- Spectroscopic Analyses on Reaction Intermediates Formed during Chlorination of Alkanes with NaOCl Catalyzed by a Nickel Complex
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The spectroscopic, electrochemical, and crystallographic characterization of [(Me,HPyTACN)NiII(CH3CN)2](OTf)2 (1) (Me,HPyTACN = 1-(2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane, OTf = CF3SO3) is described together with its reactivity with NaOCl. 1 catalyzes the chlorination of alkanes with NaOCl, producing only a trace amount of oxygenated byproducts. The reaction was monitored spectroscopically and by high resolution electrospray-mass spectrometry (ESI-MS) with the aim to elucidate mechanistic aspects. NaOCl reacts with 1 in acetonitrile to form the transient species [(L)NiII-OCl(S)]+ (A) (L = Me,HPyTACN, S = solvent), which was identified by ESI-MS. UV/vis absorption, electron paramagnetic resonance, and resonance Raman spectroscopy indicate that intermediate A decays to the complex [(L)NiIII-OH(S)]2+ (B) presumably through homolytic cleavage of the O-Cl bond, which liberates a Cl? atom. Hydrolysis of acetonitrile to acetic acid under the applied conditions results in the formation of [(L)NiIII-OOCCH3(S)]2+ (C), which undergoes subsequent reduction to [(L)NiII-OOCCH3(S)]2+ (D), presumably via reaction with OCl- or ClO2-. Subsequent addition of NaOCl to [(L)NiII-OOCCH3(S)]+ (D) regenerates [(L)NiIII-OH(S)]2+ (B) to a much greater extent and at a faster rate. Addition of acids such as acetic and triflic acid enhances the rate and extent of formation of [(L)NiIII-OH(S)]2+ (B) from 1, suggesting that O-Cl homolytic cleavage is accelerated by protonation. Overall, these reactions generate Cl? atoms and ClO2 in a catalytic cycle where the nickel center alternates between Ni(II) and Ni(III). Chlorine atoms in turn react with the C-H bonds of alkanes, forming alkyl radicals that are trapped by Cl? to form alkyl chlorides.
- Draksharapu, Apparao,Codolà, Zoel,Gómez, Laura,Lloret-Fillol, Julio,Browne, Wesley R.,Costas, Miquel
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Read Online
- FREE RADICAL HALOGENATION OF ALKANES INITIATED BY TRANSITION METAL COMPLEXES
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Reaction between halocarbons (particularly CCl4) and hydrocarbons (particularly c-C6H12) in the presence of a range of low valent metal complexes have been investigated.A delaited study of the reaction involving has shown it to proceed by a free radical chain route in which the metal complex acts solely as an initiator.Similar behaviour has been confirmed for . (Re2(CO)10> and show initiation efficiencies comparable with organic peroxides, but other complexes are less efficient.Factors effecting efficiencies have been studied.
- Davis, Reg,Durrant, Jim L. A.,Rowland, Christopher C.
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Read Online
- Catalytic Bromination of Alkyl sp3C-H Bonds with KBr/Air under Visible Light
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Alkyl sp3C-H bonds of cycloalkanes and functional branch/linear alkanes have been successfully brominated with KBr using air or O2 as an oxidant at room temperature to 40 °C. The reactions are carried out in the presence of catalytic NaNO2 in 37% HCl (aq)/solvent under visible light, combining aerobic oxidations and photochemical radical processes. For various alkane substrates, CF3CH2OH, CHCl3, or CH2Cl2 is employed as an organic solvent, respectively, to enhance the efficiency of bromination.
- Zhao, Mengdi,Lu, Wenjun
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supporting information
p. 5264 - 5267
(2018/09/12)
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- Silica gel-mediated hydrohalogenation of unactivated alkenes using hydrohalogenic acids under organic solvent-free conditions
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Silica gel-mediated hydrochlorination of unactivated alkenes using 35% hydrochloric acid under organic solvent-free conditions proceeded to give the corresponding chlorides in good yields. Hydrobromination or hydriodination using 47% hydrobromic acid or 55% hydriodic acid afforded the corresponding halides, respectively. Silica gel could be recycled five times without any significant loss of activities.
