- A novel route for the synthesis of alkanes from glycerol in a two step process using a Pd/SBA-15 catalyst
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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
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- Dehydrohalogenation of haloalkanes promoted by metal halides. Hydrogen halometalates formation and their use as hydrohalogenating agents
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In the dehydrohalogenation of 1,2-dihalo-1,1-diphenylethanes, 1, to 2- halo-1,1-diphenylethene, 2, either at 76°C or at 50°C, promoted by catalytic amount of the anhydrous bromides of Fe(III), Ru(III) and Al(III) and Fe(III) chloride the chemical transformation of the metal halides was observed. In reactions carried out in vacuum or under nitrogen atmosphere, the hydrogen halide eliminated from the organic substrate reacted with the metal halides rendering the unstable hydrogen perhalometalates H+(a)[MX(2+a)]a-. We demonstrate that these compounds behave as hydrogen halide donors in hydrohalogenation of olefins at 4°C.
- Suarez, Angela R.,Martin,, Sandra E.,Martinelli, Marisa,Domine, Marcelo E.,Mazzieri, Maria R.
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- Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity
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Dodecavanadate, [V12O32]4? (V12), possesses a 4.4 ? cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br2 was inserted into V12, inducing the inversion of one of the VO5 square pyramids to form [V12O32(Br2)]4? (V12(Br2)). The inserted Br2 molecule was polarized and showed a peak at 185 cm?1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br2 molecule. Compound V12(Br2) also reacted with propane, n-butane, and n-pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3-bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2-,3-dibromobutane and 2,3-dibromopenane. The unique inorganic cavity traps Br2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br2 shows selective functionalization of alkanes.
- Hayashi, Yoshihito,Inada, Yasuhiro,Katayama, Misaki,Kikukawa, Yuji,Kitajima, Hiromasa,Seto, Kensuke,Watanabe, Daiki,Yamashita, Shohei
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supporting information
p. 14399 - 14403
(2020/07/13)
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- High-purity 5-ethyl-5-(1-methylbutyl)barbituric acid preparation method
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The present invention relates to a preparation method of a drug pentobarbital (1) for sedation, hypnosis, pre-anesthesia administration and anti-convulsion, and provides a new preparation process for preparing high-purity pentobarbital (I) from diethyl ethylmalonate, wherein the process comprises three steps: A, bromination; B, alkylation; and C, cyclization, acidification, and purification. According to the present invention, the method has advantages of simple operation, short production cycle, low energy consumption, mother liquor circulation, less three-waste, stable process, good product quality, high product purity, isomer impurity content of less than 0.1%, high yield and low production cost, and is suitable for industrial production.
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Paragraph 0021; 0022; 0025; 0026; 0029; 0030; 0033; 0034
(2019/10/04)
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- An efficient conversion of alcohols to alkyl bromides using pyridinium based ionic liquids: A green alternative to appel reaction
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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
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p. 651 - 654
(2018/02/09)
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- Identification and Synthesis of Branched Wax-type Esters, Novel Surface Lipids from the Spider Argyrodes?elevatus (Araneae: Theridiidae)
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The analysis of cuticular extracts from the kleptoparasitic spider Argyrodes?elevatus revealed the presence of unusual esters, new for arthropods. These novel compounds proved to be methyl-branched long-chain fatty acid esters with methyl branches located either close or remote from the internally located ester group. The GC/MS analysis of the prosoma lipid blend from the male cuticle contained one major component, undecyl 2-methyltridecanoate (1). In contrast, four major wax-type esters, 2-methylundecyl 2,8-dimethylundecanoate (2), 2,8-dimethylundecyl 2,8-dimethylundecanoate (3), heptadecyl 4-methylheptanoate (4), and 14-methylheptadecyl 4-methylheptanoate (5), were identified in the lipid blend of female prosomata. Structure assignments were based on mass spectra, gas chromatographic retention indices, and microderivatization. Unambiguous proof of postulated structures was ensured by an independent synthesis of all five esters. Preferentially, odd-numbered carbon chains pointed to a distinct biosynthetic pathway, different from that of common fatty acids, because one or two C3 starter units are incorporated during the biosynthesis of all acid and alcohol building blocks present in the five esters. The striking sexual dimorphism together with the unique biosynthesis points to a function of the esters in chemical communication of the spiders, although no behavioral data are currently available to test this assumption.
- Chinta, Satya Prabhakar,Goller, Stephan,Uhl, Gabriele,Schulz, Stefan
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p. 1202 - 1220
(2016/10/03)
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- Terminal-Selective Functionalization of Alkyl Chains by Regioconvergent Cross-Coupling
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Hydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C?H bond functionalization methods. We describe herein a new step-economical approach that enables C?C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross-coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross-coupling then provided access to the corresponding linear arylation product in only two steps.
- Dupuy, Stéphanie,Zhang, Ke-Feng,Goutierre, Anne-Sophie,Baudoin, Olivier
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supporting information
p. 14793 - 14797
(2016/11/23)
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- Highly efficient oxidative bromination of alkanes with the HBr-H 2O2 system in the presence of catalyst
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Various cycloalkanes and straight-chain alkanes were efficiently brominated with an aqueous HBr-H2O2 system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo-cycloalkanes in moderate yields and the straight-chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for Ci￡H activation through bromination. A simple, effective, environmentally friendly method was researched for bromination of alkanes in good yield with HBr as the origin of bromine.
