- EPR EVIDENCE FOR A SINGLE ELECTRON TRANSFER MECHANISM IN REACTIONS OF AROMATIC KETONES WITH LITHIUM AMIDES
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Direct spectroscopic evidence (EPR) supporting a single electron transfer mechanism in the reaction of lithium amides with aromatic ketones is presented.
- Ashby, E. C.,Goel, A. B.,DePriest, R. N.
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- Nickel-catalyzed deoxygenation of oxiranes: Conversion of epoxides to alkenes
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Deoxygenation of epoxides takes place under the catalysis of nickel in the presence of diethylzinc as a deoxygenation agent to yield alkenes. Epoxides with a wide variety of substitution patterns are deoxygenated in this catalytic system to give terminal, 1,1-disubstituted, 1,2-disubstituted, trisubstituted, and tetrasubstituted alkenes in high yields. Reactions of 1,2-disubstituted epoxides we examined proceeded in an E-stereoselective manner. High compatibility with other functional groups through this transformation was also observed.
- Mori, Takamichi,Takeuchi, Yoshihito,Hojo, Makoto
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supporting information
(2020/01/24)
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- An Isolable and Bench-Stable Epoxidizing Reagent Based on Triazine: Triazox
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A new triazine-based oxidizing reagent, 2-hydroperoxy-4,6-diphenyl-1,3,5-triazine (Triazox), has been developed. The reagent can be synthesized from inexpensive starting materials and is a bench-stable solid that is isolable in pure form. Epoxidation of alkenes possessing acid-sensitive functionalities using Triazox proceeded in good to excellent yields. The accompanying nonacidic triazinone coproduct can be easily removed by filtration. These features indicate that Triazox is a practically useful oxidizing reagent.
- Yamada, Kohei,Igarashi, Yuki,Betsuyaku, Tatsuki,Kitamura, Masanori,Hirata, Koki,Hioki, Kazuhito,Kunishima, Munetaka
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supporting information
p. 2015 - 2019
(2018/04/16)
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- Pinacol Rearrangement and Direct Nucleophilic Substitution of Allylic Alcohols Promoted by Graphene Oxide and Graphene Oxide CO2H
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Graphene oxide (GO) and carboxylic acid functionalized GO (GO–CO2H) have been found to efficiently promote the heterogeneous and environmentally friendly pinacol rearrangement of 1,2-diols and the direct nucleophilic substitution of allylic alcohols. In general, high yields and regioselectivities are obtained in both reactions using 20 wt % of catalyst loading and mild reaction conditions.
- Gómez-Martínez, Melania,Baeza, Alejandro,Alonso, Diego A.
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p. 1032 - 1039
(2017/03/27)
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- Iron-Catalyzed Ortho C-H Methylation of Aromatics Bearing a Simple Carbonyl Group with Methylaluminum and Tridentate Phosphine Ligand
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Iron-catalyzed C-H functionalization of aromatics has attracted widespread attention from chemists in recent years, while the requirement of an elaborate directing group on the substrate has so far hampered the use of simple aromatic carbonyl compounds such as benzoic acid and ketones, much reducing its synthetic utility. We describe here a combination of a mildly reactive methylaluminum reagent and a new tridentate phosphine ligand for metal catalysis, 4-(bis(2-(diphenylphosphanyl)phenyl)phosphanyl)-N,N-dimethylaniline (Me2N-TP), that allows us to convert an ortho C-H bond to a C-CH3 bond in aromatics and heteroaromatics bearing simple carbonyl groups under mild oxidative conditions. The reaction is powerful enough to methylate all four ortho C-H bonds in benzophenone. The reaction tolerates a variety of functional groups, such as boronic ester, halide, sulfide, heterocycles, and enolizable ketones.
- Shang, Rui,Ilies, Laurean,Nakamura, Eiichi
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supporting information
p. 10132 - 10135
(2016/08/31)
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- Metalloporphyrinic framework containing multiple pores for highly efficient and selective epoxidation
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Metalloporphyrin MnIIICl-5,10,15,20-tetrakis(3,5- biscarboxylphenyl)porphyrin, having eight carboxylate groups in multiple coordination modes, connects with paddle-wheel Zn2(COO)4 units for the construction of an interesting porous porphyrinic framework that demonstrates high efficiency and stability upon epoxidation of olefins with excellent substrate size selectivity.
