108 results on '"Boron tribromide"'
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2. The synthesis of 3-aryl-3-trifluoromethyl-2,3-dihydro-1H-pyrrolizin-1-ones
- Author
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S. V. Melnykov, V. M. Tkachuk, A. M. Grozav, I. Gillaizeau, and V. A. Sukach
- Subjects
boron tribromide ,cyclocondensation ,3-amino-3-aryltrifluorobutanoic acid esters ,dimethoxytetrahydrofuran ,1h-pyrrolizin-1-ones ,Chemistry ,QD1-999 - Abstract
Aim. To develop the efficient method for the synthesis of 3-aryl-3-trifluoromethyl-2,3-dihydro-1H-pyrrolizin-1-ones as promising scaffolds in design of bioactive compounds. Results and discussion. It has been shown that condensation of 3-amino-3-aryl-4,4,4-trifluorobutanoic acid methyl esters with 2,5-dimethoxytetrahydrofuran is a convenient synthetic approach to 4,4,4-trifluoro-3-aryl-3-(1H-pyrrol-1-yl)methylbutanoic acid methyl esters converted to 3-aryl-3-trifluoromethyl-2,3-dihydro-1H-pyrrolizin-1-ones by the intramolecular Friedel-Crafts reaction. Experimental part. By the interaction of 3-amino-3-aryl-4,4,4-trifluorobutanoic acid methyl esters with 2,5-dimethoxytetrahydrofuranin acetic acid at 70 оC 4,4,4-trifluoro-3-aryl-3-(1H-pyrrol-1-yl)methylbutanoic acid methyl esters were obtained and subsequently cyclized into 3-aryl-3-trifluoromethyl-2,3-dihydro-1H-pyrrolizin-1-ones upon treatment with boron tribromide in dichloromethane at room temperature. The structures of the compounds synthesized were confirmed by LCMS, IR and NMR (1H, 13C, 19F) spectroscopic methods. Conclusions. An efficient two step protocol for the synthesis of 3-aryl-3-trifluoromethyl-2,3-dihydro-1H-pyrrolizin-1-ones has been developed. It includes transformation of 3-amino-3-aryl-4,4,4-trifluorobutanoic acid methyl esters into the corresponding 3-(1H-pyrrol-1-yl) derivatives and their further intramolecular cyclization.
- Published
- 2019
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3. Synthesis of potentially biologically active novel phenolic derivatives of unsymmetrical ureas from substituted phenethylamines.
- Author
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Özgeriş, Bünyamin
- Abstract
Unsymmetrical urea derivatives have been reported to play a significant role in plethora of biological pathways (e.g., neurotransmission, neuromodulation). Notably, urea-based scaffolds are increasingly employed in medicinal chemistry campaigns to engage key protein interactions owing to their tunable physicochemical and structural properties. In this study, we disclose the first examples of unsymmetrical phenethylamine based urea derivatives in aqueous conditions. The reactions involving in-situ generated imidazolide intermediate proceed to completion in the absence of base and under air at room temperature thus allowing access to sensitive functional groups. We also demonstrate a useful product functionalization (i.e., demethylation of 4-methoxyphenethylamine via BBr
3 ) to access the corresponding tyramine analogues. All urea and phenolic derivatives were characterized with1 H NMR,13 C NMR, FT-IR, and elemental analysis. [ABSTRACT FROM AUTHOR]- Published
- 2020
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4. A One Step Method to Produce Boron Emitters.
- Author
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A. Silva, José, Amaro e Silva, Rodrigo, Peral, Ana, and del Cañizo, Carlos
- Subjects
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BORON bromides , *BOROSILICATES , *SOLAR cells , *PHOTOVOLTAIC power systems , *SILICON crystallography , *SEMICONDUCTOR doping - Abstract
A one‐step method to obtain boron emitters for n‐type solar cells based on the use of boron tribromide (BBr3) as a dopant source is developed. During this study several experimental parameters are varied. It is observed that besides the diffusion temperature, the nitrogen gas flux and the BBr3 bubbler temperature have a significant impact on the obtained emitter properties. Using the adequate experimental conditions a homogenous boron emitter without boron rich layer (BRL), a sheet resistance of 77 Ω sq−1 and a dark saturation current <100 fA cm−2 is obtained. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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5. Catechol reactivity: Synthesis of dopamine derivatives substituted at the 6-position.
- Author
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Rote, Jennifer C., Malkowski, Sarah N., Cochrane, C. Skyler, Bailey, Gabrielle E., Brown, Noah S., Cafiero, Mauricio, and Peterson, Larryn W.
