- Experimental and theoretical studies of a greener catalytic system for saturated hydrocarbon chlorination composed by trichloroisocyanuric acid and a copper(II) compound
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We are describing herein a new environmentally friendly catalytic system able to convert cyclohexane to chlorocyclohexane with 100% selectivity. The method was also applied to the chlorination of n-hexane and adamantane. The catalytic system employs thichloroisocyanuric acid (TCCA) as halogenating agent and a mononuclear copper(II) complex [Cu(BPAH)(H2O)](ClO4)2, 1, as catalyst (BPAH = 1,4-bis(propanamide)homopiperazine), whose molecular structure was solved by monocrystal X-ray diffraction. For cyclohexane, at a ratio catalyst:substrate:TCCA of 1:1000:333, the system reached a conversion of 32.0 ± 1% at 25 °C and 44.7 ± 0.4% at 50 °C, with 100% selectivity for chlorocyclohexane. With n-hexane, a similar conversion was observed at 50 °C, resulting in mixture of monochlorides. Employing adamantane as substrate, the isomers 1-chloroadamantane and 2-chloroadamante were preferentially formed, together with traces of dichloroadamantane. EPR and ESI-(+)-MS analyses indicate the formation of a Cu-hypochlorite intermediate species, which is supported by theoretical calculations.
- Melo, Isis L.,Lube, Leonardo M.,Neves, Eduardo S.,Terra, Wagner S.,Fernandes, Christiane,Matos, Carlos R.R.,Franco, Roberto W.A.,Resende, Jackson A.L.C.,Valente, Daniel C.A.,Horta, Bruno A.C.,Cardozo, Thiago M.,Horn, Adolfo
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- 19F NMR of linear N,N-difluoroaminoalkanes
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Whereas most N,N-difluoroaminoalkanes exhibit a single 19F resonance at about +50 ppm, the tri-component mixtures of both N,N-difluoroaminopentanes and N,N-difluoroaminohexanes exhibited a more complex pattern. The individual 1-N,N-difluoroamino-, 2-N,N-difluoroamino- and 3-N,N-difluoroaminopentanes have been synthesized and their separated resonances are reported.
- Belter, Randolph K.
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- Practical and Selective sp3 C?H Bond Chlorination via Aminium Radicals
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The introduction of chlorine atoms into organic molecules is fundamental to the manufacture of industrial chemicals, the elaboration of advanced synthetic intermediates and also the fine-tuning of physicochemical and biological properties of drugs, agrochemicals and polymers. We report here a general and practical photochemical strategy enabling the site-selective chlorination of sp3 C?H bonds. This process exploits the ability of protonated N-chloroamines to serve as aminium radical precursors and also radical chlorinating agents. Upon photochemical initiation, an efficient radical-chain propagation is established allowing the functionalization of a broad range of substrates due to the large number of compatible functionalities. The ability to synergistically maximize both polar and steric effects in the H-atom transfer transition state through appropriate selection of the aminium radical has provided the highest known selectivity in radical sp3 C?H chlorination.
- McMillan, Alastair J.,Sieńkowska, Martyna,Di Lorenzo, Piero,Gransbury, Gemma K.,Chilton, Nicholas F.,Salamone, Michela,Ruffoni, Alessandro,Bietti, Massimo,Leonori, Daniele
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supporting information
p. 7132 - 7139
(2021/03/03)
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- Reagent-dictated site selectivity in intermolecular aliphatic C-H functionalizations using nitrogen-centered radicals
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The site selectivities of intermolecular, aliphatic C-H bond functionalizations are central to the value of these transformations. While the scope of these reactions continues to expand, the site selectivities remain largely dictated by the inherent reactivity of the substrate C-H bonds. Herein, we introduce reagent-dictated site selectivity to intermolecular aliphatic C-H functionalizations using nitrogen-centered amidyl radicals. Simple modifications of the amide lead to high levels of site selectivity in intermolecular C-H functionalizations across a range of simple and complex substrates. DFT calculations demonstrate that the steric demand of the reacting nitrogen-centered radical is heavily affected by the substitution pattern of the starting amide. Optimization of transition state structures consistently indicated higher reagent-dictated steric selectivities using more hindered amides, consistent with experimental results.
- Carestia, Anthony M.,Ravelli, Davide,Alexanian, Erik J.