- Yang, Xiu-Li,Wu, Chuan-De
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supporting information
p. 4797 - 4799
(2014/06/09)
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- Four metalloporphyrinic frameworks as heterogeneous catalysts for selective oxidation and aldol reaction
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Four porous metalloporphyrinic framework materials, [(CH3) 2NH2][Zn2(HCOO)2(Mn III-TCPP)]·5DMF·2H2O (1; H6TCPP = tetrakis(4-carboxyphenyl)porphyrin), [(CH3)2NH 2][Cd2(HCOO)2(MnIII-TCPP)] ·5DMF·3H2O (2), [Zn2(HCOO)(Fe III(H2O)-TCPP)]·3DMF·H2O (3), and [Cd3(H2O)6(μ2-O)(Fe III-HTCPP)2]·5DMF (4) were synthesized by heating a mixture of MIIICl-H4TCPP (M = Mn and Fe) and M′ (M′ = Zn or Cd) nitrate in a mixed solvent of DMF and acetic acid. Compounds 1-3 are built up from M′2(COO)4 paddle-wheel subunits bridged by MIII-TCPP and formate ligands to form their 3D connections. The formate pillar heterogeneously connects with M and M′ cations in 1 and 2 and homogeneously joins M′ cations in 3. The μ2-O bridged FeIII-HTCPP dimer performs as a decadentate ligand to link 10 cadmium cations for the formation of an interesting 3D coordination network of 4. The four porphyrinic frameworks present interesting catalytic properties in the selective epoxidation of olefins, oxidation of cyclohexane, and intermolecular aldol reaction of aldehydes and ketones.
- Zou, Chao,Zhang, Tianfu,Xie, Ming-Hua,Yan, Lijun,Kong, Guo-Qiang,Yang, Xiu-Li,Ma, An,Wu, Chuan-De
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p. 3620 - 3626
(2013/05/09)
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- Highly efficient C-H oxidative activation by a porous Mn III-porphyrin metal-organic framework under mild conditions
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A simple strategy to rationally immobilize metalloporphyrin sites into porous mixed-metal-organic framework (M'MOF) materials by a metalloligand approach has been developed to mimic cytochrome P450 monooxygenases in a biological system. The synthesized porous M'MOF of [Zn2(MnOH-TCPP)- (DPNI)]·0.5DMF·EtOH·5.5H2O (CZJ-1; CZJ = Chemistry Department of Zhejiang University; TCPP = tetra-kis(4-carboxyphenyl) porphyrin); DPNI = N, N′-di(4-pyridyl)-1, 4, 5, 8-naph- thalenetetracarboxydiimide) has the type of doubly interpenetrated cubic aPo topology in which the basic Zn2-(COO)4 paddle-wheel clusters are bridged by metalloporphyrin to form two-dimensional sheets that are further bridged by the organic pillar linker DPNI to form a three-dimensional porous structure. The porosity of CZJ-1 has been established by both crystal-lographic studies and gas-sorption isotherms. CZJ-1 exhibits significantly high catalytic oxidation of cyclohexane with conversion of 94% to the mixture of cyclohexanone (K) and cyclohexanol (A) (so-called K-A oil) at room temperature. We also provided solid experimental evidence to verify the catalytic reaction that occurred in the pores of the M'MOF catalyst.
- Xie, Ming-Hua,Yang, Xiu-Li,He, Yabing,Zhang, Jian,Chen, Banglin,Wu, Chuan-De
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p. 14316 - 14321
(2013/11/06)
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- Lewis acid-promoted electron transfer deoxygenation of epoxides, sulfoxides, and amine N-oxides: the role of low-valent niobium complexes from NbCl5 and Zn
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A mild and operationally simple deoxygenation of epoxides, sulfoxides, and amine N-oxides is described using a sub-stoichiometric amount of low-valent niobium complexes generated in situ from commercially available NbCl5 and zinc dust. The deoxygenation proceeds by a reductive cleavage of polarized O-C/O-N/O-S bonds through a single electron transfer from zinc metal to the niobium-substrate complex due to the high oxophilic nature of the niobium species. The presence of adjacent radical-stabilizing groups is beneficial to epoxide substrates; however the similar prerequisite does not apply to sulfoxides and amine N-oxides, where a broad range of substrates are efficiently deoxygenated in excellent yields.