- Subjects
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CATECHOLAMINES , *DOPAMINE agents , *NEUROTRANSMITTERS , *METAL detectors , *CHEMICAL shift (Nuclear magnetic resonance) - Abstract
Dopamine is a ubiquitous neurotransmitter essential in the proper functioning of the human body. In addition to this critical role, the catecholamine core has shown utility as a scaffold for numerous drugs and in other applications, like metal detection and adhesive materials. Substituents at the 6-position of dopamine’s catechol core can modulate its stereoelectronic properties, the acidity of its phenolic hydroxyl groups, and the overall hydrophobicity of the molecule. Herein, we report the synthesis of a series of four novel dopamine analogues substituted at the 6-position of catechol core. The1H NMR chemical shift of the aromatic protonmetato the substituent correlated strongly with the Hammettσmconstant, confirming the electronic properties of substituents. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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6. Functionalization of N 2 via Formal 1,3‐Haloboration of a Tungsten(0) σ‐Dinitrogen Complex
- Author
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Anselm Herzog, Rüdiger Bertermann, Felipe Fantuzzi, Soren K. Mellerup, Andrea Deißenberger, Holger Braunschweig, Anna Rempel, and Bernd Engels
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Chemistry ,Organic Chemistry ,Substituent ,chemistry.chemical_element ,General Chemistry ,Borylation ,Catalysis ,chemistry.chemical_compound ,Nucleophile ,Polymer chemistry ,Electrophile ,Moiety ,Lewis acids and bases ,Boron tribromide ,Boron - Abstract
Boron tribromide and aryldihaloboranes were found to undergo 1,3-haloboration across one W-N≡N moiety of a group 6 end-on dinitrogen complex (i.e. trans-[W(N2 )2 (dppe)2 ]). The N-borylated products consist of a reduced diazenido unit sandwiched between a WII center and a trivalent boron substituent (W-N=N-BXAr), and have all been fully characterized by NMR and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Both the terminal N atom and boron center in the W-N=N-BXAr unit can be further derivatized using electrophiles and nucleophiles/Lewis bases, respectively. This mild reduction and functionalization of a weakly activated N2 ligand with boron halides is unprecedented, and hints at the possibility of generating value-added nitrogen compounds directly from molecular dinitrogen.
- Published
- 2020
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7. Boron tribromide as a reagent for anti-Markovnikov addition of HBr to cyclopropanes
- Author
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Matthew H. Gieuw, Ying-Yeung Yeung, Kendall N. Houk, Shuming Chen, and Zhihai Ke
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Bromine ,Proton ,Radical ,Markovnikov's rule ,Regioselectivity ,chemistry.chemical_element ,Ionic bonding ,General Chemistry ,Chemistry ,chemistry.chemical_compound ,chemistry ,Computational chemistry ,Reagent ,Chemical Sciences ,Boron tribromide - Abstract
Although radical formation from a trialkylborane is well documented, the analogous reaction mode is unknown for trihaloboranes. We have discovered the generation of bromine radicals from boron tribromide and simple proton sources, such as water or tert-butanol, under open-flask conditions. Cyclopropanes bearing a variety of substituents were hydro- and deuterio-brominated to furnish anti-Markovnikov products in a highly regioselective fashion. NMR mechanistic studies and DFT calculations point to a radical pathway instead of the conventional ionic mechanism expected for BBr3., Anti-Markovnikov hydrobromination of cyclopropanes was achieved using boron tribromide and water as the bromine and proton sources, respectively.
- Published
- 2020
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8. Unexpected boratranes: BBr3 mediated synthesis and mechanistic insights.
- Author
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Vanucci-Bacqué, Corinne, André-Barres, Christiane, Saffon-Merceron, Nathalie, and Bedos-Belval, Florence
- Subjects
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DENSITY functional theory , *ACID derivatives , *BORIC acid , *LOW temperatures - Abstract
Boratranes synthesis are predictably based on the reactions of triethanolamine derivatives with boric acid, or trialkyl borate and require prolonged heating of the reagents under reflux. Herein, the authors report an efficient synthesis of unexpected boratranes featuring on one hand three six-membered chelating ring or two six-membered and one five-membered chelating ring and on the other hand a trans -annular boron atom is bound to one nitrogen, two oxygen and one carbon atom. These novel boratranes have been synthetized by reacting N , N -bis(2-methoxybenzyl) alkynylamines with BBr 3 in dichloromethane at low temperature. The reaction mechanism was investigated by using density functional theory (DFT) calculations. A mechanistic pathway proceeding through a key dioxazaborecinium intermediate was proposed. This alternative protocol represents a convenient access to dissymmetric and functionalizable boratranes under mild conditions in good yields. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2022
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9. Correlation between Boron–Silicon Bonding Coordination, Oxygen Complexes and Electrical Properties for n-Type c-Si Solar Cell Applications
- Author
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Jinjoo Park, Gyeongbae Shim, Cheolmin Park, Junsin Yi, and Nagarajan Balaji
- Subjects
n-type c-Si solar cell ,Control and Optimization ,Materials science ,Silicon ,Passivation ,Analytical chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,lcsh:Technology ,law.invention ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,law ,0103 physical sciences ,Solar cell ,Electrical and Electronic Engineering ,Boron ,Engineering (miscellaneous) ,Sheet resistance ,010302 applied physics ,boron-diffused layer ,boron tribromide (BBr3) ,Renewable Energy, Sustainability and the Environment ,lcsh:T ,bonding coordination complex ,Carrier lifetime ,021001 nanoscience & nanotechnology ,chemistry ,Boron tribromide ,0210 nano-technology ,Energy (miscellaneous) - Abstract
In this paper, the relationship between coordination complexes and electrical properties according to the bonding structure of boron and silicon was analyzed to optimize the p–n junction quality for high-efficiency n-type crystalline solar cells. The p+ emitter layer was formed using boron tribromide (BBr3). The etch-back process was carried out with HF-HNO3-CH3COOH solution to vary the sheet resistance (Rsheet). The correlation between boron–silicon bonding in coordination complexes and electrical properties according to the Rsheet was analyzed. Changes in the boron coordination complex and boron–oxygen (B–O) bonding in the p+ diffused layer were measured through X-ray photoelectron spectroscopy (XPS). The correlation between electrical properties, such as minority carrier lifetime (τeff), implied open-circuit voltage (iVoc) and saturation current density (J0), according to the change in element bonding, was analyzed. For the interstitial defect, the boron ratio was over 1.8 and the iVoc exceeded 660 mV. Additional gains of 670 and 680 mV were obtained for the passivation layer AlOx/SiNx stack and SiO2/SiNx stack, respectively. The blue response of the optimized p+ was analyzed through spectral response measurements. The optimized solar cell parameters were incorporated into the TCAD tool, and the loss analysis was studied by varying the key parameters to improve the conversion efficiency over 23%.
