- New Alkane Functionalization Reactions Based on Gif-Type Chemistry in the Presence of Alkali Metal Salts.
-
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
-
-
Read Online
- Amavadine as a catalyst for the peroxidative halogenation, hydroxylation and oxygenation of alkanes and benzene
-
Synthetic amavadine models, [V(HIDPA)2]2- and [V(HIDA)2]2- [where HIDPA and HIDA stand for the basic forms of 2,2'-(hydroxyimino)dipropionic and 2,2'-(hydroxyimino)diacetic acid, respectively], exhibit haloperoxidase- or peroxidase-type activities, and act as catalysts for the selective peroxidative monohalogenation, hydroxylation or oxo-functionalization of alkanes or aromatic compounds such as benzene and mesitylene at room temperature.
- Reis,Silva,Frausto da Silva,Pombeiro
-
-
Read Online
- Comparison of gif-type reactivity towards alkanes with standard radical reaction selectivity. Gif oxidation of n-butane and propane
-
A precise comparison has been made between radical bromination of a series of saturated hydrocarbons using BrCCl3 and the bromination of the same series with the same reagent under Gif-type (GoAggIII) conditions. The relative reactivities in the two series are completely different and confirm a difference in mechanism. Experiments with n-butane and with propane have shown that these gases react with the usual Gif selectivity to furnish 2-butanone and acetone respectively.
- Barton, Derek H. R.,Csuhai, Eva,Doller, Dario,Ozbalik, Nubar,Senglet, Nathalie
-
-
Read Online
- Free radical addition of cyclopentane and cyclohexane to halogeno derivatives of 1,2-difluoroethene
-
Free radical addition reactions between cyclopentane and cyclohexane and a range of difluoroalkenes, CF2=CXY (X, Y = H, F, Cl, Br) gave a series of adducts bearing difluoromethylene substituents, R-CF2-CXYH (R = c-C5H9 or c-C6H11), in reasonable yield even though telomerisation and halogen transfer (when X, Y = Cl, Br) can compete. Dehydrofluorination of the adducts gave several new polyhalogenated alkenes.
- Cooper, Julian A.,Copin, Elodie,Sandford, Graham
-
-
Read Online
- Facile Conversion of Alkenes into Alkyl Bromides via Reaction of Organoboranes with Bromine or Bromine Chloride
-
Organoboranes react with either bromine or bromine chloride in aqueous media to yield the corresponding alkyl bromides under surprisingly mild conditions.The reaction is ideal for the synthesis of functionally substituted organic bromides.Sodium bromide may be utilized as the bromine source via its in situ conversion to bromine chloride by using mild oxidizing agents.
- Kabalka, George W.,Sastry, Kunda A. R.,Hsu, Henry C.,Hylarides, Mark D.
-
-
Read Online
- Studies on the bromination of saturated hydrocarbons under GoAggIII conditions
-
The bromination reaction of saturated hydrocarbons under GoAggIII conditons (FeCl3.6H2O picolinic acid, H2O2 in pyridine/acetic acid) and under radical chain conditions (dibenzoyl peroxide in pyridine/acetic acid or initiation by UV light) are compared. Differences in the selectivity and kinetic behavior for a series of polyhaloalkanes are in agreement with a non-radical mechanism for GoAggIII bromination. Comparison of the kinetic order of reactivity for a series of polyhaloalkanes under chain radical conditions and under GoAggIII conditions is in agreement with a non-radical reaction pathway for the Gif-type bromination reaction.
- Barton, Derek H. R.,Csuhai, Eva,Doller, Dario
-
-
Read Online
- Mechanistic elucidation of C-H oxidation by electron rich non-heme iron(IV)-oxo at room temperature
-
Non-heme iron(iv)-oxo species form iron(iii) intermediates during hydrogen atom abstraction (HAA) from the C-H bond. While synthesizing a room temperature stable, electron rich, non-heme iron(iv)-oxo compound, we obtained iron(iii)-hydroxide, iron(iii)-alkoxide and hydroxylated-substrate-bound iron(ii) as the detectable intermediates. The present study revealed that a radical rebound pathway was operative for benzylic C-H oxidation of ethylbenzene and cumene. A dissociative pathway for cyclohexane oxidation was established based on UV-vis and radical trap experiments. Interestingly, experimental evidence including O-18 labeling and mechanistic study suggested an electron transfer mechanism to be operative during C-H oxidation of alcohols (e.g. benzyl alcohol and cyclobutanol). The present report, therefore, unveils non-heme iron(iv)-oxo promoted substrate-dependent C-H oxidation pathways which are of synthetic as well as biological significance.
- Rana, Sujoy,Dey, Aniruddha,Maiti, Debabrata
-
-
Read Online
- Mechanism of Hydroxylation of Alkanes by Dimethyldioxirane. A Radical-Clock Study
-
The oxidation of 2-cyclopropylpropane by dimethyldioxirane (DMD) to 2-cyclopropylpropan-2-ol is not a free-radical chain reaction.It is suggested the free-radical chain observed by Minisci et al. when alkane/DMD reactions were carried out in the presence of CCl3Br involves H-atom abstraction from the alkane by Cl3COO. (in air) and by Me2C(O.)OCCl3 as well as by the Cl3C. radical.
- Vanni, Raffaella,Garden, Simon J.,Banks, Jeffrey T.,Ingold, Keith U.
-
-
Read Online
- Halogen Exchange Reaction of Aliphatic Fluorine Compounds with Organic Halides as Halogen Source
-
The halogen exchange reaction of aliphatic fluorine compounds with organic halides as the halogen source was achieved. Treatment of alkyl fluorides (primary, secondary, or tertiary fluorides) with a catalytic amount of titanocene dihalides, trialkyl aluminum, and polyhalomethanes (chloro or bromo methanes) as the halogen source gave the corresponding alkyl halides in excellent yields under mild conditions. In the case of a fluorine/iodine exchange, no titanocene catalyst is needed. Only C-F bonds are selectively activated under these conditions, whereas alkyl chlorides, bromides, and iodides are tolerant to these reactions.
- Mizukami, Yuki,Song, Zhiyi,Takahashi, Tamotsu
-
-
Read Online
- The Reaction of Bromine with Cyclohexene in Carbon Tetrachloride. Part 2. Reactions in the Presence of Added Hydrogen Bromide, and of Imides, and in the Absence of Additives
-
The addition of bromine to cyclohexene in carbon tetrachloride containing added hydrogen bromide takes place rapidly, and is of first order in each of these species.When bromine is added to cyclohexene in solutions containing succinimide or phthalimide, the addition reaction follows an expression of order 1.5 in bromine and 0.5 in the imide.When no other component is present, the addition of bromine to cyclohexene is extremely sensitive to unintentional additives, but is usually of order 1.5 in bromine and of small positive order in water.We suggest reasonable reaction mechanisms for these processes, involving species stoicheiometrically equivalent to HBr3 and HBr5, and discuss their applicability to the second, fast phase of the scavenged reactions described in Part 1.
- Hart, Lionel S.,Whiting, Mark C.
-
-
Read Online
- Catalytic Bromide and Iodide Exchange of Alkyl Chlorides with HBr and HI
-
The need to develop efficient methods for the conversion of the generally cheaper, readily available alkyl chlorides to the more reactive, synthetically useful alkyl bromides and iodides is addressed by the use of gaseous HBr and HI in the presence of a ferric halide catalyst.The simple catalytic procedure is especially applicable to secondary and tertiary alkyl chlorides as well as vicinal dichlorides at ambient temperatures in aprotic solvents such as dichloromethane and carbon tetrachloride.The unique role of the FeBr3 catalyst to effect a reversible exchange of bromide via carbenium intermediates is discussed.
- Yoon, K. B.,Kochi, J. K.
-
-
Read Online
- On the Mechanism of N-Bromosuccinimide Brominations. Bromination of Cyclohexane and Cyclopentane with N-Bromosuccinimide
-
The competitive N-bromosuccinimide (NBS) bromination of cyclopentane vs. cyclohexane was shown to proceed by a mechanism dominated by either a bromine atom chain, a succinimidyl chain, or a mixed chain.The dominance of each of the major chain-carrying processes depends upon the solvents used, to some degree upon the reactivity of the substrate, and upon the additives (molecular bromine or ethylene) used to moderate or enhance one or the other of the chain processes.No evidence was obtained, from studies of the NBS halogenation of the two substrates used, which required the intermediacy of an excited-state succinimidyl radical to explain the reactivities obtained.The observation that β-bromopropionyl isocyanate is produced under all of the reaction conditions precludes the requirement that brominations using the NBS-Br2 reagent proceed exclusively by a radical species whose reactions do not correlate with a ring-opening process.