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p. 5360 - 5365
(2018/06/27)
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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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- 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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- 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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- Site-Selective Aliphatic C-H Chlorination Using N-Chloroamides Enables a Synthesis of Chlorolissoclimide
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Methods for the practical, intermolecular functionalization of aliphatic C-H bonds remain a paramount goal of organic synthesis. Free radical alkane chlorination is an important industrial process for the production of small molecule chloroalkanes from simple hydrocarbons, yet applications to fine chemical synthesis are rare. Herein, we report a site-selective chlorination of aliphatic C-H bonds using readily available N-chloroamides and apply this transformation to a synthesis of chlorolissoclimide, a potently cytotoxic labdane diterpenoid. These reactions deliver alkyl chlorides in useful chemical yields with substrate as the limiting reagent. Notably, this approach tolerates substrate unsaturation that normally poses major challenges in chemoselective, aliphatic C-H functionalization. The sterically and electronically dictated site selectivities of the C-H chlorination are among the most selective alkane functionalizations known, providing a unique tool for chemical synthesis. The short synthesis of chlorolissoclimide features a high yielding, gram-scale radical C-H chlorination of sclareolide and a three-step/two-pot process for the introduction of the β-hydroxysuccinimide that is salient to all the lissoclimides and haterumaimides. Preliminary assays indicate that chlorolissoclimide and analogues are moderately active against aggressive melanoma and prostate cancer cell lines.
- Quinn, Ryan K.,K?nst, Zef A.,Michalak, Sharon E.,Schmidt, Yvonne,Szklarski, Anne R.,Flores, Alex R.,Nam, Sangkil,Horne, David A.,Vanderwal, Christopher D.,Alexanian, Erik J.
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supporting information
p. 696 - 702
(2016/02/03)
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- 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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p. 10656 - 10666
(2015/11/27)
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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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- A facile synthesis of racemic 4-ethyl fatty acids
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The synthesis of racemic 4-ethyl fatty acids is reported. A Grignard reagent was first prepared by 3-chloroalkane reacting with magnesium and then 4-ethyl fatty acid methyl esters were synthesised by coupling the Grignard reagent with methyl 3-bromopropionate in the presence of the catalyst Li 2CuCl4. The 4-ethyl fatty acid methyl esters were saponified and then acidified to give the 4-ethyl fatty acids. The syntheses of 4-ethylhexanoic acid, 4-ethylheptanoic acid, 4-ethyloctanoic acid, 4-ethylnonaoic acid and 4-ethyl decanoic acid are described. The structures of the 4-ethyl fatty acid methyl esters and 4-ethyl fatty acids were confirmed by 1H NMR, 13C NMR and HRMS.
- Liu, Yu-Ping,Guan, Wei,Yin, De-Cai,Tian, Hong-Yu,Sun, Bao-Guo
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p. 492 - 494
(2012/10/29)
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- Process to convert alkanes into primary alcohols
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This invention provides a process to convert alkanes to primary alcohols of the same carbon number. Carbon numbers of particular interest are C8 to C18. The process comprises the steps of: a) halogenating a linear or branched (or mixture of linear and branched) alkane to produce a mixture of primary mono-haloalkanes, internal mono-haloalkanes, unreacted alkanes, hydrogen halide, and possibly multi-haloalkanes in the presence of a catalyst and/or by heating the reaction mixture; b) separating the hydrogen halide from the mixture and optionally neutralizing it with a metal oxide to produce a partially halogenated metal oxide and/or metal halide which may be regenerated; c) separating the primary mono-haloalkanes from the mixture; d) reacting the separated primary mono-haloalkanes in a reactor with a metal oxide or combination of metal oxides and water to convert the aforesaid primary mono-haloalkane to a mixture of products that contains primary alcohols, unconverted primary mono-haloalkanes, and possibly other reaction products, and a partially halogenated metal oxide and/or metal halide which may be regenerated; e) regenerating the partially halogenated metal oxide and/or metal halide to halogen (such as Cl2) and/or acid and a metal oxide for recycle by reaction with air or oxygen; and f) removing the unreacted primary mono-haloalkane from the reaction mixture and then purifying the primary alcohol.
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Page/Page column 4
(2008/06/13)
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- Process to convert linear alkanes into alpha olefins
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This invention provides for a process to convert branched or linear alkanes to branched or linear alpha olefins (AO) of the same carbon number. The process comprises the steps of: a) halogenating linear alkanes, branched alkanes, or a mixture of linear and branched alkane to produce a mixture containing primary mono-haloalkanes and hydrogen halide; b) separating the hydrogen halide from the mixture and optionally neutralizing it with a metal oxide to produce a partially halogenated metal oxide and/or metal halide which may be regenerated; c) separating the primary mono-haloalkanes from the mixture; d) reacting the separated primary mono-haloalkanes with a metal oxide to produce a mixture of products that contains alpha olefins, unconverted primary mono-haloalkanes, possibly other reaction products, and a partially halogenated metal oxide and/or metal halide which may be regenerated; e) regenerating the partially halogenated metal oxide and/or metal halide to halogen and/or acid and a metal oxide (such as Cl2) for recycle by reaction with air or oxygen ; and f) removing the unreacted primary mono-haloalkane from the reaction mixture and then purifying the alpha olefin.