- Published
- 2020
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10. An Expedient Synthesis of Ketocalix[6]arene Hexamethyl Ether
- Author
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Norbert Itzhak and Silvio E. Biali
- Subjects
Chloroform ,010405 organic chemistry ,Organic Chemistry ,Halogenation ,Ether ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Nucleophilic aromatic substitution ,Intramolecular force ,Calixarene ,Boron tribromide ,Derivative (chemistry) - Abstract
p-tert-Butylcalix[6]arene hexamethyl ether was oxidized in one step to the corresponding ketocalix[6]arene via photochemical bromination (100 W spot lamp) with NBS in a chloroform/water mixture. A pentamethyl ketocalix[6]arene derivative was obtained by reaction of the ketocalix[6]arene hexamethyl ether with boron tribromide dimethyl sulfide complex, and characterized by X-ray crystallography. In the presence of base, the compound undergoes an intramolecular nucleophilic aromatic substitution reaction.
- Published
- 2018
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11. Tungsten Borides: On the Reaction of Tungsten with Boron(III) Bromide
- Author
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Ralf Köppe, Michael Binnewies, Marcus Schmidt, Yuri Grin, Anne Henschel, and Ulrich Burkhardt
- Subjects
Quantum chemical ,Thermal resistance ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Tungsten ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Tungsten borides ,Catalysis ,0104 chemical sciences ,Thermodynamic model ,chemistry.chemical_compound ,chemistry ,Bromide ,Boron tribromide ,0210 nano-technology ,Boron - Abstract
The crucible-free reaction between heated tungsten wires and gaseous boron tribromide yields different tungsten borides. The experiments were carried out at various reaction temperatures and times, revealing the formation of W2 B, WB and WB2 phases. The underlying reactions were analyzed by using thermodynamic model calculations. The stability of the gaseous tungsten bromides was evaluated using quantum chemical methods. While the developed synthesis of phase-pure borides is only possible to a limited extent, it offers a potential route for a formation of protective coatings with high chemical and thermal resistance.
- Published
- 2018
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12. Synthesis and Structural Elucidation of a Pyranomorphinan Opioid and in Vitro Studies
- Author
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Kellie Hom, Mohd. Imran Ansari, Jeffrey R. Deschamps, Rae R. Matsumoto, Jason R. Healy, and Andrew Coop
- Subjects
0301 basic medicine ,medicine.drug_class ,Stereochemistry ,Receptors, Opioid, mu ,010402 general chemistry ,01 natural sciences ,Biochemistry ,03 medical and health sciences ,chemistry.chemical_compound ,Drug tolerance ,Receptors, Opioid, delta ,medicine ,Hydroxymethyl ,Physical and Theoretical Chemistry ,Molecular Structure ,Organic Chemistry ,Drug Tolerance ,0104 chemical sciences ,Analgesics, Opioid ,030104 developmental biology ,chemistry ,Opioid ,Oxymorphone ,Yield (chemistry) ,Boron tribromide ,Two-dimensional nuclear magnetic resonance spectroscopy ,Opioid antagonist ,medicine.drug - Abstract
During optimization of the synthesis of the mixed μ opioid agonist/δ opioid antagonist 5-(hydroxymethyl)oxymorphone (UMB425) for scale-up, it was unexpectedly discovered that the 4,5-epoxy bridge underwent rearrangement on treatment with boron tribromide (BBr3) to yield a novel opioid with a little-studied pyranomorphinan skeleton. This finding opens the pyranomorphinans for further investigations of their pharmacological profiles and represents a novel drug class with the dual profile (μ vs δ) predicted to yield lower tolerance and dependence. The structure was assigned with the help of 1D, 2D NMR and the X-ray crystal structure.
- Published
- 2018
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13. Boron Tribromide-Assisted Chiral Phosphoric Acid Catalysts for Enantioselective [2+2] Cycloaddition
- Author
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Kazuaki Ishihara, Manabu Hatano, Yuta Goto, Tatsuhiro Sakamoto, and Takuya Mochizuki
- Subjects
chemistry.chemical_classification ,Sulfide ,010405 organic chemistry ,Organic Chemistry ,Enantioselective synthesis ,Methacrolein ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,Cycloaddition ,0104 chemical sciences ,Catalysis ,Cyclobutane ,chemistry.chemical_compound ,chemistry ,Boron tribromide ,Phosphoric acid - Abstract
BBr3 -assisted chiral phosphoric acid catalysts for enantioselective [2+2] cycloaddition were developed. The reactions of phenyl vinyl sulfide with α-substituted acroleins proceeded, and the corresponding [2+2] cycloadducts were obtained with high enantioselectivity. In particular, the [2+2] cycloadduct obtained from methacrolein is a synthetically useful optically active cyclobutane, which could be transformed to a key intermediate for (+)-frontalin, a pheromone of Asian elephants.
- Published
- 2018
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14. Synthesis, characterization, and antioxidant activities of new trisubstituted triazoles.