- Tanner, Dennis D.,Ruo, Tomoki C.-S.,Takiguchi, Hideki,Guillaume, Andre,Reed, Darwin W.,et al.
-
-
Read Online
- A Novel Synthesis of Cyclohexanol Derivatives by the Catalytic Hydrogenation of Benzene with Acid Additives
-
The hydrogenation of benzene over a platinum group metal in the presence of various strong acids was carried out.Cyclohexanol derivatives (C6H11X, X=OH, OAc, Cl, Br) were found to be produced by the catalytic hydrogenation of benzene with acid additives.The following two sequences of adsorption strength were observed between platinum metals (adsorbent) and additive reagents (adsorbate): Ru >> Rh > Pd > Ir > Pt (I) and HI, HCOOH >> HBr > HCl >> AcOH, H2O. (II).When a weak adsorbate, such as acetic acid or water, was used as an additive reagent, ruthenium, the strongest adsorbent, exhibited the best selectivity.When hydrogen chloride, a strong adsorbate in the sequence (II), was used an additive reagent, palladium or rhodium, moderately strong adsorbent, exhibited excellent selectivity.By the reaction of 2 ml of benzene, 5 ml of 35percent HCl and 0.2 g of 5percent Pd/SiO2, under 10 atm-G (P atm-G=1.013(P+1)*105 Pa) hydrogen at 100 deg C for 20 h, 8,4percent of the yield of chlorocyclohexane was obtained at 64.2percent of the selectivity (13.1percent of the conversion of benzene).
- Yasuhara, Yutaka,Nishino, Masaki
-
-
Read Online
- Iron-catalyzed halogenation of alkanes: Modeling of nonheme halogenases by experiment and DFT calculations
-
When the dichloroiron(II) complex of the tetradentate bispidine ligand L = 3, 7-dimethyl-9-oxo-2, 4-bis(2pyridyl)-3, 7-diazabicyclo[3.3.1]nonane1, 5-dicarboxylate methyl ester is oxidized with H2O2, tBuOOH, or iodosylbenzene, the high-valent Fe=O complex efficiently oxidizes and halogenates cyclohexane. Kinetic D isotope effects and the preference for the abstraction of tertiary over secondary carbon-bound hydrogen atoms (quantified in the halogenation of adamantane) indicate that C-H activation is the rate-determining step. The efficiencies (yields in stoichiometric and turnover numbers in catalytic reactions), product ratios (alcohol vs. bromo- vs. chloroalkane), and kinetic isotope effects depend on the oxidant. These results suggest different pathways with different oxidants, and these may include iron(IV)- and iron(V)-oxo complexes as well as oxygen-based radicals.
- Comba, Peter,Wunderlich, Steffen
-
-
Read Online
- A hexanuclear mixed-valence oxovanadium(IV,V) complex as a highly efficient alkane oxidation catalyst
-
The new hexanuclear mixed-valence vanadium complex [V3O 3(OEt)(ashz)2(μ-OEt)]2 (1) with an N,O-donor ligand is reported. It acts as a highly efficient catalyst toward alkane oxidations by aqueous H2O2. Remarkably, high turnover numbers up to 25000 with product yields of up to 27% (based on alkane) stand for one of the most active systems for such reactions.
- Sutradhar, Manas,Kirillova, Marina V.,Guedes Da Silva, M. Fátima C.,Martins, Luísa M.D.R.S.,Pombeiro, Armando J. L.
-
-
Read Online
- Alkane functionalization at nonheme iron centers. stoichiometric transfer of metal-bound ligands to alkane
-
A series of [FeIIIX2L]+ complexes (L = TPA, tris(2-pyridylmethyl)amine, or NTB*, tris(N-ethylbenzimidazol-2-ylmethyl)amine; X = Br, Cl, or N3) has been synthesized and examined for their ability to activate alkyl hydroperoxides for the functionalization of alkanes at room temperature. The crystal structures of [FeCl2(TPA)]ClO4 (2) and [Fe2-OCl2(TPA)2] (ClO4)2 (6) were determined, while other complexes were characterized by their visible and NMR spectra. Treatment of the mononuclear complexes with a stoichiometric amount of alkyl hydroperoxide in the presence of cyclohexane affords halocyclohexane in good yield. The production of bromo- and azidocyclohexane was correlated with the disappearance of the characteristic LMCT bands of the mononuclear catalysts, which were converted into catalytically inactive (μ-oxo)diferric species. The yield of haloalkane increased to 100% based on complex when an excess of alkyl hydroperoxide was used, but it was not affected by the addition of excess halide. The formation of haloalkane was inhibited by the presence of dimethyl sulfide (forming DMSO), but was unaffected by the addition of 4-methyl-2,6-di-tert-butylphenol, suggesting the involvement of a two-electron oxidant in the reaction mechanism. The selectivities of the catalysts for cyclohexane and adamantane functionalization were significantly affected by the nature of the tripodal ligand and the bound halide but not by the alkyl group on the hydroperoxide. We thus propose the active species to be [O=Fe(L)(X)]2+, which may be related to the transient intermediate generated from the reaction of Fe2O(TPA)2(ClO4)4 with H2O2 (Leising et al. J. Am. Chem. Soc. 1991, 113, 3988-3990). In the proposed mechanism, [O=Fe(L)(X)]2+ abstracts hydrogen from the alkane and then transfers the bound halide to the incipient alkyl radical. Such an oxidative ligand transfer reaction has been proposed for the mechanism of thiazolidine ring formation in penicillin biosynthesis by the nonheme iron enzyme isopenicillin N synthase.
- Kojima, Takahiko,Leising, Randolph A.,Yan, Shiping,Que Jr., Lawrence
-
-
Read Online
- Mononuclear Nonheme High-Spin (S=2) versus Intermediate-Spin (S=1) Iron(IV)–Oxo Complexes in Oxidation Reactions
-
Mononuclear nonheme high-spin (S=2) iron(IV)–oxo species have been identified as the key intermediates responsible for the C?H bond activation of organic substrates in nonheme iron enzymatic reactions. Herein we report that the C?H bond activation of hydrocarbons by a synthetic mononuclear nonheme high-spin (S=2) iron(IV)–oxo complex occurs through an oxygen non-rebound mechanism, as previously demonstrated in the C?H bond activation by nonheme intermediate (S=1) iron(IV)–oxo complexes. We also report that C?H bond activation is preferred over C=C epoxidation in the oxidation of cyclohexene by the nonheme high-spin (HS) and intermediate-spin (IS) iron(IV)–oxo complexes, whereas the C=C double bond epoxidation becomes a preferred pathway in the oxidation of deuterated cyclohexene by the nonheme HS and IS iron(IV)–oxo complexes. In the epoxidation of styrene derivatives, the HS and IS iron(IV) oxo complexes are found to have similar electrophilic characters.
- Bae, Seong Hee,Seo, Mi Sook,Lee, Yong-Min,Cho, Kyung-Bin,Kim, Won-Suk,Nam, Wonwoo
-
-
Read Online
- Selective C-H activation of alipathic hydrocarbons under phase-transfer conditions
-
Bromination of alipathic hydrocarbons with NaOH/CBr4 under phase-transfer conditions selectively gives the tertiary bromide. In the absence of a tertiary C-H bond in the molecule, a secondary bond will be activated (see reaction equation). This conceptionally new system for alipathic C-H activation very likely relies on the initiation of single-electron transfer followed by a radical substitution with unusually high regioselectivity.
- Schreiner, Peter R.,Lauenstein, Oliver,Kolomitsyn, Igor V.,Nadi, Suad,Fokin, Andrey A.
-
-
Read Online
- The conversion of alcohols to halides using a filterable phosphine source
-
The conversion of primary and secondary alcohols to chlorides and bromides using 1,2-bis(diphenylphosphino)ethane (diphos) is described. Use of this reagent in lieu of the typical triphenylphosphine-carbontetrahalide complex provides a facile means of purifying the desired halide from the phosphine-oxide byproduct.