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Page/Page column 4
(2008/06/13)
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- Reactivity of bismuth(III) halides towards alcohols. A tentative to mechanistic investigation
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The reactivity of bismuth(III) halides (BiX3; X=Cl, Br and I) towards a series of alcohols has been investigated. Three different reactions have been studied, namely: halogenation, dehydration and etherification. The behaviour of these bismuth derivatives was found to depend on the nature of the halide bonded to the bismuth atom. Their reactivities can be interpreted on the basis of the Hard and Soft Acids and Bases (HSAB) principle. A mechanism is proposed which involves the formation of a complex of the alcohol with Bi(III).
- Keramane, El Mehdi,Boyer, Bernard,Roque, Jean-Pierre
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p. 1909 - 1916
(2007/10/03)
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- Preparative catalytic chlorination of adamantane, cyclohexane, and hexane in the system tetrachloromethane-MX2(PPh3)2 (MX2 = PdBr2, PtCl2)-acetonitrile-potassium carbonate
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Heating of saturated hydrocarbons RH (cyclohexane, adamantane, and hexane) with tetrachloromethane in the presence of acetonitrile, potassium carbonate, and catalytic amounts of dihalide triphenylphosphine complexes of palladium(II) or platinum(II), MX2(PPh)2 (MX2 = PdBr2, PtCi2), for 6-8 h at 120°C yields monochlorinated derivatives of the respective hydrocarbons in 30-55% yield. Benzene, toluene, ethylbenzene, and tetramethylsilane show low reactivity under the conditions adopted for the reaction. Relative reactivity of various bond types C-H of alkanes is in agreement with the well known sequence: tertiary > secondary > primary. A scheme is proposed assuming trichloromethyl radicals as active species, and the catalyst function consists in activating C-C1 bond of the tetrachloromethane.
- Vedernikov,Sayakhov,Zazybin,Solomonov
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p. 812 - 815
(2007/10/03)
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- New Catalytic System for Activation of Alkane and Arene C-H Bonds on the Basis of Platinum(II) Complexes and Tetrachloromethane
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Alkanes and alkylarencs RH (cyclohexane, n-hexane, toluene) in a mixture with CCl4 and MeCN (1:1:1, by volume), at temperatures of 110°C and higher, in the presence of platinum complexes of the formula cis-PtX2(L)2 (X = Cl, Ph, L = PPh3; X = Cl, L = MeCN), react to form chloroform and chloride RCl. Catalytic activity decreases in the order PtPh2(PPh3)2 (3.9) > PtCl2(PPh3)2 (1.0) > PtCl2(MeCN)2 (0.24). In the case of n-hexane, C-H bonds at the secondary carbon atoms are by a factor of 11 more active than those at the primary atom, and in the case of toluene, benzyl chloride is the main reaction product (99%). The reaction is first-order in cyclohexane, metal complex, and tetrachloromethane. The chlorination of toluene is zero-order in hydrocarbon. The results of kinetic studies permit to conclude that the role of the catalyst is to activate the tetrachloromethane C-Cl bonds by an oxidative addition scheme.
- Vedernikov,Zazybin,Borisoglebskii,Solomonov
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p. 1922 - 1924
(2007/10/03)
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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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- 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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p. 147 - 162
(2007/10/02)
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- Carbon-13 Nuclear Magnetic Resonance of Mono- and Di-chloro-hexanes and Mono- and Di-chloro-heptanes. Assignment of Configurations
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Carbon-13 NMR spectra of mono- and dichloro-hexanes and mono- and dichloro-heptanes are reported.Substituent effects for α, β and γ positions are presented.Differences between the 13C chemical shifts of diastereoisomers are observed in the cases of 2,4- and 2,5-dichlorohexanes and 2,4-, 2,5- and 3,5-dichloroheptanes.
- Nouguier, R.,Surzur, J.-M.,Virgili, A.
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p. 155 - 157
(2007/10/02)
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- Selectivity in the Halogenation of Hexane by Tertiary Aminium Radicals from the Photodecomposition of N-Halogenoammonium Perchlorates
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The photochlorination of hexane with tertiary N-chloroammonium perchlorates in trifluoroacetic acid gives monochlorohexanes in high yield and with a striking preference for the 2-isomer.It is shown that free-radical chains are involved in which hydrogen-atom abstraction is by tertiary aminium radicals.The marked preference for 2- compared with 3-chlorination is attributed mainly to the bulky aminium radical attacking the relatively more accessible 2-position; an alternative explanation involving a reversible hydrogen-atom abstraction is ruled out.The magnitude of the primary deuterium kinetic isotope effect in these photochlorinations gives information about the dependence of the extent of C-H bond breakage in the transition state on the structure of the abstracting aminium radical.
- Fuller, Steven E.,Smith, John R. Lindsay,Norman, Richard O. C.,Higgins, Raymond
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p. 545 - 552
(2007/10/02)
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