general structure p-ClC6H4CH2X (X = H, Cl, CN, CO2H and OH) have been studied at wavelengths around 300 nm.The acetone-sensitized photolyses of the substrates with X = H, CN, CO2H and OH in deaerated CH3OH provided reductively dechlorinated photoproducts C6H5CH2X with yields of 10-52percent based on photodecomposed starting material.The photoreactions of p-chlorobenzyl chloride (2) proceeded through homolytical and heterolytical cleavage of its side-chain C-Cl bond possibly via a triplet excited state.The main product of the photochemical reactions of (2) in deaerated CH3OH both with and without acetone present was p-chlorobenzyl methyl ether.In order to achieve a better understanding of some photochemical aspects of the photolysis of substrate (2), the photoreactions of three halogenobenzaldehydes have been studied.The irradiation of p- and m-chloro- and m-bromo-benzaldehyde in deaerated CH3OH gave rise to the formation of the corresponding acetals as the sole principal products.The photoreactivity of m-BrC6H4CHO was 93 times greater than that of m-ClC6H4CHO.
- Choudhry, Ghulam Ghaus,Roof, Antonius Aloysius Maria,Hutzinger, Otto
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p. 2957 - 2962
(2007/10/02)
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