- Li, Yujin,Ju, Jie,Jia, Jianhong,Sheng, Weijian,Han, Liang,Gao, Jianrong
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experimental part
p. 2428 - 2432
(2011/10/03)
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- Direct bromination and iodination of non-activated alkanes by hypohalite reagents
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The direct functionalisation of alkanes through bromination and iodination has been successfully achieved. The combination of stoichiometric mixtures of elemental halogen and sodium alkoxides leads to the formation of alkyl hypobromites and hypoiodites as reagents. The halogenation occurs without external photostimulation under thermal reaction conditions. Georg Thieme Verlag Stuttgart.
- Montoro, Raul,Wirth, Thomas
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p. 1473 - 1478
(2007/10/03)
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- Chemoselective monobromination of alkanes promoted by unactivated MnO 2
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Reaction of alkanes with bromine promoted by unactivated MnO2 gave the corresponding alkylbromides in excellent yield with good chemoselectivity. The MnO2 could be easily recovered and reused.
- Jiang, Xuefeng,Shen, Meihua,Tang, Yu,Li, Chaozhong
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p. 487 - 489
(2007/10/03)
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- Cockroach attractant
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Compounds useful as cockroach attractants, the synthesis of the compounds, and methods of controlling cockroach populations with the compounds are disclosed. The compounds are pyrans having the formula: STR1 wherein: R1 is a methyl, ethyl, propyl, or methoxy group and R2 is a branched alkyl side chain having from 7 to 11 carbons. Preferably, R2 is a 2,4-dimethyl-substituted alkyl group. Most preferably R1 is methyl and R2 is 2,4-dimethylheptanyl. The pyrans can be used as an attractant in cockroach traps comprising, in addition to a pyran according to Formula (I) above, a support and a cockroach restraint. Alternatively, the pyran of the present invention can be combined with a biocontrol agent or an insecticide to form a cockroach control composition.
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- A new simple and industrial process for bromination of alcohols
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Alcohols treated with thionylchloride, followed by chlorine/bromine exchange using gaseous hydrobromic acid and thermal decomposition in the presence of a tertiary amine give the corresponding brominated compounds. The process is regio/stereo selective.
- Mas,Metivier
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p. 2187 - 2191
(2007/10/02)
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- Reactivity of Alkaneselenyl Bromide: Conversion of Alcohols into the Corresponding Alkyl Bromides with Dialkylselenium Dibromide
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The reaction of alcohols with dialkylselenium dibromide gave the corresponding bromides in moderate to high yields.Alkaneselenyl bromide, produced by the thermal decomposition from dialkylselenium dibromide, acts as a brominating agent.The reaction of alcohol with dialkylselenium dichloride afforded the corresponding chlorides, although the yields were realtively low compared with those of the bromide.
- Akabori, Sadatoshi,Takanohashi, Yoshinori
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p. 3482 - 3484
(2007/10/02)
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- SELECTIVE HYDROBROMINATION OF BRANCHED ALCOHOLS USING PHASE TRANSFER CATALYSIS
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In the presence of quaternary ammonium phase transfer catalysts hydrobromination of branched alcohols proceed via selective SN2 mechanism practically without rearrangements.
- Dakka, Gihad,Sasson, Yoel
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p. 1223 - 1224
(2007/10/02)
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- Silylaminyl Radicals. Part 2. Free Radical Chain Halogenation of Hydrocarbons using N-Halogenobis(trialkylsilyl)amines
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The liquid-phase halogenation of a number of hydrocarbons and of 1-chlorobutane by N-halogenobis(trialkylsilyl)amines has been studied using product analysis techniques.The reactions take place by free radical chain mechanisms which involve the propagation steps generalised in equations (A) and (B) (X=Br or Cl).At 353 K, the molar reactivities of toluene (benzylic C-H) and cyclohexane towards (R3Si)2N+RH(R3Si)2NH+R (A) R+(R3Si)2NXRX+(R3Si)2N (B) (Me3Si)2N are approximately equal and toluene is 5.2 times more reactive than perdeuteriotoluene.The relative rates of hydrogen abstraction by (Me3Si)2N and (ButMe2Si)2N from the primary, secondary, and tertiary C-H groups in 2-methylbutane show that the silylaminyl radicals are not only highly reactive but also sterically demanding.Thus, at 333 K the average primary C-H reactivity is 0.6 times that of the tertiary C-H towards attack by (Me3Si)2N, but 4.2 times that of the tertiary C-H towards attack by the more bulky (ButMe2Si)2N.Silylaminyl radicals are much more reactive in hydrogen abstraction than are analogous dialkylaminyl radicals and this difference is interpreted in terms of thermodynamic and polar effects which arise because of the ?-donor-?-acceptor nature of the trialkylsilyl substituent.
- Cook, Malcolm D.,Roberts, Brian P.,Singh, Karamjit
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p. 635 - 644
(2007/10/02)
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