- Author
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Sancak, Kemal, Ünver, Yasemin, Ünlüer, Dilek, Düğdü, Esra, Kör, Gülcan, Çeelık, Fatih, and Bırıncı, Emrah
- Subjects
- *
CHEMICAL synthesis , *ANTIOXIDANTS , *TRIAZOLES , *ALKYLIDENES , *NUCLEAR magnetic resonance , *X-ray spectroscopy , *BORON compounds - Abstract
A series of new 4-(3,4dimethoxyphenethyl)-3,5-akyl/aryl-4H-1,2,4-triazoles (3a-g) were obtained by reaction of ethyl N'-(alkylidene/arylidene)hydrazonate (1) and 2-(3,4-dimethoxy phenyl)ethanamine (2). Compounds 4d, e, and g were synthesized from the reaction of corresponding compounds 3d, e, and g with BBr3 , respectively. The 10 new compounds synthesized were characterized by elemental analyses, IR, ¹ H-NMR, and 13C-NMR spectral data. The structure of compound 3g was inferred through IR, ¹H-, 13C-NMR, elemental analyses, and X-ray spectral techniques. In addition, the newly synthesized chemicals were screened for their antioxidant properties. Among the chemicals tested, 4d, e, and g exhibited the highest degree of antioxidant activity. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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15. Benzylic Bromination of Toluene Derivatives with Boron Tribromide.
- Author
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Chen, Hongbiao, Shen, Litao, and Lin, Yuanbin
- Subjects
- *
BROMINATION , *TOLUENE , *BORON , *CARBON tetrachloride , *BENZYL compounds , *BROMIDES , *BORON bromides - Abstract
A facile method for the benzylic bromination of toluene derivatives was developed. Various substituted toluenes were brominated with boron tribromide as bromine source in carbon tetrachloride at room temperature, affording their corresponding benzyl bromides in good yields. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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16. Mild and efficient conversion of trifluoromethylarenes into tribromomethylarenes using boron tribromide.
- Author
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Chen, Hongbiao, Yin, Jianxiang, and Lin, Yuanbin
- Abstract
Tribromomethylarenes were prepared efficiently, at room temperature, from trifluoromethylarenes with boron tribromide as the brominating reagent. The present process is applicable to the preparation of various substituted benzotribromide derivatives from substituted benzotrifluoride compounds. p-Substituted benzotrifluoride compounds were found to be more reactive than o-substituted isomers under the given reaction conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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17. Synthesis and antiviral properties of some polyphenols related to Salvia genus
- Author
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Queffélec, Clémence, Bailly, Fabrice, Mbemba, Gladys, Mouscadet, Jean-François, Hayes, Sean, Debyser, Zeger, Witvrouw, Myriam, and Cotelle, Philippe
- Subjects
- *
ANTIVIRAL agents , *POLYPHENOLS , *PHENOLS , *GALLIC acid - Abstract
Abstract: An efficient synthesis of the acid part of salvianolic acid E 2 is described. Compound 2 was obtained from vanillin in 10 steps and 21% overall yield. During the synthesis of 2 an unexpected 5-oxo-4b,9b-dihydroindano[1,2-b]benzofuran rac-12 was isolated. Both compounds together with the acid part of salvianolic acid D were active as HIV-1 integrase inhibitors at the submicromolar level. But they did not inhibit the replication of the virus on MT-4 cells. [Copyright &y& Elsevier]
- Published
- 2008
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18. Direct Synthesis of Bulk Boron-Doped Graphitic Carbon
- Author
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Emanuel Billeter, Maksym V. Kovalenko, Laura Piveteau, Nicholas P. Stadie, Kostiantyn V. Kravchyk, and Max Döbeli
- Subjects
Materials science ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Boron carbide ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Alkali metal ,01 natural sciences ,0104 chemical sciences ,Anode ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Graphitic carbon ,Graphite ,Boron tribromide ,0210 nano-technology ,Benzene ,Boron - Abstract
The single-step reaction of benzene and boron tribromide in a closed reactor at elevated temperature (800 °C) results in the synthesis of bulk boron-doped graphitic carbon. Materials of continuously tunable composition BCx′ are accessible (x ≥ 3), exhibiting the structure of a solid-solution of boron within turbostratic graphite (G′). Upon extended heat treatment or at higher temperatures, graphitic BCx′ is leached of boron and undergoes a phase separation into boron carbide and graphite. Higher boron content is correlated with an increased maximum capacity for alkali metal ions, making graphitic BCx′ a promising candidate anode material for emerging sodium-ion batteries.
- Published
- 2017
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19. <atl>Intramolecular cyclization of benzyl-substituted cyclopentadienyl titanium dichlorides promoted by boron tribromide
- Author
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Qian, Yanlong, Huang, Jiling, Ding, Kai, Zhang, Yue, Huang, Qinglan, Chen, Xiao Ping, Chan, Albert S.C., and Wong, Wing Tak
- Subjects
- *
HALOGEN compounds , *RING formation (Chemistry) - Abstract
Intramolecular cyclization of α,α-alkyl-ortho-methoxybenzylcyclopentadienyl titanium complexes to form titanoxacycle complexes promoted by BBr3 has been studied. A probable two-step mechanism involving halogen exchange and intramolecular elimination was proposed. Four related benzyl-substituted cyclopentadienyl titanium complexes have been studied by X-ray crystallography. [Copyright &y& Elsevier]
- Published
- 2002
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20. Reaction of Triethyl Phosphite with Boron Tribromide.