- Pollastri, Michael P.,Sagal, John F.,Chang, George
-
-
Read Online
- Copper(II) Complexes with Bulky N-Substituted Diethanolamines: High-Field Electron Paramagnetic Resonance, Magnetic, and Catalytic Studies in Oxidative Cyclohexane Amidation
-
The novel coordination compounds [Cu2(HtBuDea)2(OAc)2] (1) and [Cu2(HnBuDea)2Cl2]·nH2O (2) have been prepared through the reaction of the respective copper(II) salts with N-tert-butyldiethanolamine (H2tBuDea, for 1) or N-butyldiethanolamine (H2nBuDea, for 2) in methanol solution. Crystallographic analysis reveals that, in spite of the common binuclear {Cu2(μ-O)2} core, the supramolecular structures of the complexes are drastically different. In 1 binuclear molecules are linked together by H-bonds into 1D chains, while in 2 the neighboring pairs of binuclear molecules are H-bonded, forming tetranuclear aggregates. Variable-temperature (1.8-300 K) magnetic susceptibility measurements of 1 and 2 show a dominant antiferromagnetic behavior. Both complexes are also studied by HF-EPR spectroscopy. While the interaction between Cu(II) centers in 1 can be described by a single coupling constant J = 130.1(3) cm-1 (using H = JS1S2), the crystallographically different {Cu2(μ-O)2} pairs in 2 are expected exchange from ferro- to antiferromagnetic behavior (with J ranging from -32 to 110 cm-1, according to DFT calculations). Complexes 1 and 2 act as catalysts in the amidation of cyclohexane with benzamide, employing tBuOOtBu as oxidant. The maximum achieved conversion of benzamide (20%, after 24 h reaction time) was observed in the 1/tBuOOtBu system. In the cases of tBuOO(O)CPh or tBuOOH oxidants, no significant amidation product was observed, while for tBuOO(O)CPh, the oxidative dehydrogenation of cyclohexane occurred, giving cyclohexene, to afford the allylic ester (cyclohex-2-en-1-yl benzoate) as the main reaction product.
- Nesterova, Oksana V.,Nesterov, Dmytro S.,Jezierska, Julia,Pombeiro, Armando J. L.,Ozarowski, Andrew
-
-
Read Online
- Molybdenum blue nano-rings: An effective catalyst for the partial oxidation of cyclohexane
-
Molybdenum blue (MB), a multivalent molybdenum oxide with a nano-ring morphology is well-known in analytical chemistry but, to date it has been largely ignored in other applications. In the present work, MB has been characterized by STEM-HAADF imaging for the first time, showing the nano-ring morphology of this complex molybdenum oxide and the ordered super-molecular framework crystals that can result from the self-assembly of these MB nano-ring units. The potential of MB as an oxidation catalyst has also been investigated, where it is shown to have excellent catalytic activity and stability in the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone which are important intermediates in the production of nylon.
- Liu, Xi,Conte, Marco,Weng, Weihao,He, Qian,Jenkins, Robert L.,Watanabe, Masashi,Morgan, David J.,Knight, David W.,Murphy, Damien M.,Whiston, Keith,Kiely, Christopher J.,Hutchings, Graham J.
-
-
Read Online
- Free-Radicals in the Oxidation and Halogenation of Alkanes by Dimethyldioxirane: an Oxygen Rebound Mechanism
-
The oxidation of alkanes by dimethyldioxirane (DMD) in the presence of CBrCl3 provides strong evidence that free-radicals are involved in the reaction; enthalpic and polar effects and an "oxygen rebound" mechanism are suggested to explain the exceptional oxidation selectivity.
- Minisci, Francesco,Zhao, Lihua,Fontana, Francesca,Bravo, Anna
-
-
Read Online
- Mild one-pot preparation of glycosyl bromides
-
Mild one-pot protocols for the preparation of glycosyl bromides and alkyl bromides via in situ generation of HBr is reported here.
- Hunsen, Mo,Long, David A.,D'Ardenne, Christopher R.,Smith, Amanda L.
-
-
Read Online
- Cyclohexane oxidation with an O2–H2 mixture in the presence of a two-component Pt/C–heteropoly acid catalyst and ionic liquids
-
Approaches to increase the efficiency of Pt/C–heteropoly acid catalyst in a liquid-phase oxidation of cyclohexane using an O2–H2 mixture were studied. It was shown that small additives of ionic liquid (BMImBr, Bu4NBr, or Bu4NHSO4) significantly improve the catalytic effect of the Pt/C–H3PMo12O40–CH3CN system at 35°C, by slowing the rate of side reactions resulting in water formation, increasing the rate of oxygenate formation, and inhibiting their secondary oxidation reactions. The efficiency of H2 consumption increases from 2 to 18–25%, while the selectivity of cyclohexane conversion is 92–98%. The substitution of one or two Mo(VI) ions by V(V) in the structure of the heteropoly acid decreases these parameters. In the presence of Bu4NHSO4, a Pt/C catalyst can be used many times. During the reaction, the heteropoly acid present in the solution is in a reduced state under the action of the reaction medium and undergoes reversible redox transformations. The nature of the catalytic action of the studied system is explained from the viewpoint of the effect of ionic liquids on the properties of a Pt/C catalyst in activating O2, heteropoly molybdate chemistry, and the known mechanisms of the peroxide oxidation of hydrocarbons.
- Kuznetsova,Kuznetsova
-
-
Read Online
- Kinetic isotope effects for the C-H activation step in phase-transfer halogenations of alkanes
-
(equation presented) Within the scope of phase-transfer halogenations (Br and I) of alkanes, significant H/D kinetic isotope effects (KIE = 4-5) indicate that hydrogen abstraction is rate limiting. The excellent agreement of computed and experimentally determined H/D KIE as well as trapping experiments support the involvement of trihalomethyl radicals in the activation step.
- Lauenstein, Oliver,Fokin, Andrey A.,Schreiner, Peter R.
-
-
Read Online
- ORGANOBORANES FOR SYNTHESIS. 10. THE BASE-INDUCED REACTION OF BROMINE WITH ORGANOBORNES. A CONVENIENT PROCEDURE FOR THE CONVERSION OF ALKENES INTO ALKYL BROMIDES VIA HYDROBORATION
-
The reaction of trialkylboranes with bromine is greatly accelerated by base.Bromination in the presence of sodium hydroxide provides alkyl bromide along with a large amount of the corresponding alcohol.The use of sodium methoxide as a base eliminates this undesirable side reaction and provides an improved yield of alkyl bromide.Consequently, hydroboration, followed by bromination in the presence of sodium methoxide, provides a convenient new procedure for the conversion of alkenes into alkyl bromides.The organoboranes, obtained via hydroboration of terminal alkenes, react with the utilization of all three alkyl groups attached to boron, providing nearly quantitative yields of alkyl bromides. This procedure also accommodates common organic functional groups, as demonstrated by the preparation of methyl 11-bromoundecanoate and 11-bromoundecyl acetate from the corresponding functionally substituted alkenes.Under these conditions, secondary and bulky primary alkyl groups react more sluggishly.However, a procedure involving simultaneous addition of bromine and methanolic sodium methoxide provides improved results for such derivatives.Surprisingly, the base-induced bromination of tri-exo-nobornylborane results in an inversion of configuration at the reaction center to give predominantly endo-2-bromonorbornane.A mechanism is proposed to account for this remarkable inversion.
- Brown, Herbert C.,Lane, Clinton F.
-
-
Read Online
- A base-resistant metalloporphyrin metal-organic framework for C-H bond halogenation
-
A base-resistant porphyrin metal-organic framework (MOF), namely PCN-602 has been constructed with 12-connected LNi8(OH)4(H2O)2Pz12] (Pz = pyrazolate) cluster and a newly designed Pyrazolate-based porphyrin ligand, 5, 10, 15, 20-tetrakis(4-(pyrazolate-4-yl)-phenyl)porphyrin under the guidance of the reticular synthesis strategy. Besides its robustness in hydroxide solution, PCN-602 also shows excellent stability in aqueous solutions of F-, CO,2-, and PO43- ions. Interestingly, the Mn3+-porphyrinic PCN-602, as a recyclable MOF catalyst, presents high catalytic activity for the C-H bond halogenation reaction in a basic system, significantly outperforming its homogeneous counterpart. For the first time, a porphyrinic MOF was thus used as an efficient catalyst in a basic solution with coordinating anions, to the best of our knowledge.