- Tanemura, Kiyoshi
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supporting information
p. 4293 - 4298
(2018/11/10)
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- Metal-free regioselective hydrochlorination of unactivated alkenes via a combined acid catalytic system
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A combined acid HCl/DMPU-acetic acid catalytic system was used in the hydrochlorination of a wide range of unactivated alkenes. This hydrochlorination strategy is remarkably greener than previous reported methods in terms of high atom efficiency, no toxic waste generated and metal-free process. The higher efficiency, compared with other commercially available HCl reagents, was augmented by the good regioselectivity and functionality tolerance found. A stepwise mechanism for this hydrochlorination process was proposed based on kinetic studies.
- Liang, Shengzong,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 680 - 684
(2018/02/14)
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- Highly selective halogenation of unactivated C(sp3)-H with NaX under co-catalysis of visible light and Ag@AgX
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The direct selective halogenation of unactivated C(sp3)-H bonds into C-halogen bonds was achieved using a nano Ag/AgCl catalyst at RT under visible light or LED irradiation in the presence of an aqueous solution of NaX/HX as a halide source, in air. The halogenation of hydrocarbons provided mono-halide substituted products with 95% selectivity and yields higher than 90%, with the chlorination of toluene being 81%, far higher than the 40% conversion using dichlorine. Mechanistic studies demonstrated that the reaction is a free radical process using blue light (450-500 nm), with visible light being the most effective light source. Irradiation is proposed to cause AgCl bonding electrons to become excited and electron transfer from chloride ions induces chlorine radical formation which drives the substitution reaction. The reaction provides a potentially valuable method for the direct chlorination of saturated hydrocarbons.
- Liu, Shouxin,Zhang, Qi,Tian, Xia,Fan, Shiming,Huang, Jing,Whiting, Andrew
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p. 4729 - 4737
(2018/10/23)
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- A General Strategy for Aliphatic C-H Functionalization Enabled by Organic Photoredox Catalysis
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Synthetic transformations that functionalize unactivated aliphatic C-H bonds in an intermolecular fashion offer unique strategies for the synthesis and late-stage derivatization of complex molecules. Herein we report a general approach to the intermolecular functionalization of aliphatic C-H bonds using an acridinium photoredox catalyst and phosphate salt under blue LED irradiation. This strategy encompasses a range of valuable C-H transformations, including the direct conversions of a C-H bond to C-N, C-F, C-Br, C-Cl, C-S, and C-C bonds, in all cases using the alkane substrate as the limiting reagent. Detailed mechanistic studies are consistent with the intermediacy of a putative oxygen-centered radical as the hydrogen atom-abstracting species in these processes.
- Margrey, Kaila A.,Czaplyski, William L.,Nicewicz, David A.,Alexanian, Erik J.
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supporting information
p. 4213 - 4217
(2018/04/05)
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- Mild Aliphatic and Benzylic Hydrocarbon C-H Bond Chlorination Using Trichloroisocyanuric Acid
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We present the controlled monochlorination of aliphatic and benzylic hydrocarbons with only 1 equiv of substrate at 25-30 °C using N-hydroxyphthalimide (NHPI) as radical initiator and commercially available trichloroisocyanuric acid (TCCA) as the chlorine source. Catalytic amounts of CBr4 reduced the reaction times considerably due to the formation of chain-carrying ·CBr3 radicals. Benzylic C-H chlorination affords moderate to good yields for arenes carrying electron-withdrawing (50-85%) or weakly electron-donating groups (31-73%); cyclic aliphatic substrates provide low yields (24-38%). The products could be synthesized on a gram scale followed by simple purification via distillation. We report the first direct side-chain chlorination of 3-methylbenzoate affording methyl 3-(chloromethyl)benzoate, which is an important building block for the synthesis of vasodilator taprostene.
- Combe, Sascha H.,Hosseini, Abolfazl,Parra, Alejandro,Schreiner, Peter R.