- Author
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Lewkowski, Jarosłlaw, Mortier, Jacques, and Vaultier, Michel
- Abstract
Reaction of boron tribromide with triethyl phosphite led to the formation of triethyl tribromoborophosphate 1, a complex bearing a P→B bond. [ABSTRACT FROM AUTHOR]
- Published
- 2000
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21. Synthesis of Nepetoidin B
- Author
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John H. Grabber, Yukiko Tsuji, John Ralph, Matthew R. Regner, and Vitaliy I. Timokhin
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Nepetoidin B ,natural products ,010405 organic chemistry ,Organic Chemistry ,letter ,demethylation ,01 natural sciences ,0104 chemical sciences ,Baeyer–Villiger oxidation ,010404 medicinal & biomolecular chemistry ,chemistry.chemical_compound ,chemistry ,medicinal chemistry ,Yield (chemistry) ,Organic chemistry ,Boron tribromide ,Demethylation - Abstract
The first synthesis of nepetoidin B in an overall yield of 17% was achieved in two steps through Baeyer–Villiger oxidation of commercially available 1,5-bis(3,4-dimethoxyphenyl)-1,4-pentadien-3-one with oxone to produce the tetramethylated nepetoidin B, followed by demethylation using boron tribromide.
- Published
- 2018
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22. Total Synthesis of Viniferifuran, Resveratrol-Piceatannol Hybrid, Anigopreissin A and Analogues - Investigation of Demethylation Strategies
- Author
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Mikael Elofsson and Duc Duy Vo
- Subjects
natural products ,Iodide ,resveratrol oligomers ,Resveratrol ,010402 general chemistry ,01 natural sciences ,stilbenoids ,chemistry.chemical_compound ,Organic chemistry ,total synthesis ,polyphenols ,Demethylation ,Piceatannol ,chemistry.chemical_classification ,Organisk kemi ,Full Paper ,biology ,010405 organic chemistry ,Organic Chemistry ,demethylation ,Total synthesis ,General Chemistry ,Full Papers ,biology.organism_classification ,Boron trichloride ,0104 chemical sciences ,chemistry ,Tetra ,Boron tribromide - Abstract
Resveratrol‐based natural products constitute a valuable source of unique compounds with diverse biological activities. In this report we investigate demethylation strategies to minimize formation of cyclized and dimerized products during the synthesis of viniferifuran and analogues. We found that boron trichloride/tetra‐n‐butylammonium iodide (BCl3/TBAI) is typically more effective than boron tribromide (BBr3). Based on these findings we carried out the first syntheses of dehydro‐δ‐viniferin, resveratrol‐piceatannol hybrid and anigopreissin A. In addition, we have developed a short and efficient route to viniferifuran that was obtained in 13% yield over six steps.
- Published
- 2016
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23. Boron Tribromide-Assisted Chiral Phosphoric Acid Catalyst for a Highly Enantioselective Diels–Alder Reaction of 1,2-Dihydropyridines
- Author
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Matsujiro Akakura, Yuta Goto, Atsuto Izumiseki, Kazuaki Ishihara, and Manabu Hatano
- Subjects
Indole test ,Enantioselective synthesis ,Nanotechnology ,General Chemistry ,Catharanthine ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Organic chemistry ,Boron tribromide ,Brønsted–Lowry acid–base theory ,Phosphoric acid ,Diels–Alder reaction - Abstract
BBr3-chiral phosphoric acid complexes are highly effective and practical Lewis acid-assisted Brønsted acid (LBA) catalysts for promoting the enantioselective Diels-Alder (DA) reaction of α-substituted acroleins and α-CF3 acrylate. In particular, the DA reaction of α-substituted acroleins with 1,2-dihydropyridines gave the corresponding optically active isoquinuclidines with high enantioselectivities. Moreover, transformations to the key intermediates of indole alkaloids, catharanthine and allocatharanthine, are demonstrated.
- Published
- 2015
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24. Fast colorimetric titration protocol for quantification of boron tribromide
- Author
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Andrew L. Korich, Talon M. Kosak, Jason G. Gillmore, Amber J. Prins, and Brianna N. Barbu
- Subjects
010405 organic chemistry ,Chemistry ,Organic Chemistry ,Inorganic chemistry ,Analytical chemistry ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Catalysis ,Adduct ,chemistry.chemical_compound ,Drug Discovery ,Titration ,Lewis acids and bases ,Boron tribromide ,Boron ,Stoichiometry - Abstract
N,N-Dimethylaniline (DMA) was identified as a colorimetric titrant for accurate quantification of boron tribromide (BBr3) solutions. The initial 1:1 DMA/BBr3 Lewis acid–base adduct formed upon addition of the first equivalent of BBr3 is bright blue in color. Addition of catalytic quantities of BBr3 beyond the first equivalent initiates an instantaneous change in the solution from blue to yellow. This methodology will allow for accurate quantification of BBr3 so that proper stoichiometric amounts of BBr3 may be used to facilitate a broad range of organic transformations. Download : Download high-res image (61KB) Download : Download full-size image
- Published
- 2016
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25. Boron tribromide mediated debenzylation of benzylamino and benzyloxy groups
- Author
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Paliakov, Ekaterina and Strekowski, Lucjan
- Subjects
- *
QUINOLINE , *ORGANOBORON compounds , *SUBSTITUTION reactions , *AMINO compounds - Abstract
The treatment of 2(or 4)-benzylamino substituted quinolines, 9-benzylaminoacridine, 2-benzylaminopyridine, a 4-benzyloxyquinoline, and an N-benzyloxyamidine with BBr3 yields the corresponding amino or hydroxy substituted compounds. The scope and limitations of this novel reaction are discussed. [Copyright &y& Elsevier]
- Published
- 2004
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26. Synthesis of substituted 2-heteroarylbenzazol-5-ol derivatives as potential ligands for estrogen receptors
- Author
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Abbas Shafiee, Latifeh Navidpour, and Sina Rezazadeh
- Subjects
Organic Chemistry ,Hydrazine ,Alkylation ,Pyrazole ,Biochemistry ,Medicinal chemistry ,Quinone ,chemistry.chemical_compound ,Perchlorate ,chemistry ,Benzyl alcohol ,Drug Discovery ,Pyridine ,Organic chemistry ,Boron tribromide - Abstract
Exposure to estrogen is associated with increased risk of breast and other types of human cancer. One therapeutic goal would be the creation of new molecules that would retain hormonal potency while incorporating features to retard or prevent quinone toxicity. Hence, new structures closely related to ERB-041, a known ERβ selective agonist, were synthesized whereas the phenol ring is substituted with non-quinone forming rings such as pyrazole, 2-pyrimidine-2(1H)-one or pyridine-2(1H)-one. 2-Methyl-5-methoxy-1,3-benzoxazoles (or 1,3-benzothiazole) are key intermediates for the production of the pyrazole and pyrimidine-2(1H)-one analogs. The required 1,3-benzoxazoles were synthesized starting from reduction of 2-nitro-4-methoxyphenols, followed by condensation with trimethyl orthoacetate. Then, the diiminium perchlorate intermediates were prepared from the latter compounds by Vilsmeier–Haack reaction. The reaction of the resulting intermediates with hydrazine hydrate and guanidium chloride afforded the title pyrazole and pyrimidine-2(1H)-ones, respectively. The pyridine analogs were synthesized starting from the reaction of 2-amino-4-methoxyphenols with 6-bromopyridine-3-carboxaldehyde followed by oxidation with DDQ to afford bromopyridines. These compounds were next treated with benzyl alcohol in the presence of potassium tert-butoxide to afford 2-benzyloxypyridine, which in subsequent dealkylation with boron tribromide produced the title pyridine-2-(1H)-ones.