- Oh, Kyungsoo,Knabe, William Eric
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supporting information; experimental part
p. 2966 - 2974
(2009/05/30)
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- o-benzenedisulfonimide as reusable bronsted acid catalyst for acid-catalyzed organic reactions
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Acid-catalyzed organic reactions, such as etherification, esterification, acetal synthesis, cleavage, and interconversion, and pinacol rearrangement were carried out in the presence of catalytic amounts of o-benzenedisulfonimide as Bronsted acid catalyst; the conditions were mild and selective. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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p. 1379 - 1388
(2008/12/21)
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- Solid-state organic reactions proceeding by pulverization: Oxidation and halogenation with iodosobenzene and inorganic solid-supports
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Pulverization-activation method was employed to accelerate solid-state organic reactions. Crushing and grinding of solid mixtures of hydrogen halide-treated silica gels, iodosobenzene and organic substrates in the absence of a solvent brought about smooth and rapid reactions to give halogenated and/or oxidized products in good yields. Various sulfides were smoothly converted to sulfonyl chlorides in one step in excellent yields. The surface of silica gel activated by pulverization serves as a reaction field on which reagent molecules can effectively encounter with each other.
- Sohmiya, Hajime,Kimura, Takahide,Fujita, Mitsue,Ando, Takashi
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p. 13737 - 13750
(2007/10/03)
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- Reactions of pinacols with one-electron oxidants
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Oxidation of the tetraarylpinacols (Ar2COH)2, 1a-e, in which Ar = C6H5 (1a), 4-ClC6H4 (1b), 4-MeC6H4 (1c), 4-MeOC6H4 (1d) and 4-Me2NC6H4 (1e), by thianthrene cation radical (Th?+) in CH3-CN and in CH2Cl2 led quantitatively to the corresponding diaryl ketones Ar2C=O (2a-e), provided a sufficient amount of base, 2,6-di-tert-butyl-4-methylpyridine (DTBMP), was present to prevent presumed acid-catalyzed rearrangement. In the case of 1e, continued oxidation of 2e was also observed. Oxidation of 1a by (4-BrC6H4)3N?+SbCl 6- and (4-BrC6H4)3N?+SbF 6- (Ar3N?+) occurred analogously. Evidence for the catalytic, cation-radical rearrangement of 1a by Ar3N?+ (reported in earlier literature) and by Th?+ could not be found. Quantitative oxidation of 1a to 2a and of 1d to 2d was obtained also with NOBF4, again provided that sufficient DTBMP was present to prevent acid-catalyzed rearrangement. Catalytic, oxidative rearrangement of 1d at room temperature and (as reported in earlier literature) at -5 °C was not observed. Oxidation was also observed of 2,3-diphenyl-2,3-butanediol (3) to acetophenone (9) and of 1,1-dimethyl-2,2-diphenylethanediol (4) to 2a and acetone by Th?+. Oxidation of 2,3-dimethyl-2,3-butanediol (5) by Th?+ was not observed. Instead, even in the presence of DTBMP, pinacolone (10) and tetramethyloxirane (11) were formed, through, it is proposed, a mechanism involving complexation with Th?+.
- Han, Dong Sul,Shine, Henry J.