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p. 2407 - 2413
(2017/03/11)
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- Visible Light-Induced Oxidative Chlorination of Alkyl sp3 C-H Bonds with NaCl/Oxone at Room Temperature
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A visible light-induced monochlorination of cyclohexane with sodium chloride (5:1) has been successfully accomplished to afford chlorocyclohexane in excellent yield by using Oxone as the oxidant in H2O/CF3CH2OH at room temperature. Other secondary and primary alkyl sp3 C-H bonds of cycloalkanes and functional branch/linear alkanes can also be chlorinated, respectively, under similar conditions. The selection of a suitable organic solvent is crucial in these efficient radical chlorinations of alkanes in two-phase solutions. It is studied further by the achievement of high chemoselectivity in the chlorination of the benzyl sp3 C-H bond or the aryl sp2 C-H bond of toluene.
- Zhao, Mengdi,Lu, Wenjun
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supporting information
p. 4560 - 4563
(2017/09/11)
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- A mild method for the replacement of a hydroxyl group by halogen. 1. Scope and chemoselectivity
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α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.
- Munyemana, Fran?ois,George, Isabelle,Devos, Alain,Colens, Alain,Badarau, Eduard,Frisque-Hesbain, Anne-Marie,Loudet, Aurore,Differding, Edmond,Damien, Jean-Marie,Rémion, Jeanine,Van Uytbergen, Jacqueline,Ghosez, Léon
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p. 420 - 430
(2015/12/31)
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- C-HALOGEN BOND FORMATION
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Methods of halogenating a carbon containing compound having an sp3 C-H bond are provided. Methods of fluorinating a carbon containing compound comprising halogenation with Cl or Br followed by nucleophilic substitution with F are provided. Methods of direct oxidative C-H fluorination of a carbon containing compound having an sp3 C-H bond are provided. The halogenated products of the methods are provided.
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Paragraph 0111-0118
(2013/03/26)
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- Chlorination of hydrocarbons with CCl4 catalyzed by complexes of Mn, Mo, V, Fe
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Catalytic chlorination of alkanes, cycloalkanes, and adamantane utilizing tetrachloromethane as the source of chlorine and applying catalysts containing manganese, molybdenum, vanadium, and iron activated with nitrile ligands, alcohols, and water was fulfilled. The optimum ratios of catalysts and reagents and the best reaction conditions were found for selective synthesis of chlorine-substituted hydrocarbons derivatives. Pleiades Publishing, Ltd., 2013.
- Khusnutdinov,Shchadneva,Bayguzina,Oshnyakova,Mayakova,Dzhemilev
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p. 1557 - 1566
(2014/02/14)
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- Manganese porphyrins catalyze selective C-H bond halogenations
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We report a manganese porphyrin mediated aliphatic C-H bond chlorination using sodium hypochlorite as the chlorine source. In the presence of catalytic amounts of phase transfer catalyst and manganese porphyrin Mn(TPP)Cl 1, reaction of sodium hypochlorite with different unactivated alkanes afforded alkyl chlorides as the major products with only trace amounts of oxygenation products. Substrates with strong C-H bonds, such as neopentane (BDE =~100 kcal/mol) can be also chlorinated with moderate yield. Chlorination of a diagnostic substrate, norcarane, afforded rearranged products indicating a long-lived carbon radical intermediate. Moreover, regioselective chlorination was achieved by using a hindered catalyst, Mn(TMP)Cl, 2. Chlorination of trans-decalin with 2 provided 95% selectivity for methylene-chlorinated products as well as a preference for the C2 position. This novel chlorination system was also applied to complex substrates. With 5α-cholestane as the substrate, we observed chlorination only at the C2 and C3 positions in a net 55% yield, corresponding to the least sterically hindered methylene positions in the A-ring. Similarly, chlorination of sclareolide afforded the equatorial C2 chloride in a 42% isolated yield. Regarding the mechanism, reaction of sodium hypochlorite with the MnIII porphyrin is expected to afford a reactive MnVO complex that abstracts a hydrogen atom from the substrate, resulting in a free alkyl radical and a MnIV-OH complex. We suggest that this carbon radical then reacts with a MnIV-OCl species, providing the alkyl chloride and regenerating the reactive MnVO complex. The regioselectivity and the preference for CH2 groups can be attributed to nonbonded interactions between the alkyl groups on the substrates and the aryl groups of the manganese porphyrin. The results are indicative of a bent [MnvO-H-C] geometry due to the C-H approach to the MnvO (dπ-pπ)* frontier orbital.