- Published
- 2013
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27. Palladium-Mediated Strategies for Functionalizing the Dihydroazulene Photoswitch: Paving the Way for Its Exploitation in Molecular Electronics
- Author
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Martyn Jevric, Mogens Brøndsted Nielsen, and Søren Lindbæk Broman
- Subjects
Molecular switch ,chemistry.chemical_compound ,Photoswitch ,chemistry ,Suzuki reaction ,Organic Chemistry ,Molecular electronics ,Organic chemistry ,Regioselectivity ,chemistry.chemical_element ,Boron tribromide ,Palladium ,Stille reaction - Abstract
The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch has attracted interest as a molecular switch for advanced materials and molecular electronics. We report here two synthetic approaches using palladium catalysis for synthesizing dihydroazulene (DHA) photoswitches with thioacetate anchoring groups intended for molecular electronics applications. The first methodology involves a Suzuki coupling using tert-butyl thioether protecting groups. Conversion to the thioacetate using boron tribromide/acetyl chloride results in the formation of the product as a mixture of regioisomers mediated by a ring-opening reaction. The second approach circumvents isomerization by the synthesis of stannanes as intermediates and their use in a Stille coupling. Although fully unsaturated azulenes are formed as byproducts during the synthesis of the DHA stannanes, this approach allowed the regioselective incorporation of the thioacetate anchoring group in either one of the two ends (positions 2 or 7) or at both.
- Published
- 2013
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28. Functionalizations of Aryl CH Bonds in 2-Arylpyridines via Sequential Borylation and Copper Catalysis
- Author
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Liting Niu, Daoshan Yang, Hua Fu, and Haijun Yang
- Subjects
chemistry.chemical_compound ,Ammonium bromide ,chemistry ,Aryl ,Reagent ,Functional group ,Organic chemistry ,Halide ,General Chemistry ,Boron tribromide ,Borylation ,Catalysis - Abstract
Selective functionalizations of aryl CH bonds in 2-arylpyridines have been developed via sequential borylation and aerobic oxidative copper catalysis, and the corresponding aryl halides, sulfones, azides and arylamines were obtained in good yields. The protocol uses cheap and readily available boron tribromide (BBr3) as the borylating reagent, and inorganic salts (potassium iodide, ammonium bromide, sodium alkylsulfinates, sodium azide) as the functional group sources. This method makes functionalizations of aryl CH bonds easy.
- Published
- 2012
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- View/download PDF
29. Synthesis and reactivity of dimethoxy-functionalised Tröger’s base analogues
- Author
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Qasim M. Malik, Sadia Ijaz, Donald C. Craig, and Andrew C. Try
- Subjects
chemistry.chemical_compound ,chemistry ,Organic Chemistry ,Drug Discovery ,Organic chemistry ,Reactivity (chemistry) ,Boron tribromide ,Chirality (chemistry) ,Biochemistry ,Chemical synthesis ,Tröger's base ,Demethylation - Abstract
Troger’s base analogues were prepared bearing methoxy groups in the 1,7-, 2,8-, 3,9- or 4,10-positions. These compounds were converted to their dihydroxy analogues in excellent yields upon treatment with boron tribromide and the 4,10-dihydroxy analogue could be prepared by directly from 4-hydroxyaniline. The synthetic utility of the dihydroxy-functionalised compounds as building blocks was demonstrated by the synthesis of a dialkoxy and a diester Troger’s base analogue.