- Lv, Xiu-Liang,Wang, Kecheng,Wang, Bin,Su, Jie,Zou, Xiaodong,Xie, Yabo,Li, Jian-Rong,Zhou, Hong-Cai
-
-
Read Online
- Metal-free and copper-promoted single-pot hydrocarboxylation of cycloalkanes to carboxylic acids in aqueous medium
-
A simple and effective method for the transformation, under mild conditions and in aqueous medium, of various cycloalkanes (cyclopentane, cyclohexane, methylcyclohexane, cis- and trans-1,2dimethylcyclohexane, cycloheptane, cyclooctane and adamantane) into the corresponding cycloalkanecarboxylic acids bearing one more carbon atom, is achieved. This method is characterized by a singlepot, low-temperature hydrocarboxylation reaction of the cycloalkane with carbon monoxide, water and potassium peroxodisulfate in water/acetonitrile medium, proceeding either in the absence or in the presence of a metal promoter. The influence of various reaction parameters, such as type and amount of metal promoter, solvent composition, temperature, time, carbon monoxide pressure, oxidant and cycloalkane, is investigated, leading to an optimization of the cyclohexane and cyclopentane carboxylations. The highest efficiency is observed in the systems promoted by a tetracopper(II) triethanolaminate-de rived complex, which also shows different bond and stereoselectivity parameters (compared to the metalfree systems) in the carboxylations of methylcyclohexane and stereoisomeric 1,2-dimethylcyclohexanes. A free radical mechanism is proposed for the carboxylation of cyclohexane as a model substrate, involving the formation of an acyl radical, its oxidation and consequent hydroxylation by water. Relevant features of the present hydrocarboxylation method, besides the operation in aqueous medium, include the exceptional metal-free and acid-solvent-free reaction conditions, a rare hydroxylating role of water, substrate versatility, low temperatures (ca. 50°C) and a rather high efficiency (up to 72% carboxylic acid yields based on cycloalkane).
- Kirillova, Marina V.,Kirillov, Alexander M.,Pombeiro, Armando J. L.
-
-
Read Online
- Radical Cations of Phenoxazine and Dihydrophenazine Photoredox Catalysts and Their Role as Deactivators in Organocatalyzed Atom Transfer Radical Polymerization
-
Radical cations of photoredox catalysts used in organocatalyzed atom transfer radical polymerization (O-ATRP) have been synthesized and investigated to gain insight into deactivation in O-ATRP. The stability and reactivity of these compounds were studied in two solvents, N,N-dimethylacetamide and ethyl acetate, to identify possible side reactions in O-ATRP and to investigate the ability of these radical cations to deactivate alkyl radicals. A number of other factors that could influence deactivation in O-ATRP were also probed, such as ion pairing with the radical cations, radical cation oxidation potential, and halide oxidation potential. Ultimately, these studies enabled radical cations to be employed as reagents during O-ATRP to demonstrate improvements in polymerization control with increasing radical cation concentrations. In the polymerization of acrylates, this approach enabled superior molecular weight control, a decrease in polymer dispersity from 1.90 to 1.44, and an increase in initiator efficiency from 78 to 102%. This work highlights the importance of understanding the mechanism and side reactions of O-ATRP, as well as the importance of catalyst radical cations for successful O-ATRP.
- Corbin, Daniel A.,McCarthy, Blaine G.,Van De Lindt, Zach,Miyake, Garret M.
-
-
Read Online
- Liquid phase oxidation of cyclohexane using bimetallic Au-Pd/MgO catalysts This paper is dedicated to Professor Jacques Vedrine on the event of his 75th birthday.
-
A detailed study of the selective oxidation of cyclohexane has been performed using bimetallic gold-palladium catalysts supported on magnesium oxide. Mono-metallic supported gold or palladium catalysts show limited activity for cyclohexane oxidation. However, a significantly enhanced catalytic performance is observed when supported gold-palladium alloy catalysts are used for this particular reaction. This synergy is observed for alloys spanning a wide range of gold-to-palladium molar ratios. Mechanistic studies reveal a promotion effect that occurs from alloying palladium with gold on the supported catalyst, which significantly improves the homo-cleavage of the O-O bond in cyclohexyl hydroperoxide, an important intermediate species in cyclohexane oxidation.
- Liu, Xi,Conte, Marco,Sankar, Meenakshisundaram,He, Qian,Murphy, Damien M.,Morgan, David,Jenkins, Robert L.,Knight, David,Whiston, Keith,Kiely, Christopher J.,Hutchings, Graham J.
-
-
Read Online
- Selective oxidation of cyclohexane to cyclohexanol catalyzed by a μ-hydroxo diiron(II) complex and tert-butylhydroperoxide
-
A new μ-hydroxo diiron(II) complex [Fe2L(OH)]3+ obtained with a dinucleating macrocyclic ligand catalyzes the selective oxidation of cyclohexane into cyclohexanol (≈85%) using the controlled addition of tert-butylhydroperoxide.
- Vincent, Jean-Marc,Bearnais-Barbry, Stephane,Pierre, Celine,Verlhac, Jean-Baptiste
-
-
Read Online
- FUNCTIONALIZATION OF SATURATED HYDROCARBONS BY MEANS OF APROTIC SUPERACIDS. 1. IONIC BROMINATION OF ALKANES AND CYCLOALKANES
-
Aprotic organic superacids with the composition AcBr*2AlX3 (X = Cl, Br) are efficient catalysts (Cat) for the bromination of n-alkanes and cycloalkanes by molecular bromine.Under the given conditions, the reactions afford (predominantly or exclusively) monobromides in high yields.
- Akhrem, I. S.,Orlinkov, A. V.,Vitt, S. V.,Afanas'eva, L. V.,Vol'pin, M. E.
-
-
Read Online
- The functionalization of saturated hydrocarbons. Part 39. Further evidence for the role of the iron-carbon bond in Gif chemistry
-
The functionalization of saturated hydrocarbons utilizing the Gif oxidation system is considered to occur via an intermediate containing an Fe-C bond. Iodine and iodide ion have been found to capture efficiently the Fe-C bond to give the corresponding alkyl iodide in both the Fe(II)-Fe(IV) and Fe(III)-Fe(V) manifolds. This trapping of the Fe-C bond in both manifolds is shown to be non-radical in nature.
- Barton, Derek H.R.,Costas Salgueiro, Miquel,MacKinnon, John
-
-
Read Online
- Thiourea-Mediated Halogenation of Alcohols
-
The halogenation of alcohols under mild conditions expedited by the presence of substoichiometric amounts of thiourea additives is presented. The amount of thiourea added dictates the pathway of the reaction, which may diverge from the desired halogenation reaction toward oxidation of the alcohol, in the absence of thiourea, or toward starting material recovery when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups. Detailed electron paramagnetic resonance (EPR) studies, isotopic labeling, and other control experiments suggest a radical-based mechanism. The fact that the reaction is carried out at ambient conditions, uses ubiquitous and inexpensive reagents, boasts a wide scope, and can be made highly atom economic, makes this new methodology a very appealing option for this archetypical organic reaction.
- Mohite, Amar R.,Phatake, Ravindra S.,Dubey, Pooja,Agbaria, Mohamed,Shames, Alexander I.,Lemcoff, N. Gabriel,Reany, Ofer
-
supporting information
p. 12901 - 12911
(2020/11/26)
-
- Decarboxylative Bromination of Sterically Hindered Carboxylic Acids with Hypervalent Iodine(III) Reagents
-
Sterically hindered three-dimensional (3D) alkyl halides are promising precursors for various reactions; however, they are difficult to synthesize via conventional reactions. We present an efficient and practical method for decarboxylative bromination of sterically hindered 3D aliphatic carboxylic acids using commercially available (diacetoxyiodo)benzene and potassium bromide, one of the most stable and cheapest bromine sources in nature. The present method features a metal-free/Br2-free system, mild reaction conditions, one-pot operation under air at room temperature, wide functional group compatibility, and gram-scale synthetic capability. This highly efficient reaction cleanly converts a broad range of carboxylic acids, the most inexpensive and readily available sources of highly strained/naturally occurring/drug-related scaffolds, into the corresponding alkyl bromides in good to high yields.