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p. 3977 - 3982
(2007/10/03)
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- Synthesis of 2-Cyano-1,1,2,2-tetraphenylethyl Cation and Silver Ion Assisted Solvolysis of sym-Tetraphenylethylene Dichloride
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The reaction of 3-chloro-2,2,3,3-tetraphenylpropanenitrile (2) with AgSbF6 or SbCl5 below -55 deg C in methylene chloride produces the stable, long-lived cation 2-cyano-1,1,2,2-tetraphenylethyl cation (5).Treatment of 5 with TMSCN affords a 98percent yield of 2,2,3,3-tetraphenylsuccinonitrile.It was also found that cation 5 generated with AlCl3 at 0 deg C can undergo intramolecular aromatic substitution to give 9-(cyanodiphenylmethyl)fluorene (8).In the reactions of sym-tetraphenylethylene dichloride (1) with CF3COOAg in the presence of methanol, it was found that tetraphenylethanone dimethyl ketal (9) can be synthesized in 91percent yield.Because rearrangement occured, 1-methoxy-1,2,2,2-tetraphenylethyl cation (15) is proposed as a reaction intermediate.In contrast, treatment of dichloride 1 with CF3CO2Ag in the presence of phenol or isopropyl or allyl alcohol did not produce the corresponding ketals but the 1,3-dioxolane ortho esters 19, 20, or 21 (2-alkoxy-2-trifluoromethyl)-4,4,5,5-tetraphenyl-1,3-dioxolanes).
- Wo, Shiming,Zieger, Herman E.,Millar, Michelle M.,Koch, Stephen A.
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p. 5925 - 5930
(2007/10/03)
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- Aerobic Epoxidation of Hindered Olefins and Enol Ethers Catalyzed by a Polymerizable β-Ketoesterate Complex of Iron(III).
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Peculiar hindered olefins and derivatives have been epoxidized, under Mukaiyama's conditions, using iron(II) catalytic centres.The experimental results allow to rule out the involvement of singlet oxygen and free peroxyacids as active species.
- Lopez, Luigi,Mastrorilli, Piero,Mele, Guiseppe,Nobile, Cosimo F.
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p. 3633 - 3636
(2007/10/02)
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- TELLURIUM TETRACHLORIDE AS A MILD DEPROTECTION REAGENT FOR ACETALS AND THIOACETALS
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On treatment with tellurium tetrachloride in dichloromethane at room temperature, acetals and thioacetals are easily cleaved to regenerate original carbonyl compounds in good yields.
- Tani, Hiroyuki,Inamasu, Tokuo,Masumoto, Kazunori,Tamura, Rui,Shimizu, Hiroshi,Suzuki, Hitomi
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p. 261 - 266
(2007/10/02)
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- Zinc-Promoted Reactions. 1. Mechanism of the Clemmensen Reaction. Reduction of Benzophenone in Glacial Acetic Acid
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The mechanism of the Clemmensen reduction of diaryl ketones was investigated by reducing benzophenone, benzhydryl chloride, and dichlorodiphenylmethane in AcOH under a variety of conditions.Besides diphenylmethane, dimeric products were isolated that were indicative of the formation of radical species.Different product distributions were obtained from reactions run under different conditions.The reduction of deuteriated benzhydryl chloride was also performed.A quite complicated mechanistic pattern, involving ionic and nonionic reactions, emerged from the experimental p icture.Two pathways, connected through the protonated substrate, were recognized.According to the first pathway the reduction is promoted by a SET from Zn to the substrate, leading to the formation of a carbon radical having one zinc atom bound to the oxygen of the carbonyl group.Benzhydryl chloride, benzhydryl acetate, and dichlorodiphenylmethane are involved in the process.The product distributions suggest the occurrence of several SETs, which involve the formation of different radical species.Ionic reactions are responsible for the second route to the reduced products.Nucleophilic displacements also participate to the complex mechanism.