- Published
- 2011
- Full Text
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30. An efficient approach to sulfate metabolites of polychlorinated biphenyls
- Author
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Xueshu Li, Larry W. Robertson, Sean Parkin, Michael W. Duffel, and Hans-Joachim Lehmler
- Subjects
lcsh:GE1-350 ,Persistent organic pollutant ,Chemical Phenomena ,Sulfates ,food and beverages ,Polychlorinated Biphenyls ,Article ,Chemistry ,chemistry.chemical_compound ,Sulfation ,chemistry ,Ammonium formate ,Organic chemistry ,Phenol ,Environmental Pollutants ,Boron tribromide ,Sulfate ,Benzene ,lcsh:Environmental sciences ,Mutagens ,General Environmental Science ,Demethylation - Abstract
Polychlorinated biphenyls (PCBs), a major class of persistent organic pollutants, are metabolized to hydroxylated PCBs. Several hydroxylated PCBs are substrates of cytosolic phase II enzymes, such as phenol and hydroxysteroid (alcohol) sulfotransferases; however, the corresponding sulfation products have not been isolated and characterized. Here we describe a straightforward synthesis of a series of ten PCB sulfate monoesters from the corresponding hydroxylated PCBs. The hydroxylated PCBs were synthesized by coupling chlorinated benzene boronic acids with appropriate brominated (chloro-)anisoles, followed by demethylation with boron tribromide. The hydroxylated PCBs were sulfated with 2,2,2-trichloroethyl chlorosulfate using DMAP as base. Deprotection with zinc powder/ammonium formate yielded the ammonium salts of the desired PCB sulfate monoesters in good yields when the sulfated phenyl ring contained no or one chlorine substituent. However, no PCB sulfate monoesters were isolated when two chlorines were present ortho to the sulfated hydroxyl group. To aid with future quantitative structure activity relationship studies, the structures of two 2,2,2-trichloroethyl-protected PCB sulfates were verified by X-ray diffraction. Keywords: Biaryls, Polychlorinated biphenyls (PCBs), Sulfates, 2,2,2-Trichloroethyl (TCE) group, Metabolites
- Published
- 2010
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31. Access to Resorcylic Acid Lactones via Phosphonate Based Intramolecular Olefination
- Author
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Paul V. Murphy, Carmela Napolitano, and Patrick McArdle
- Subjects
Models, Molecular ,inorganic chemicals ,chemistry.chemical_classification ,Addition reaction ,Intramolecular reaction ,Organic Chemistry ,Molecular Conformation ,Organophosphonates ,Stereoisomerism ,Alkenes ,Boron trichloride ,Phosphonate ,Lactones ,chemistry.chemical_compound ,chemistry ,Intramolecular force ,Organic chemistry ,Boron tribromide ,Enone ,Lactone - Abstract
An approach to resorcylic acid lactones is described, exploiting an intramolecular olefination reaction for the generation of the 14-membered macrolactone. The synthetic route gave zearalenone precursors, and the preparations of other RAL analogues, trans- and cis-resorcylides are included, the latter being prepared by photoisomerization of the trans-isomer. β-Haloketone derivatives were also prepared in a highly stereoselective manner by conjugate addition of chloride or bromide to the E-enone using boron trichloride and boron tribromide, respectively.
- Published
- 2010
- Full Text
- View/download PDF
32. Modified approach for preparing (E)-stilbenes related to resveratrol, and evaluation of their potential immunobiological effects
- Author
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Miloš Buděšínský, Jan Šmidrkal, Juraj Harmatha, Zdeněk Zídek, Vladimír Filip, Karel Vokáč, Roman Merkl, and Eva Kmoníčková
- Subjects
chemistry.chemical_compound ,Pterostilbene ,Polyphenol ,Chemistry ,Organic chemistry ,Molecule ,Biological activity ,General Chemistry ,Boron tribromide ,Resveratrol ,Boron trichloride ,Isopropyl - Abstract
Resveratrol and closely related stilbenoids belong to the most intensively studied biologically active compounds. This interest evoked several attempts to prepare such compounds in a convenient synthetic way. Our approach allowed obtaining largely methoxystilbenes, formed asE-isomers only (using Wittig–Horner synthesis as the key step), which were further demethylated by boron tribromide. The hydroxymethoxystilbenes (e.g. pterostilbene) were prepared using isopropyl protection, later selectively deprotected by boron trichloride. The method is suitable for preparing such compounds in a large amount. Effects of the obtained stilbene derivatives on immunobiological responses triggered by lipopolysacharide and interferon-γ were tested under in vitro conditions. Namely production of nitric oxide (NO) was investigated, and relation between the molecular structure and immunobiological activity was assessed.
- Published
- 2010
- Full Text
- View/download PDF
33. Synthesis of a Range of Polyhydroxy 8-Aryl Flavones
- Author
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Dong Hee Yoon, Lesley Larsen, and Rex T. Weavers
- Subjects
chemistry.chemical_classification ,chemistry.chemical_compound ,chemistry ,Suzuki reaction ,Dimethyl sulfoxide ,Aryl ,Organic Chemistry ,Organic chemistry ,chemistry.chemical_element ,Boron tribromide ,Iodine ,Flavones - Abstract
The 8-iodo flavones formed by cyclization of benzyl-protected chalcones with iodine in dimethyl sulfoxide have been transformed by a Suzuki coupling reaction into a variety of 8-aryl derivatives. Deprotection with boron tribromide has generated a family of new 8-aryl flavones containing four to eight hydroxyl groups.