- Kanazawa, Junichiro,Koyamada, Kenta,Miyamoto, Kazunori,Uchiyama, Masanobu,Watanabe, Ayumi
-
supporting information
p. 1328 - 1334
(2020/08/14)
-
- 1,2-Dibromotetrachloroethane: An efficient reagent for many transformations by modified Appel reaction
-
An efficient and facile method has been developed for the synthesis of alkyl bromides from various alcohols under mild conditions using a triphenylphosphine (PPh 3) /1,2-dibromotetrachloroethane (DBTCE) complex in excellent yields and very short time (5 min). This method can also be applied for the transformation of chiral alcohols to their corresponding bromides in very high enantiomeric excess. The PPh 3 /DBTCE complex is also successfully applied to ring-opening reactions of cyclic ethers in mild conditions. Esterification, amidation, and formation of acid anhydrides under very mild experimental conditions are also successfully accomplished by following a modification of the Appel reaction protocol in this work.
- Essiz, Sel?uk,Da?tan, Arif
-
p. 150 - 156
(2019/05/16)
-
- N -Hydroxyphthalimide/benzoquinone-catalyzed chlorination of hydrocarbon C-H bond using N -chlorosuccinimide
-
The direct chlorination of C-H bonds has received considerable attention in recent years. In this work, a metal-free protocol for hydrocarbon C-H bond chlorination with commercially available N-chlorosuccinimide (NCS) catalyzed by N-hydroxyphthalimide (NHPI) with 2,3-dicyano-5,6-dichlorobenzoquinone (DDQ) functioning as an external radical initiator is presented. Aliphatic and benzylic substituents and also heteroaromatic ones were found to be well tolerated. Both the experiments and theoretical analysis indicate that the reaction goes through a process wherein NHPI functions as a catalyst rather than as an initiator. On the other hand, the hydrogen abstraction of the C-H bond conducted by a PINO species rather than the highly reactive N-centered radicals rationalizes the high chemoselectivity of the monochlorination obtained by this protocol as the latter is reactive towards the C(sp3)-H bonds of the monochlorides. The present results could hold promise for further development of a nitroxy-radical system for the highly selective functionalization of the aliphatic and benzylic hydrocarbon C-H.
- Li, Zi-Hao,Fiser, Béla,Jiang, Biao-Lin,Li, Jian-Wei,Xu, Bao-Hua,Zhang, Suo-Jiang
-
supporting information
p. 3403 - 3408
(2019/04/01)
-
- Highly Reactive Manganese(IV)-Oxo Porphyrins Showing Temperature-Dependent Reversed Electronic Effect in C-H Bond Activation Reactions
-
We report that Mn(IV)-oxo porphyrin complexes, MnIV(O)(TMP) (1) and MnIV(O)(TDCPP) (2), are capable of activating the C-H bonds of hydrocarbons, including unactivated alkanes such as cyclohexane, via an oxygen non-rebound mechanism. Interestingly, 1 with an electron-rich porphyrin is more reactive than 2 with an electron-deficient porphyrin at a high temperature (e.g., 0 °C). However, at a low temperature (e.g., -40 °C), the reactivity of 1 and 2 is reversed, showing that 2 is more reactive than 1. To the best of our knowledge, the present study reports the first example of highly reactive Mn(IV)-oxo porphyrins and their temperature-dependent reactivity in C-H bond activation reactions.
- Guo, Mian,Seo, Mi Sook,Lee, Yong-Min,Fukuzumi, Shunichi,Nam, Wonwoo
-
supporting information
p. 12187 - 12191
(2019/08/20)
-
- Catalytic Bromination of Alkyl sp3C-H Bonds with KBr/Air under Visible Light
-
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
-
supporting information
p. 5264 - 5267
(2018/09/12)
-
- An efficient conversion of alcohols to alkyl bromides using pyridinium based ionic liquids: A green alternative to appel reaction
-
Pyridinium based ionic liquids namely 4-alkylpyridinium bromides were prepared and used for the conversion of alcohols to alkyl bromides in the presence of p-toluenesulphonic acid in the absence of volatile organic compounds. This solvent free procedure promises to be a much improved and environmentally benign alternative to the Appel reaction.
- Das, Pranab J.,Das, Jupitara,Das, Dimpee
-
p. 651 - 654
(2018/02/09)
-
- Aliphatic C-H Bond Halogenation by Iron(II)-α-Keto Acid Complexes and O2: Functional Mimicking of Nonheme Iron Halogenases
-
α-Ketoglutarate-dependent nonheme halogenases catalyze the halogenation of aliphatic C-H bonds in the biosynthesis pathway of many natural products. An iron(IV)-oxo-halo species has been established as the active oxidant in the halogenation reactions. With an objective to emulate the function of the nonheme halogenases, two iron(II)-α-keto acid complexes, [(phdpa)Fe(BF)Cl] (1) and [(1,4-tpbd)Fe2(BF)2Cl2] (2) (where phdpa = N,N-bis(2-pyridylmethyl)aniline, 1,4-tpbd = N,N,N′,N'-tetrakis(2-pyridylmethyl)benzene-1,4-diamine, and BF = benzoylformate), have been prepared. The iron complexes are capable of carrying out the oxidative halogenation of aliphatic C-H bonds using O2 as the terminal oxidant. Although the complexes are not selective toward C-H bond halogenation, they are the only examples of nonheme iron(II)-α-keto acid complexes mimicking the activity of nonheme halogenases. The dinuclear complex (2) exhibits enhanced reactivity toward C-H bond halogenation/hydroxylation.
- Jana, Rahul Dev,Sheet, Debobrata,Chatterjee, Sayanti,Paine, Tapan Kanti
-
p. 8769 - 8777
(2018/08/17)
-
- Highly selective halogenation of unactivated C(sp3)-H with NaX under co-catalysis of visible light and Ag@AgX
-
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
-
p. 4729 - 4737
(2018/10/23)
-
- Selective C-H halogenation over hydroxylation by non-heme iron(iv)-oxo
-
Non-heme iron based halogenase enzymes promote selective halogenation of the sp3-C-H bond through iron(iv)-oxo-halide active species. During halogenation, competitive hydroxylation can be prevented completely in enzymatic systems. However, synthetic iron(iv)-oxo-halide intermediates often result in a mixture of halogenation and hydroxylation products. In this report, we have developed a new synthetic strategy by employing non-heme iron based complexes for selective sp3-C-H halogenation by overriding hydroxylation. A room temperature stable, iron(iv)-oxo complex, [Fe(2PyN2Q)(O)]2+ was directed for hydrogen atom abstraction (HAA) from aliphatic substrates and the iron(ii)-halide [FeII(2PyN2Q)(X)]+ (X, halogen) was exploited in conjunction to deliver the halogen atom to the ensuing carbon centered radical. Despite iron(iv)-oxo being an effective promoter of hydroxylation of aliphatic substrates, the perfect interplay of HAA and halogen atom transfer in this work leads to the halogenation product selectively by diverting the hydroxylation pathway. Experimental studies outline the mechanistic details of the iron(iv)-oxo mediated halogenation reactions. A kinetic isotope study between PhCH3 and C6D5CD3 showed a value of 13.5 that supports the initial HAA step as the RDS during halogenation. Successful implementation of this new strategy led to the establishment of a functional mimic of non-heme halogenase enzymes with an excellent selectivity for halogenation over hydroxylation. Detailed theoretical studies based on density functional methods reveal how the small difference in the ligand design leads to a large difference in the electronic structure of the [Fe(2PyN2Q)(O)]2+ species. Both experimental and computational studies suggest that the halide rebound process of the cage escaped radical with iron(iii)-halide is energetically favorable compared to iron(iii)-hydroxide and it brings in selective formation of halogenation products over hydroxylation.
- Rana, Sujoy,Biswas, Jyoti Prasad,Sen, Asmita,Clémancey, Martin,Blondin, Geneviève,Latour, Jean-Marc,Rajaraman, Gopalan,Maiti, Debabrata
-
p. 7843 - 7858
(2018/10/31)
-
- Preparation method of alkane brominated material
-
The invention relates to a preparation method of an alkane brominated material. The preparation method comprises the following steps: adding alkane, a bromine-containing compound or elemental bromine,a catalyst and acid into a solvent; adding the solvent into a light-transmission reaction container under air or oxygen atmosphere; sealing; performing stirring reaction under constant pressure and light illumination conditions; then analyzing a nuclear magnetic yield, and performing extraction, drying, filtration, distillation under reduced pressure and column separation to obtain the alkane brominated material. Compared with the prior art, the preparation method disclosed by the invention has the advantages that by using low-cost and safe bromic salt as a bromine source, the air as an oxidizing agent and a nitrogen-containing reagent as the catalyst, reaction is carried out under the conditions of constant temperature and constant pressure, so that energy conservation and economy are realized, and the preparation method is convenient and safe to operate and is environmentally friendly.