- Vona, Maria Luisa Di,Rosnati, Vittorio
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p. 4269 - 4273
(2007/10/02)
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- Influence of Solvent and Cation on the Properties of Oxygen-containing Organic Anions. Part 4. Mechanism and Reactivity of Tetraaryloxirane Cleavage with Alkali Metals
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Six tetraaryloxiranes 1a-f (Scheme 4) were reduced (Schemes 1-3) with alkali metals (M = Li, Na, K, Cs) in eight polar aprotic solvents under an inert atmosphere.The organometallic solutions thus obtained were hydrolysed and the reaction products analysed.Similar experiments were carried out where the same solutions were quenched with D2O or MeI.In some cases the same solutions were studied by NMR and ESR spectroscopy before quenching.A stepwise reduction mechanism was established where the transfer of a first electron produces CO-bond scission in the oxirane ring, yielding a short-lived radical anion 4 or 5 (Scheme 1), i. e., a tetraalkyl-β-oxidoethyl radical.This intermediate can either eliminate oxygen as metal oxide (MO) to produce a tetraarylethylene 24 (Scheme 2) or be further reduced to a dianion 8 or 9 (Scheme 1).This anion yields, upon hydrolysis, low yields,if any, of the corresponding tetraphenylethanol 15 or 16 (Z = H).The larger proportion of the dianion, after the first protonation step, yielding anion 11 or 22, undergoes CC-bond scission which leads eventually to the corresponding ketone and diarylmethane 19 + 20 or 21 + 23 (Z = H) (Scheme 2).Other possible pathways were excluded through experiments where other possible intermediates were generated.These led to different end products.A triparametric linear correlation as a function of solvent parameters ETN and DN, as well as the cationic radius, was established for the influence of the nature of the solvent and counter-ion on the ratio between the rates of formation of products stemming from metal oxide (MO) elimination by the ring-opened radical anion 4 or 5 (Schemes 1 and 2) and rates of formation of products stemming from further reduction of the same radical anion to the dianion 8 or 9, thus confirming the mechanism established.
- Franco, M. Luisa T. M. B.,Herold, Bernardo J.,Maercker, Adalbert
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p. 119 - 129
(2007/10/02)
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- Solid-State Organic Reactions Proceeding by Pulverization of Inorganic Solid-Supports. Reactions of Iodosobenzene with Unsaturated Hydrocarbons on Acid-Treated Silica Gel
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Pulverization of solid mixtures of hydrogen halide-treated silica gels, iodosobenzene, and alkenes or an alkyne in the absence of a solvent brings about smooth and rapid reaction to give halogenated or oxidized products in good yields.
- Sohmiya, Hajime,Kimura, Takahide,Bauchat, Patrick,Fujita, Mitsue,Ando, Takashi
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p. 1391 - 1392
(2007/10/02)
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- Novel reductive couplinog-rearrangement of carbonyl compounds with metal/Lewis acid under irradiation of ultrasonic wave
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Novel reductive coupling-rearrangement of carbonyl compounds such as benzophenones with Al or Zn/ AlCl3 in CH3CN under irradiation of ultrasonic wave gave benzopinacolones via epoxides in good yields.
- Sato, Ryu,Nagaoka, Takeshi,Saito, Minoru
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p. 4165 - 4168
(2007/10/02)
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- ELECTRON-TRANSFER CHAIN ISOMERIZATION OF EPOXIDES INDUCED BY ONE-ELECTRON OXIDIZING AGENTS
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One electron oxidizing agents have been employed to achieve the isomerization of epoxides to ketones.The reactions most likely proceed via a radical cation chain electron-transfer mechanism.
- Lopez, Luigi,Troisi, Luigino
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p. 3097 - 3100
(2007/10/02)
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- Pinacol-Pinacolone Rearrangement Promoted by Polyphosphoric Acid Trimethylsilyl Ester (PPSE)
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Pinacols afforded the corresponding pinacolones in high yields in the presence of the polyphosphoric acid trimethylsilyl ester (PPSE) at a temperature above 80 deg C.Tetraphenylethylene oxide, in addition to benzopinacolone, was obtained in the reaction of benzopinacol under milder conditions.The solvent effect suggested that the rearrangement proceeded via the carbonium-ion intermediate.
- Kakimoto, Masa-aki,Seri, Takuya,Imai, Yoshio
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p. 2643 - 2644
(2007/10/02)
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- PINACOL CLEAVAGE USING IRON(III)TRISPHENANTHROLINE COMPLEXES
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Oxidative bond cleavage of benzpinacol and 2,3-diphenyl-2,3-butanediol have been effected with two Fe(III)(1,10-phenantroline)3 complexes which are thought to undergo electron transfer reactions by an outer sphere mechanism.The products of these reactions are exclusively the corresponding ketones when 2,6-di-t-butylpyridine is added to the solution.In contrast to the facile oxidations of these aromatic substrates, pinacol is not cleaved under these reaction conditions.
