- Direct synthesis of dimethylbiphenyls by toluene coupling in the presence of palladium triflate and triflic acid
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A direct coupling reaction of toluene for synthesis of DMBP is reported in the presence of a strong acid, such as trifluoromethane sulfonic acid (TfOH) and Pd(II)triflate (Pd(TfO)2), at room temperature. The presence of both Pd(TfO)2 and TfOH was crucial for an effective coupling of toluene. The reaction rate was promoted by H+ when the anion was labile such as OTf- so that the overall reactivity of the Pd(II)/HOTf system was greater than that reported by others for the Pd(II) system in weaker acids such as acetic or trifluoroacetic acid. Increasing acid strength to favor coupling in the 3- and 4- positions altered the regioselectivity.
- Xu, Bo-Qing,Sood, Dhiraj,Iretskii,White, Mark G.
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- OXIDATION OF METHYL-SUBSTITUTED BIPHENYL COMPOUNDS
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A process for oxidizing methyl-substituted biphenyl compounds comprises contacting a mixture comprising isomers of at least one methyl-substituted biphenyl compound with a source of oxygen, wherein the mixture comprises at least 20 wt% of isomer(s) having a methyl group at a 2-position or a 3-position on at least one benzene ring and at least 50 wt% of isomer(s) having a methyl group at a 4-position on at least one benzene ring, wherein said percentages are based on the total weight of the at least one methylbiphenyl compound in the mixture.
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Paragraph 0064-0066
(2017/11/04)
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- Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
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A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
- Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
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supporting information; experimental part
p. 6146 - 6159
(2012/05/07)
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- Palladium-catalysed synthesis of nonsymmetrically disubstituted-1,1′- biphenyls from o-substituted aryl iodides through aryl coupling and delayed hydrogenolysis
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In the presence of Pd(OAc)2 and norbornene as catalysts, two molecules of an ortho-substituted aryl iodide undergo aryl-aryl coupling to a palladium-bonded biphenylyl intermediate, which is hydrogenolyzed by benzyl alcohol to give 2,3′-disubsti
- Deledda, Sara,Motti, Elena,Catellani, Marta
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p. 741 - 747
(2007/10/03)
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- A Re-examination of the Sonochemical Coupling of Bromoaryls.
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The sonochemical coupling of bromotoluenes leads to a mixture of isomeric bitolyls suggesting a radical mechanism, confirmed using radical scavengers which inhibit the reaction.
- Price, Gareth J.,Clifton, Andrew A.
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p. 7133 - 7134
(2007/10/02)
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- Activation of Aromatic Carbon-Hydrogen Bonds by Palladium(II) Acetate-Dialkyl Sulfide Systems. Formation and Characterization of Novel Diphenyltripalladium(II) Complexes
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Palladium(II) acetate reacts wuth benzene in the presence of dialkyl sulfides at 70 deg C to afford novel diphenyltripalladium(II) complexes of 1SR2)PhPd(μ-MeCO2)2Pd(μ-MeCO2)2PdPh(R1SR2)> (1a; R1=But, R2=CH2But; 1b; R1=R2=But: 1c; R1=R2=Pri; 1d; R1=R2=Et) Adducts, tSCH2Bu')2> and i2)2>, prepared by the reactions of palladium(II) acetate and the corresponding dilakyl sulfides in benzene at 5-10 deg C, change to 1a and 1c, respectively, on heating in benzene at 70 deg C.In contrast, reactions of palladium(II) acetate with toluene or thiophene in the presence od diisopropyl sulfide afford no isolable tolyl- or thienyl-palladium species, but coupling products, i.e. bitolyls or bithienyls, are detected by GLC analysis.Treatment of 1b with styrene produces trans-stilbene, whereas 1c reacts with carbon monoxide as well as carbon dioxide to yield benzoic acid.When palladium(II) acetate and t-butyl phenethyl sulfide are heated at 80 deg C in benzene, an adduct tSCH2CH2Ph)2> is formed, in sharp contrast with the case of benzyl t-butyl sulfide, which gives a cyclopalladated complex under the same reaction conditions.
- Fuchita, Yoshio,Hiraki, Katsuma,Kamogawa, Yasuko,Suenaga, Miho,Tohgoh, Kazutaka,Fujiwara, Yuzo
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p. 1081 - 1085
(2007/10/02)
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- Catalytic Formation of Biaryls from Arenes through C-H Bond Activation by RhCl(CO)(PMe3)2 under Irradiation
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Arenes were dehydrogenatively coupled into biaryls catalyzed by RhCl(CO)(PMe3)2 at room temperature under irradiation.The regioselectivity obtained in the reaction of toluene suggested the presence of a radical intermediate.
- Sakakura, Toshiyasu,Sodeyama, Touru,Tokunaga, Yuko,Tanaka, Masato
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p. 2211 - 2214
(2007/10/02)
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- Reactivity of Chalcogen Cluster Polycations
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The chalcogen polycations S8(AsF6)2, S19(HS2O7)2, and Se4(HS2O7)2 are powerful oxidants entering into electron transfer reactions with hydrocarbons, aromatic compounds, and halides.
- Rosan, A. M.