- -
-
Paragraph 0034-0035; 0037-0038; 0040-0041
(2018/09/08)
-
- HBr–DMPU: The First Aprotic Organic Solution of Hydrogen Bromide
-
HBr and DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone) form a room-temperature-stable complex that provides a mild, effective, and selective hydrobrominating reagent toward alkynes, alkenes, and allenes. HBr–DMPU could also replace other halogenating reagents in the halo-Prins reaction, ether cleavage, and deoxy-bromination reactions.
- Li, Zhou,Ebule, Rene,Kostyo, Jessica,Hammond, Gerald B.,Xu, Bo
-
supporting information
p. 12739 - 12743
(2017/09/25)
-
- Preparation of manganese/Graphite oxide composite using permanganate and graphite: Application as catalyst in bromination of hydrocarbons
-
A highly efficient one-pot preparation of manganese/graphite oxide (MnOX/GO) composite from graphite and KMnO4 is described. Hummers preparation method of GO requires a stoichiometric amount of KMnO4, as a result, the method produces a large amount of reduced Mn species. The Mn residue generally is a waste, therefore, we envisioned converting it to value-Added materials. A MnOX/GO composite was prepared in one-pot by treating the unpurified GO with aqueous KOH. The composite was characterized by XRD, XAFS, SEM and TEM. Among various applications of the MnOX/GO composite, we applied it as a recyclable catalyst for bromination of saturated hydrocarbons, one of the most basic but important chemical transformations. The MnOX/GO composite is expected to be an efficient catalyst because of the high surface area and high accessibility of substrates derived from the 2- dimensional sheet structure. When the reaction of a saturated hydrocarbon and Br2 in the presence of catalytic MnOX/GO was performed under fluorescent light irradiation, a brominated product was formed in high yield in a short reaction time. GO could strongly bind with Mn to prevent elution to the liquid phase, enabling the high recyclability.
- Suzuki, Hideyuki,Nishina, Yuta
-
supporting information
p. 74 - 78
(2017/08/14)
-
- PROCESS FOR THE PREPARATION OF ORGANIC BROMIDES
-
The present invention provides a process for the preparation of organic bromides, by a radical bromodecarboxylation of carboxylic acids with a bromoisocyanurate.
- -
-
Paragraph 00166
(2017/07/28)
-
- A alkane halogenation method (by machine translation)
-
The invention relates to a cycloalkane of halogenation method, comprises the following steps: S1: taking inorganic hydrohalide salt M+ X- And the inorganic acid or organic acid, stirring to dissolve in water, containing the halide X- Aqueous solution; S2: light in the reactor will be put aqueous solution, add nanometer metal/semiconductor composite material photocatalyst, phase transfer catalyst and reaction substrate cycloalkane; S3: under the stirring condition, in the sunlight or 300W xenon lamp or LED light shifted to catalytic reaction; S4: reaction after the fluid is static set, filtering and recycling photocatalyst, separating and recovering the aqueous phase and then, drying the organic phase, and the dried organic phase rectification separation purification, to obtain the corresponding organic halogenated product. The present invention provides a method halide of the cycloalkanes, low cost, the apparatus is simple and easy to operate, high selectivity, easy separation, can be large-scale production, is a novel, environmental protection, high selectivity, low energy consumption of the new organic halide, viable green channels, with potential industrial application value. (by machine translation)
- -
-
Paragraph 0038; 0039
(2017/07/21)
-
- Modeling Non-Heme Iron Halogenases: High-Spin Oxoiron(IV)-Halide Complexes That Halogenate C-H Bonds
-
The non-heme iron halogenases CytC3 and SyrB2 catalyze C-H bond halogenation in the biosynthesis of some natural products via S = 2 oxoiron(IV)-halide intermediates. These oxidants abstract a hydrogen atom from a substrate C-H bond to generate an alkyl radical that reacts with the bound halide to form a C-X bond chemoselectively. The origin of this selectivity has been explored in biological systems but has not yet been investigated with synthetic models. Here we report the characterization of S = 2 [FeIV(O)(TQA)(Cl/Br)]+ (TQA = tris(quinolyl-2-methyl)amine) complexes that can preferentially halogenate cyclohexane. These are the first synthetic oxoiron(IV)-halide complexes that serve as spectroscopic and functional models for the halogenase intermediates. Interestingly, the nascent substrate radicals generated by these synthetic complexes are not as short-lived as those obtained from heme-based oxidants and can be intercepted by O2 to prevent halogenation, supporting an emerging notion that rapid rebound may not necessarily occur in non-heme oxoiron(IV) oxidations.
- Puri, Mayank,Biswas, Achintesh N.,Fan, Ruixi,Guo, Yisong,Que, Lawrence
-
p. 2484 - 2487
(2016/03/12)
-
- An efficient and selective method for the iodination and bromination of alcohols under mild conditions
-
A straightforward and effective procedure for the conversion of a variety of alcohols into the corresponding alkyl iodides and bromides is described using KX/P2O5 (X = I, Br). The reactions were easily carried out in acetonitrile under mild conditions. Using this method, the selective conversion of benzylic alcohols in the presence of aliphatic alcohols was achieved.
- Khazdooz, Leila,Zarei, Amin,Aghaei, Hamidreza,Azizi, Ghobad,Gheisari, Mohammad Mehdi
-
p. 168 - 171
(2015/12/30)
-
- Catalytic Access to Alkyl Bromides, Chlorides and Iodides via Visible Light-Promoted Decarboxylative Halogenation
-
Herein is reported the catalytic, visible light-promoted, decarboxylative halogenation (bromination, chlorination, and iodination) of aliphatic carboxylic acids. This operationally-simple reaction tolerates a range of functional groups, proceeds at room temperature, and is redox neutral. By employing an iridium photocatalyst in concert with a halogen atom source, the use of stoichiometric metals such as silver, mercury, thallium, and lead can be circumvented. This reaction grants access to valuable synthetic building blocks from the large pool of cheap, readily available carboxylic acids.
- Candish, Lisa,Standley, Eric A.,Gómez-Suárez, Adrián,Mukherjee, Satobhisha,Glorius, Frank
-
supporting information
p. 9971 - 9974
(2016/07/19)
-
- Ruthenium bipyridyl tethered porous organosilica: A versatile, durable and reusable heterogeneous photocatalyst
-
A versatile heterogeneous photocatalysis protocol was developed by using ruthenium bipyridyl tethered porous organosilica (Ru-POS). The versatility of the Ru-POS catalyst in organo-photocatalysis was explored by (i) oxidative aromatization of Hantzsch ester, (ii) reductive dehalogenation of alkyl halides, and (iii) functional group interconversion (FGI) of alcohols to alkyl halides. This journal is
- Jana, Avijit,Mondal, John,Borah, Parijat,Mondal, Sujan,Bhaumik, Asim,Zhao, Yanli
-
supporting information
p. 10746 - 10749
(2015/06/30)
-
- A novel route for the synthesis of alkanes from glycerol in a two step process using a Pd/SBA-15 catalyst
-
Glycerol is produced as a valuable by-product in the transesterification of fatty acids, but it cannot be used directly as a fuel additive. In this study, we developed a systematic conversion for glycerol, which proceeds via synthesizing the key intermediate, 1,2,3-tribromopropane and using the Suzuki coupling reaction to introduce the alkyl group. A series of Pd/SBA-15 catalysts with different wt% of Pd (10%, 15% and 20%) was prepared by a one step sol-gel method. The structure and composition of the catalysts were characterized by X-ray diffraction analysis (XRD), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectrometry (ICP-OES). The metallic state of dispersed palladium in SBA-15 is confirmed with X-ray photoelectron spectroscopy (XPS). Pd/SBA-15 with a Pd loading of 20 wt% shows good catalytic activity at 90 °C with methylboronic acid, allowing the complete conversion of 1,2,3-tribromopropane and 64% selectivity of 3-methylpentane. The optimized catalysts were also employed in coupling reactions between various alkylhalides and methylboronic acid, which obtained the desired product with an excellent selectivity. The catalyst can be successfully recycled five times. After the first cycle, we observed a drop in activity with 20% Pd/SBA-15, which was due to the leaching of palladium but in the later cycles, there was no significant decrease in activity.