- Penn, John H.,Deng, Dao-Li,Chai, Kyung-Jin
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p. 3635 - 3638
(2007/10/02)
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- Photoinduced Electron Transfer Reaction. Part 3. 9,10-Dicyanoanthracene-sensitized Photo-oxidation of Electron-rich Stilbene Oxides
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The 9,10-dicyanoanthracene (DCA)-sentisized photo-oxygenation of the electron-rich stilbene oxides (1) gives the ozonides (2) almost quantitatively.The fluorescence of DCA is quenched by (1) at a diffusion-controlled rate and the above reaction is quenched by polymethoxybenzenes which indicates that an electron transfer mechanism is involved.The quantum yield for ozonide formation varies from 0.6 for trans-2-(4-methoxyphenyl)-3-phenyloxirane (1d) to 2.4 for trans-2,3-bis(4-methoxyphenyl)-2,3-diethyloxirane (1h), suggesting a duplex reaction mechanism such as photo-oxygenation by superoxide and a Barton mechanism after the initial electron transfer from the epoxides (1) to the excited singlet state of DCA.
- Futamura, Shigeru,Kusunose, Shosaku,Ohta, Hiroyuki,Kamiya, Yoshio
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- 2,4,4,6-Tetrabromocyclohexa-2,4-dienone: a New Electron Acceptor in the Photosensitized Oxidation of Unsaturated Substrates
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2,4,4,6-Tetrabromocyclohexa-2,4-dienone, usually used as a mild and selective brominating agent, acts as an electron acceptor in the sensitized photo-oxygenation of several unsaturated substrates; a mechanism is proposed.
- Lopez, Luigi,Calo, Vincenzo
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p. 1266 - 1268
(2007/10/02)
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- The Reaction of Chlorosulfonyl Isocyanate with Epoxides. A Novel Conversion of Epoxides to Cyclic Carbonates
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The facile reaction of chlorosulfonyl isocyanate (CSI) with epoxides is described.The initially formed 2-chlorosulfonylimino-1,3-dioxolane 2a-e and N-chlorosulfonyl-1,3-oxazolidin-2-one 3a-e derivatives undergo smooth hydrolysis to yield the corresponding 1,3-dioxolan-2-one 4a-e and 1,3-oxazolidin-2-one 5a-e derivatives respectively.This reaction sequence provides a convenient one-pot method for the conversion of epoxides to cylic carbonates.Substrates such as 1g-i are exceptions to this otherwise general reaction pathway.
- Keshava Murthy, K. S.,Dhar, D. N.
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p. 1721 - 1725
(2007/10/02)
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- Electron-Transfer Photooxygenation. 5. Oxidation of Phenyl-Substituted Alkenes Sensitized by Cyanoanthracenes
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The electron-deficient sensitizers 9,10-dicyanoanthracene (DCA) and 9-cyanoanthracene (CNA) sensitize the photooxidation of 1,1-diphenylethylene (1), trans- and cis-stilbene (12 and 14), and tetraphenylethylene (18) in oxygen-saturated polar solvents.The photoproducts in MeCN include the cleavage products Ph2CO and PhCHO, the epoxides, and, in the case of the stilbenes, cis-trans isomerized olefin.Quantum yields for disappearance of the alkenes are 0.8, 0.5, 0.2, and 0.15 for 1, 12, 14, and 18, respectively.No photooxygenation takes place in nonpolar solvents.The reactions in MeCN are accompanied by quenching of the DCA and CNA fluorescence.The measured quenching rate constants closely resemble values calculated for an electron-transfer process and agree, withing experimental error, with those determined from the acceptor concentration dependence of product formation.The photooxygenations are quenched by addition of small amounts of compounds of lower oxidation potential than that of the alkenes, whereas compounds of higher oxidation potential have little effect.All results are consistent with an electron-transfer mechanism involving a donor radical cation and sensitizer radical anion which subsequently reduces oxygen to superoxide.The data are not compatible with a singlet oxygen mechanism.
- Eriksen, J.,Foote, C. S.
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p. 6083 - 6088
(2007/10/02)
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