- Liu, Wei,Groves, John T.
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supporting information; experimental part
p. 12847 - 12849
(2010/11/05)
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- An efficient method for chlorination of alcohols using PPh3/Cl3CCONH2
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A new and convenient method for the chlorination of alcohols utilizing PPh3/Cl3CCONH2 is addressed. Various alcohols could smoothly be converted into their corresponding alkyl chlorides in high yield under mild conditions with short reaction times. A mechanism is disclosed with the evidence of inversion of configuration of the analogous alkyl chloride derived from R-(-)-2-octanol.
- Pluempanupat, Wanchai,Chavasiri, Warinthorn
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p. 6821 - 6823
(2007/10/03)
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- Photocatalytic oxidation of alkanes with dioxygen by visible light and copper(II) and iron(III) chlorides: Preference oxidation of alkanes over alcohols and ketones
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Visible light irradiation of alkanes in acetonitrile with CuCl2 and FeCl3 catalysts under atmospheric dioxygen gave the corresponding alcohols and ketones effectively; in these reactions, the total selectivity of the products did not decrease so much with increase of alkane conversion. For example, cyclohexanol and cyclohexanone were formed with ca. 70% selectivity at 50% conversion, because overoxidation of the products took place more slowly than cyclohexane oxidation. The relative reactivity values of cycloalkanes increased as their ring-sizes decreased. In the oxidation of hexane, the reactivity ratio of C1-/C2-/C3-H was found to be 1.0/1.4/1.8 with CuCl2 and 1.0/4.6/6.6 with FeCl3, respectively. Toluene and diphenylmethane were more reactive than cyclohexane with FeCl3, as expected, whereas the alkane was oxidized faster than the benzylic compounds in the separate reaction with CuCl2. Moreover, the alkane oxidation could be comparably performed by sunlight instead of an artificial lamp.
- Takaki, Ken,Yamamoto, Jun,Komeyama, Kimihiro,Kawabata, Tomonori,Takehira, Katsuomi
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p. 2251 - 2255
(2007/10/03)
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- Catalytic process for regiospecific chlorination of alkanes, alkenes and arenes
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The present invention provides a process for regiospecific chlorination of an aromatic or aliphatic compound with a chlorine source comprising a metal chloride and other than Cl2and SO2Cl2in presence of hypervalent iodine catalyst and in acidic medium.
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Page column 7
(2008/06/13)
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- Process for preparing alkyl halides
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In the preparation of alkyl halides from cycloaliphatic olefins and hydrohalic acids, the reaction is carried out at a temperature below the boiling point of the olefin without the addition of catalyst and without a solvent. At a high olefin conversion rate, alkyl halides are obtained with high selectivity and with very good color quality.
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- Oxygen activation by metal complexes and alkyl hydroperoxides. Applications of mechanistic probes to explore the role of alkoxyl radicals in alkane functionalization
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The mechanism of the oxidation of cycloalkanes by tertiary alkyl hydroperoxides catalysed by iron(III) dichlorotris(2-pyridylmethyl)amine IIICl2(TPA)>+ and by the acetate bridged (μ-oxo) di-iron complex III(TPA)2O(OAc)>3+ has been investigated.Product studies do not support oxidation via a high valent iron-oxo intermediate (formally FeV=O), but are consistent with a mechanism involving hydrogen atom abstraction from the alkane by alkoxyl radicals derived from the hydroperoxide.In the presence of a large excess of tert-butyl hydroperoxide, the oxidation of cyclohexane yields cyclohexanone, cyclohexanol and tert-butylcyclohexyl peroxide in more than stoichiometric amounts and, in the case of the mono-iron catalyst, one equivalent of cyclohexyl choride.Replacement of Me3COOH by hydroperoxides, which could yield tert-alkoxyl radicals having much shorter lifetimes than the tert-butoxyl radical prevents oxidation of the cycloalkane.The products obtained with these hydroperoxide mechanistic probes are those derived from the fast unimolecular reactions (generally β-scissions) of the corresponding alkoxyl radicals.The inapplicability of dimethyl sulfide as a mechanistically diagnostic trap for the putative FeV=O intermediate and the value of di-tert-butyl hyponitrite as a non-iron-based source of tert-butoxyl radicals are discussed.