- Udayakumar,Pandurangan
-
p. 78719 - 78727
(2015/10/05)
-
- Hydrogenation of arenes, nitroarenes, and alkenes catalyzed by rhodium nanoparticles supported on natural nanozeolite clinoptilolite
-
Abstract Nanozeolite clinoptilolite supported rhodium nanoparticles (Rh/NZ-CP) has been prepared and characterized by a variety of techniques, including XRD, BET, TEM, EDX, ICP-OES and XPS analysis. This nanomaterial contains 2 wt% Rh in the range of 5-20 nm metallic nanoparticles distributed on nanozeolite. The catalytic performance of Rh/NZ-CP was evaluated by the hydrogenation of arenes, nitroarenes, and alkenes under moderate reaction conditions. The prepared nanocatalyst can be facilely recovered and reused many times without significant decrease in activity and selectivity. The high catalytic activity, thermal stability and reusability, simple recovery and eco-friendly nature make present catalyst as a unique catalytic system, which is particularly attractive in green chemistry.
- Baghbanian, Seyed Meysam,Farhang, Maryam,Vahdat, Seyed Mohammad,Tajbakhsh, Mahmood
-
p. 128 - 136
(2015/07/15)
-
- Copper-catalyzed oxidative dehydrogenative carboxylation of unactivated alkanes to allylic esters via alkenes
-
We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV-vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C-H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C-H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper-carboxylate, copper-amidate, and copper-imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)-amidate > Cu(II)-imidate > Cu(II)-benzoate. Consistent with this trend, Cu(II)-amidates and Cu(II)-benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products.
- Tran, Ba L.,Driess, Matthias,Hartwig, John F.
-
supporting information
p. 17292 - 17301
(2015/02/02)
-
- Iron-catalyzed borylation of alkyl, allyl, and aryl halides: Isolation of an iron(I) boryl complex
-
Activation of B2pin2 with tBuLi facilitates the Fe-catalyzed borylation of alkyl, allyl, benzyl, and aryl halides via the formation of Li[B2pin2(tBu)] (1). The reaction of 1 with a representative iron phosphine precatalyst generates the unique iron(I) boryl complex [Fe(Bpin)(dpbz)2] (2).
- Bedford, Robin B.,Brenner, Peter B.,Carter, Emma,Gallagher, Timothy,Murphy, Damien M.,Pye, Dominic R.
-
supporting information
p. 5940 - 5943
(2015/01/08)
-
- Oxidative bromination of alkenes mediated with nitrite in ionic liquids
-
The oxidative bromination of C2-C8 alkenes with HBr-NaNO2-O2 in solutions of BMImBr, HMImBr or BMImBF 4 containing 16-28 wt% H2O was studied using volumetric method, GC-MS analysis, 14N NMR and UV-VIS spectroscopy. The optimal conditions to conduct the reaction at high selectivity for 1,2-dibromoalkanes in BMImBr were determined. The composition of ionic liquid affects the catalytic performance. Although in BMImBF4 the reaction runs with equal rate as in bromide ionic liquid, the fraction of bromohydrin in the reaction products increases to 20 %. Generated from NaNO2, NOx operated as a catalyst in the oxidation of Br- and was oxidized to catalytically inert NO3 - anions when complete conversion of HBr was attained. Graphical Abstract: Oxidative bromination of alkenes [Figure not available: see fulltext.]
- Kuznetsova, Lidia I.,Kuznetsova, Nina I.,Zudin, Vladimir N.,Utkin, Viktor A.,Trebushat, Dmitry V.,Fedotov, Martin A.,Larina, Tatyana V.
-
p. 1499 - 1506,8
(2014/11/08)
-
- Tribromoisocyanuric acid/triphenylphosphine: A new system for conversion of alcohols into alkyl bromides
-
An efficient and facile method has been developed for the conversion of alcohols into alkyl bromides under neutral conditions using tribromoisocyanuric acid and triphenylphosphine (molar ratio 1.0:0.7:2.0, alcohol/ tribromoisocyanuric acid/triphenylphosphine) in dichloromethane at room temperature. This method can be applied for the conversion of primary, secondary, benzylic and allylic alcohols, and their corresponding bromides are obtained in 67-82 percent yield. Tertiary alcohols do not react under these conditions.
- De Andrade, Vitor S.C.,De Mattos, Marcio C.S.
-
p. 975 - 979
(2014/06/24)
-
- Revisiting the bromination of c-h bonds with molecular bromine by using a photo-microflow system
-
The photobromination of C-H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous-flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition. Go with the (micro)flow: Photobromination of C-H bonds by using molecular bromine under microfluidic conditions has been investigated (see scheme). The continuous-flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated compounds with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition.
- Manabe, Yoshiyuki,Kitawaki, Yuriko,Nagasaki, Masahiro,Fukase, Koichi,Matsubara, Hiroshi,Hino, Yoshiko,Fukuyama, Takahide,Ryu, Ilhyong
-
supporting information
p. 12750 - 12753
(2015/03/30)
-
- Copper-catalyzed intermolecular amidation and imidation of unactivated alkanes
-
We report a set of rare copper-catalyzed reactions of alkanes with simple amides, sulfonamides, and imides (i.e., benzamides, tosylamides, carbamates, and phthalimide) to form the corresponding N-alkyl products. The reactions lead to functionalization at secondary C-H bonds over tertiary C-H bonds and even occur at primary C-H bonds. [(phen)Cu(phth)] (1-phth) and [(phen)Cu(phth)2] (1-phth2), which are potential intermediates in the reaction, have been isolated and fully characterized. The stoichiometric reactions of 1-phth and 1-phth2 with alkanes, alkyl radicals, and radical probes were investigated to elucidate the mechanism of the amidation. The catalytic and stoichiometric reactions require both copper and tBuOOtBu for the generation of N-alkyl product. Neither 1-phth nor 1-phth2 reacted with excess cyclohexane at 100 C without tBuOOtBu. However, the reactions of 1-phth and 1-phth2 with tBuOOtBu afforded N-cyclohexylphthalimide (Cy-phth), N-methylphthalimide, and tert-butoxycyclohexane (Cy-OtBu) in approximate ratios of 70:20:30, respectively. Reactions with radical traps support the intermediacy of a tert-butoxy radical, which forms an alkyl radical intermediate. The intermediacy of an alkyl radical was evidenced by the catalytic reaction of cyclohexane with benzamide in the presence of CBr4, which formed exclusively bromocyclohexane. Furthermore, stoichiometric reactions of [(phen)Cu(phth)2] with tBuOOtBu and (Ph(Me)2CO) 2 at 100 C without cyclohexane afforded N-methylphthalimide (Me-phth) from β-Me scission of the alkoxy radicals to form a methyl radical. Separate reactions of cyclohexane and d12-cyclohexane with benzamide showed that the turnover-limiting step in the catalytic reaction is the C-H cleavage of cyclohexane by a tert-butoxy radical. These mechanistic data imply that the tert-butoxy radical reacts with the C-H bonds of alkanes, and the subsequent alkyl radical combines with 1-phth2 to form the corresponding N-alkyl imide product.
- Tran, Ba L.,Li, Bijie,Driess, Matthias,Hartwig, John F.
-
supporting information
p. 2555 - 2563
(2014/03/21)
-
- Mechanistic insight into the hydroxylation of alkanes by a nonheme iron(V)-oxo complex
-
Hydroxylation of alkanes by a mononuclear nonheme iron(v)-oxo complex, [Fe(v)(O)(TAML)]-, is initiated by a rate-determining hydrogen atom (H-atom) abstraction, followed by an oxygen non-rebound process. Evidence for the H-atom abstraction-oxygen non-rebound mechanism is obtained experimentally and supported by DFT calculations. the Partner Organisations 2014.
- Kwon, Eunji,Cho, Kyung-Bin,Hong, Seungwoo,Nam, Wonwoo
-
supporting information
p. 5572 - 5575
(2014/05/20)
-
- Site-selective aliphatic C-H bromination using N -bromoamides and visible light
-
Transformations that selectively functionalize aliphatic C-H bonds hold significant promise to streamline complex molecule synthesis. Despite the potential for site-selective C-H functionalization, few intermolecular processes of preparative value exist. Herein, we report an approach to unactivated, aliphatic C-H bromination using readily available N-bromoamide reagents and visible light. These halogenations proceed in useful chemical yields, with substrate as the limiting reagent. The site selectivities of these radical-mediated C-H functionalizations are comparable (or superior) to the most selective intermolecular C-H functionalizations known. With the broad utility of alkyl bromides as synthetic intermediates, this convenient approach will find general use in chemical synthesis.