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p. 377 - 378
(2007/10/02)
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- The Role of Aroyloxyl Radicals in the Formation of Solvent-derived Products in Photodecomposition of Diaroyl Peroxides. The Reactivity of Substituted Cyclohexadienyl Radicals and Intermediacy of ipso Intermediates
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Photolyses of bis(2-thiophenecarbonyl)peroxide (TPO) in benzene and toluene afforded, among free-radical products, biphenyl and dimethylbiphenyls, respectively, which were solely derived from the aromatic solvents.The yields of biphenyls depended upon the rate with which the radical intermediates were generated from the peroxides in sufficiently high concentrations for their dimerization.Photolyses of TPO and dibenzoyl peroxide in 1,3,5-trimethylbenzene afforded also a solvent-derived products, 2,3',4,5',6-pentamethyldiphenylmethane.Its formation provides clear evidence for participation of cyclohexadienyl radicals bearing the aroyloxyl group on the methyl-substituted ipso carbon atom.
- Takahara, Shigeru,Urano, Tishiyuki,Kitamura, Akihide,Sakuragi, Hirochika,Kikuchi, Osamu,et al
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p. 688 - 697
(2007/10/02)
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- PALLADIUM(II)-CATALYZED OXIDATIVE COUPLING OF ARENES BY THALLIUM(III)
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Oxidation of benzenes with electron-donating and moderate electron-withdrawing substituents by thallium(III) trifluoroacetate in the presence of catalytic amounts of palladium(II) acetate affords biaryls in good yields.The GLC study of the isomer distribution has shown that 4,4'-biaryls are the major products.Thus, the 4,4'-biaryls can be easily isolated either by recrystallization or column chromatography.The competitive experiments and kinetic study using arenes and arylthallium derivatives as starting materials as well as quenching experiments have demonstrated the first step of the reaction to be fast thallation of arene to form arylthallium intermediate ArTl(OOCCF3)2.The latter undergoes the rate-determining transmetallation step reacting with monomeric complex Pd(OAc)2, which is formed upon depolymerization of trimer Pd3(OAc)6.Subsequent fast decomposition of arylpalladium species gives the final reaction products.The thallation of arene and substitution of TlIII for PdII in ArTl(OOCCF3)2 are characterized by the slopes of Hammet plots of -5.6 (?+) and -3.0 (?), respectively.
- Yatsimirsky, Anatoly K.,Deiko, Sergei A.,Ryabov, Alexander D.
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p. 2381 - 2392
(2007/10/02)
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- REACTION OF DIMETHYL SULFITE WITH PHENYLLITHIUM. FORMATION OF BIPHENYL AND DIPHENYL SULFIDE VIA SULFURANE
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Dimethyl sulfite reacted an excess of phenyllithium yielding biphenyl and diphenyl sulfide in good yield.Other dialkyl sulfites also reacted giving identical yields of biphenyl and diphenyl sulfide irrespective of the structure of the aryl groups, indicating that dialkyl sulfites can be used for the reaction with aryllithiums in place of diaryl sulfoxides.The mechanism of the reaction of diaryl sulfoxides with aryllithium is discussed on the the basis of the isomer distribution of bitolyls, the effect of additives, and the ratio of the benzyne and sulfonium salt pathways.Sulfurane 1 is formed in an initial stage of the reaction of diaryl sulfoxide with aryllithium followed by its competitive collapse by way of benzyne and sulfonium salt pathways.
- Hara, Yoshinori,Matsuda, Minoru
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p. 211 - 222
(2007/10/02)
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- Classification of the External Magnetic Field Effects on the Photodecomposition Reaction of Dibenzoyl Peroxide
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The external magnetic field effects upon product yields in the singlet sensitized photolysis of dibenzoyl peroxide in toluene were studied.The observed field dependencies were classified into four types, and were interpreted in terms of the electronic Zeeman and hyperfine interactions in the intermediate radical pair.Especially large magnetic field effects were observed for the yields of dimethylbiphenyls, new products in this reaction.
- Sakaguchi, Yoshio,Hayashi, Hisaharu,Nagakura, Saburo
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- A New Assisted Reaction in the Photodecomposition Reaction of Dibenzoyl Peroxide
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2,2'-, 2,3'-, and 3,3'-Dimethylbiphenyls were found in the photodecomposition reaction of dibenzoyl peroxide using toluene as solvent.We carried out the experiments to study the external magnetic field, oxygen scavenging, and excitation light intensity effects on their yields.It is concluded that they are produced through the dimerization of (benzoyloxy)methylcyclohexadienyl radicals.This is a new case of the assisted reaction by benzoyloxyl radical.The yields of dimethylbiphenyls were found to be affected remarkably by the small variation of the concentration of benzoyloxyl radical through the three experiments.
- Sakaguchi, Yoshio,Hayashi, Hisaharu,Nagakura, Saburo
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p. 3059 - 3063
(2007/10/02)
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- The Reductive Coupling of Organic Halide Using Hydrazine and a Palladium Amalgam Catalyst. I. The Preparation of Biaryls
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Iodoarenes could be converted to the corresponding biaryls in high yields by use of a catalytic amount of a palladium amalgam in place of a palladium-calcium carbonate catalyst in Busch's reaction.The 2,3'-isomer content in the bitolyls obtained by the homo-coupling of o-iodotoluene was 15percent when palladium was used, while it was 1percent when a palladium amalgam was used, and the latter was re-usable.The present method is further applicable to some iodoalkanes.
- Nakajima, Riichiro,Shintani, Yuji,Hara, Tadashi
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p. 1767 - 1768
(2007/10/02)
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