- MacFaul, Philip A.,Arends, Isabella W. C. E.,Ingold, Keith U.,Wayner, Danial D. M.
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p. 135 - 146
(2007/10/03)
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- The functionalization of saturated hydrocarbons. Part 31. The Fe(pa)3 - and [Fe(tpa)Cl2]ClO4 - catalyzed oxidations of saturated hydrocarbons by hydrogen peroxide: A comparative mechanistic study
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The Fe(pa)3 and [Fe(tpa)Cl2]ClO4 catalyzed (pa = picolinic acid, tpa = tris(2-pyridylmethyl)amine) functionalization of saturated hydrocarbons by H2O2 in pyridine/acetic acid follows a common reaction pathway. Regioselectivity studies indicate, that a high valent iron species is responsible for the activation of the alkane. Alkyl hydroperoxides are the precursors for ketone and alcohol formation. Dioxygen provides the oxygen atoms in the alkyl hydroperoxide.
- Barton,Beck,Taylor
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p. 5245 - 5254
(2007/10/02)
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- C-H bond activation by metal oxo species: Chromyl chloride oxidations of cyclooctane, isobutane, and toluene
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Chromyl chloride, CrO2Cl2, oxidizes cyclooctane, isobutane, and toluene under mild conditions (25-60 °C). The reactions give chlorinated products (chlorocyclooctane, tert-butyl chloride, and benzyl chloride) and a dark chromium-containing precipitate. Hydrolysis of the precipitate yields oxygenated products, such as ketones, aldehydes, chloro ketones, epoxides, and alcohols. Kinetic data show that all of the reactions are first order in CrO2Cl2 and first order in substrate, with no sign of an induction period. Primary isotope effects have been observed for t-d1-isobutane and d8-toluene. The kinetic and mechanistic data indicate that the reactions proceed by initial hydrogen atom transfer from the substrate to CrO2Cl2 The rates of hydrogen atom abstraction by CrO2Cl2 vary in the order cyclohexane ? and ΔS?, indicating a common mechanism for the four substrates. The pathways leading from the initially formed alkyl radicals to the observed products are described. The ability of CrO2Cl2 to abstract a hydrogen atom from alkanes is remarkable, as it is a closed-shell, diamagnetic species, not a radical. It is proposed that the hydrogen atom abstracting ability derives from the strong O-H bond formed on hydrogen atom transfer, in [Cl2(O)Cr(OH)]. The rates of the CrO2Cl2 reactions correlate with rates of hydrogen atom abstraction by oxygen radicals, assuming a CrO-H bond strength of 83 kcal/mol (similar to that in HMnO4-). The implications of this perspective for transition metal mediated hydrogen atom transfer reactions are discussed.
- Cook, Gerald K.,Mayer, James M.
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p. 7139 - 7156
(2007/10/02)
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- The functionalization of saturated hydrocarbons. Part 25. Ionic substitution reactions in GoAggIV chemistry: The formation of carbon-halogen bonds
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GoAggIV chemistry (Fe (III) species, tert-butyl hydroperoxide in a mixture of pyridine and acetic acid) in the presence of LiCl can transform saturated hydrocarbons efficiently into the corresponding alkyl chlorides. The transformation into monosubstituted alkyl derivatives by "ionic trapping" reagents arising from the interception of the first intermediate of the system supports the presence of a high valent VFe-C species. Mechanistic studies suggest a possible pathway operating via an Fe-centered ligand coupling. In addition, the production of alkyl chlorides and alkyl bromides could also be achieved employing this system in the presence of halogenating reagents such as CCl4 and BrCCl3.