- Schmidt, Valerie A.,Quinn, Ryan K.,Brusoe, Andrew T.,Alexanian, Erik J.
-
supporting information
p. 14389 - 14392
(2014/12/10)
-
- Bromination of hydrocarbons with CBr4, initiated by light-emitting diode irradiation
-
The bromination of hydrocarbons with CBr4 as a bromine source, induced by light-emitting diode (LED) irradiation, has been developed. Monobromides were synthesized with high efficiency without the need for any additives, catalysts, heating, or inert conditions. Action and absorption spectra suggest that CBr4 absorbs light to give active species for the bromination. The generation of CHBr3 was confirmed by NMR spectroscopy and GC-MS spectrometry analysis, indicating that the present bromination involves the homolytic cleavage of a C-Br bond in CBr4 followed by radical abstraction of a hydrogen atom from a hydrocarbon.
- Nishina, Yuta,Ohtani, Bunsho,Kikushima, Kotaro
-
p. 1663 - 1667
(2013/10/22)
-
- Direct bromination of hydrocarbons catalyzed by Li2MnO 3 under oxygen and photo-irradiation conditions
-
A method for the direct bromination of hydrocarbons with Br2 using a ubiquitous and inexpensive catalyst is highly desirable. Herein, we report the selective mono-bromination of hydrocarbons in good yield using Li2MnO3 as a catalyst under irradiation with a fluorescent room light. This new catalyst can be recycled. The effect of light was investigated using action spectra, which revealed that the reaction occurred on the surface of the catalyst.
- Nishina, Yuta,Morita, Junya,Ohtani, Bunsho
-
p. 2158 - 2162
(2013/03/13)
-
- Introducing copper as catalyst for oxidative alkane dehydrogenation
-
The dehydrogenation of n-hexane and cycloalkanes giving n-hexene and cycloalkenes has been observed in the reaction of such hydrocarbons with hydrogen peroxide, in the presence of copper complexes bearing trispyrazolylborate ligands. This catalytic transformation provides the typical oxidation products (alcohol and ketones) with small amounts of the alkenes, a novel feature in this kind of oxidative processes. Experimental data exclude the participation of hydroxyl radicals derived from Fenton-like reaction mechanisms. DFT studies support a copper-oxo active species, which initiates the reaction by H abstraction. Spin crossover from the triplet to the singlet state, which is required to recover the catalyst, yields the major hydroxylation and minor dehydrogenation products. Further calculations suggested that the superoxo and hydroperoxo species are less reactive than the oxo. A complete mechanistic proposal in agreement with all experimental and computational data is proposed.
- Conde, Ana,Vilella, Laia,Balcells, David,Díaz-Requejo, M. Mar,Lledós, Agustí,Pérez, Pedro J.
-
p. 3887 - 3896
(2013/04/23)
-
- C-HALOGEN BOND FORMATION
-
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.
- -
-
Paragraph 0111-0118
(2013/03/26)
-
- Synthesis of silica bromide as heterogeneous reagent and its application to conversion of alcohols to alkyl bromides
-
Silica bromide as heterogeneous reagent is prepared from the reaction of silica gel with PBr3 as a nonhydroscopic, filterable, cheap, and stable yellowish powder that can be stored for months. The results show that the silica bromide is a suitable and efficient reagent for conversion of alcohols to alkyl bromides under mild conditions at room temperature. The easy availability of this reagent makes this simple procedure attractive and a practical alternative to the existing methods.
- Mohanazadeh, Farajollah,Sedrpoushan, Alireza,Zolfigol, Mohammad A.,Veisi, Hojat
-
p. 598 - 603,6
(2012/12/11)
-
- CuI controlled C-C and C-N bond formation of heteroaromatics through C(sp3)-H activation
-
A new method for C-C and C-N bond formation of heteroaromatics and C(sp3)-H alkanes was developed with high regioselectivity. The reaction occurred on C8 to give 8-cylcoakylpurines by C-C bond formation only promoted by tBuOOtBu, while it occurred on the amino group to give N6-alkylated purines by C-N bond formation when 2 equiv of CuI were added. A reaction mechanism was also proposed based on our preliminary experimental data.
- Xia, Ran,Niu, Hong-Ying,Qu, Gui-Rong,Guo, Hai-Ming
-
supporting information
p. 5546 - 5549
(2013/01/15)
-
- Intermolecular dehydration of alcohols by the action of copper compounds activated with carbon tetrabromide. synthesis of ethers
-
Copper compounds of the general formula CuXn (X = Cl, Br, I, acac, OAc, C7H4O3, C7H 5O2; n = 1, 2) activated by carbon tetrabromide catalyzed intermolecular dehydration of primary and secondary alcohols with formation of the corresponding ethers.
- Khusnutdinov, R. I.,Bayguzina, A. R.,Gimaletdinova, L. I.,Dzhemilev, U. M.
-
p. 1191 - 1196,6
(2020/10/15)
-
- Brominated methanes as photoresponsive molecular storage of elemental Br2
-
The photochemical generation of elemental Br2 from brominated methanes is reported. Br2 was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low-pressure mercury lamp, wherein the amount and situations of Br2 generation were photochemically controllable. Liquid CH 2Br2 can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br2, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br2 from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br2 that was generated by the photodecomposition of CH2Br2 retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br2 dissolved in CH 2Br2 that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH2Br2, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br2 from CH2Br2 was available for the area-selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br2 that was generated photochemically from CH 2Br2 was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules. The generation of Br 2 from brominated methanes occurred upon photoirradiation under O2. The solutions that contained elemental Br2 were useful for the synthesis of organobromine compounds and the macroscopic photochemical bleaching of colored plants. Copyright
- Kawakami, Kazumitsu,Tsuda, Akihiko
-
p. 2240 - 2252
(2012/11/06)
-
- Evidence for an alternative to the oxygen rebound mechanism in C-H bond activation by non-heme FeIVO complexes
-
The hydroxylation of alkanes by heme FeIVO species occurs via the hydrogen abstraction/oxygen rebound mechanism. It has been assumed that non-heme FeIVO species follow the heme FeIVO paradigm in C-H bond activation reactions. Herein we report theoretical and experimental evidence that C-H bond activation of alkanes by synthetic non-heme Fe IVO complexes follows an alternative mechanism. Theoretical calculations predicted that dissociation of the substrate radical formed via hydrogen abstraction from the alkane is more favorable than the oxygen rebound and desaturation processes. This theoretical prediction was verified by experimental results obtained by analyzing iron and organic products formed in the C-H bond activation of substrates by non-heme FeIVO complexes. The difference in the behaviors of heme and non-heme FeIVO species is ascribed to differences in structural preference and exchange-enhanced reactivity. Thus, the general consensus that C-H bond activation by high-valent metal-oxo species, including non-heme FeIVO, occurs via the conventional hydrogen abstraction/oxygen rebound mechanism should be viewed with caution.
- Cho, Kyung-Bin,Wu, Xiujuan,Lee, Yong-Min,Kwon, Yoon Hye,Shaik, Sason,Nam, Wonwoo
-
supporting information
p. 20222 - 20225
(2013/02/23)
-
- In situ phosphine oxide reduction: A catalytic appel reaction
-
Several important reactions in organic chemistry thrive on stoichiometric formation of phosphine oxides from phosphines. To avoid the resulting burden of waste and purification, cyclic phosphine oxides were evaluated for new catalytic reactions based on in situ regeneration. First, the ease of silane-mediated reduction of a range of cyclic phosphine oxides was explored. In addition, the compatibility of silanes with electrophilic halogen donors was determined for application in a catalytic Appel reaction based on in situ reduction of dibenzophosphole oxide. Under optimized conditions, alcohols were effectively converted to bromides or chlorides, thereby showing the relevance of new catalyst development and paving the way for broader application of organophosphorus catalysis by in situ reduction protocols. Copyright
- Van Kalkeren, Henri A.,Leenders, Stefan H. A. M.,Hommersom, C. Rianne A.,Rutjes, Floris P. J. T.,Van Delft, Floris L.
-
supporting information; experimental part
p. 11290 - 11295
(2011/10/19)
-