- Barton, Derek H. R.,Beviere, Stephane D.,Chavasiri, Warinthorn
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- The functionalization of saturated hydrocarbons. Part 24. The use of tert-butyl hydroperoxide: GoAggIV and GoAggV
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The use of tert-butyl hydroperoxide as an oxidant in Gif-type systems (GoAggIV and GoAgfV) catalyzed by various Fe(III) species is examined. Regioselectivity studids of these systems have revealed several characteristics similar to those observed for other prdviously reported Gif-type reactions. A common rdaction pathway for the GoAggIV and GoAggV oxidation systems and other Gif-type reactions (from alkane via alkyl hydroperoxide to ketone or alcohol) is seen.
- Barton, Derek H. R.,Chavasiri, Warinthorn
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- Comments on An Article by Francesco Minisci and Francesca Fontana.
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Evidence is summarized to show that the least aspects of Gif chemistry do not involve Fenton-type radical chemistry.
- Barton, Derek H. R.,Hill, David R.
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p. 1431 - 1434
(2007/10/02)
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- Cobalt(II)-Porphyrin Catalyzed Selective Functionalization of Alkanes with sulfurylchloride: A Remarkable Substituent Effect
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Cobalt(II)-porphyrin complex 1 and 2 catalyses the chlorination and sulfochlorination respectively of n-alkanes and cycloalkanes with sulfuryl chloride in benzene.The p-substituent of the benzene ring in the porphyrin complex 1 and 2 shows a remarkable chemoselectivity in these reactions.
- Khanna, Vibha,Tamilselvan, Pitchiah,Kalra, Swinder Jeet Singh,Iqbal, Javed
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p. 5935 - 5938
(2007/10/02)
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- New Alkane Functionalization Reactions Based on Gif-Type Chemistry in the Presence of Alkali Metal Salts.
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Cycloalkanes are transformed into monosubstituted cycloalkyl derivatives (chloride, azide, cyanide, thiocyanate, dicycloalkyl disulfide, or nitroalkane) in mostly good efficiencies by treatment with tert-butyl hydroperoxide in pyridine/acetic acid containing Fe(NO3)3*9H2O, in the presence of alkali metal salts (LiCl, NaN3, CN, NaSCN, Na2S, or NaNO2, respectively).In comparison, ionic trapping with Cu(OAc)2 gave efficient trapping with chloride ion, very inefficient capture of thiocyanate, and a significant difference in reactivity towards azide ion.
- Barton, Derek H. R.,Beviere, Stephane D.,Chavasiri, Warinthorn,Doller, Dario,Hu, Bin
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p. 1871 - 1874
(2007/10/02)
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- The Effect of Triphenylphosphine in the GoAgg(II) System.
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The usual formation of ketone and alcohol under GoAgg(II) conditions can be totally replaced by the formation of the corresponding mono-alkyl substituted derivatives by addition of PPh3 and alkali metal salts.
- Barton, Derek H. R.,Beviere, Stephane D.
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p. 5689 - 5692
(2007/10/02)
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- HYDROCHLORINATION OF UNSATURATED COMPOUNDS BY THE ACTION OF CH2Cl2 OR CHCl3 AND RHODIUM COMPLEXES
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A new method has been developed for the catalytic hydrochlorination of olefins and acetylenes in the presence of Rh complexes by means of HCl generated in situ from CH2Cl2 and CHCl3 under the reaction conditions.The reaction was studied using the hydrochlorination of propylene, 1-hexene, 1-nonene, vinylcyclopropane, 1,1-dicyclopropylethylene, cyclohexene, cyclooctene, norbornene, and 1,5-cyclooctadiene as examples.
- Khusnutdinov, R. I.,Shchadneva, N. A.,Dzhemilev, U. M.,Tolstikov, G. A.
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p. 1213 - 1217
(2007/10/02)
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- Reactions of Difluoridichloromethane with Hydrocarbons
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The reaction of difluoridichloromethane with different hydrocarbons between 150 deg C and 250 deg C yields the CFCl2-substituted hydrocarbons.Beside it the corresponding chlorides are formed.For the hydrocarbons studied the following sequence of reactivity against difluordichloromethane was found: n-paraffins isoparaffins ca. cycloparaffins alkylaromatics olefines.
- Schmidt, H.,Burtzlaff, Ch.,Masuhr, H.',Ohl, J.,Pehle, W.,et al.
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p. 751 - 760
(2007/10/02)
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