- Published
- 2009
- Full Text
- View/download PDF
34. 4-Arylation of 3-alkoxypyrazoles
- Author
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Yves L. Janin, Sandrine Guillou, Mikhail S. Ermolenko, Olivier Nesmes, Institut de Chimie des Substances Naturelles (ICSN), Centre National de la Recherche Scientifique (CNRS), Chimie Organique, Institut Pasteur [Paris]-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut Pasteur [Paris] (IP)-Centre National de la Recherche Scientifique (CNRS), and Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[CHIM.ORGA]Chemical Sciences/Organic chemistry ,010405 organic chemistry ,Aryl ,Organic Chemistry ,Alkylation ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Chemical synthesis ,Combinatorial chemistry ,Coupling reaction ,0104 chemical sciences ,chemistry.chemical_compound ,Suzuki reaction ,chemistry ,Drug Discovery ,Electrophile ,Organic chemistry ,Reactivity (chemistry) ,Boron tribromide ,ComputingMilieux_MISCELLANEOUS - Abstract
Following the study of the alkoxypyrazoles nitrogen's reactivity toward arylation or alkylation reactions, we report here our results on the introduction of various aryl groups on carbon 4 position of 3-alkoxypyrazoles. This was achieved from the corresponding 4-halogeno derivatives via a Suzuki–Miyaura aryl–aryl coupling reaction. The unexpected difficulties (lack of reactivity or unwanted halogen reduction) encountered in the C-4 arylation of NH-free 4-halogenopyrazoles led us to design solutions to this recurrent problem. The cleavage of the 3-alkoxy group was also investigated using hydrogen bromide in acetic acid or boron tribromide in dichloromethane. This led, in one case, to the observation of a remarkable neighboring group-assisted electrophilic aryl boronylation. This second part of our work paves the way to the synthesis of many original chemical libraries featuring 3-alkoxy 1,4-diaryl pyrazoles as well as the corresponding 1,4-diaryl pyrazol-3-ones.
- Published
- 2009
- Full Text
- View/download PDF
35. Regioselective synthesis of ω-bromo-3-ketosulfones, ω-bromo-3-ketonitriles and 2-(ω-bromoalkyl)benzofurans based on a ‘ring-closing/ring-opening’ strategy
- Author
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Peter Langer, Nasir Rasool, Muhammad A. Rashid, Christine Fischer, and Helmut Reinke
- Subjects
chemistry.chemical_compound ,Chemistry ,Organic Chemistry ,Drug Discovery ,Regioselectivity ,Boron tribromide ,Ring (chemistry) ,Biochemistry ,Medicinal chemistry ,Boron trichloride - Abstract
ω-Bromo-3-ketosulfones, ω-bromo-3-ketonitriles and various functionalized 2-(ω-bromoalkyl)benzofurans were chemo- and regioselectively prepared by application of a ‘ring-closing/ring-opening’ strategy. The cyclization of 3-ketosulfone and 3-ketonitrile dianions with 1-bromo-2-chloroethane or 1,4-dibromobut-2-ene afforded functionalized 2-alkylidenetetrahydrofurans which were subsequently cleaved by reaction with boron tribromide or boron trichloride to give the final products.
- Published
- 2007
- Full Text
- View/download PDF
36. First Chemical Synthesis of the Antiviral Agents S2502 and S2507
- Author
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Krisztina Vukics and Karsten Krohn
- Subjects
chemistry.chemical_compound ,chemistry ,Acetylacetone ,Biomimetic synthesis ,Organic Chemistry ,Organic chemistry ,Transesterification ,Boron tribromide ,Chemical synthesis ,Ether cleavage ,Isomerization ,Catalysis ,Saponification - Abstract
The first chemical synthesis of S2502 and S2507, highly active antiviral, bioengineered fermentation products, has been achieved using a biomimetic approach. Key steps of the synthesis involved addition of the dianion of acetylacetone to isochromene 10, followed by boron tribromide mediated simultaneous methyl ether cleavage, E/ Z isomerization, cyclization, and transesterification/saponification to give S2502 ( 7) and S2507 ( 8). In a related reaction, the analogous esters 20 and 21 were obtained by treatment of isochromene 10 with the dianion of methyl acetoacetate, followed by boron tribromide treatment.
- Published
- 2007
- Full Text
- View/download PDF
37. Non-target screening of extractable and non-extractable organic xenobiotics in riverine sediments of Ems and Mulde Rivers, Germany
- Author
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Jan Schwarzbauer and Alexander Kronimus
- Subjects
Geologic Sediments ,Health, Toxicology and Mutagenesis ,Industrial Waste ,Diphenylmethane ,Toxicology ,Gas Chromatography-Mass Spectrometry ,Xenobiotics ,chemistry.chemical_compound ,Rivers ,Water Supply ,Germany ,Phenols ,Organic Chemicals ,Water pollution ,Tetramethylammonium hydroxide ,Sewage ,Water Pollution ,Extraction (chemistry) ,Agriculture ,General Medicine ,Pollution ,Ruthenium tetroxide ,chemistry ,Environmental chemistry ,Boron tribromide ,Gas chromatography–mass spectrometry ,Environmental Monitoring - Abstract
Subaquatic sediment samples derived form Elbe and Mulde Rivers, Germany, were analyzed for extractable and non-extractable anthropogenic organic compounds by a non-target screening approach. Applied methodologies were gas chromatography-mass spectrometry, dispersion extraction and degradation procedures, particularly alkaline and acidic hydrolysis, boron tribromide treatment, ruthenium tetroxide oxidation as well as pyrolysis and TMAH (tetramethylammonium hydroxide)-thermochemolysis. Numerous compounds were identified, including halogenated benzenes, anisoles, styrenes, alkanes, diphenylmethane derivates, anilines, phenols and diphenyl ethers. The results were interpreted with respect to compound specific modes of incorporation as well as to potential sources (e.g. municipal, agricultural, industrial). Extractable and non-extractable fractions differed significantly with respect to their qualitative and quantitative composition. For example, quantities in the extractable and non-extractable fractions of chlorinated benzenes differed up to factor 50. Among other significant results, the investigation revealed hints for a dependence of the mode of incorporation of chlorinated benzenes on their substitution pattern.
- Published
- 2007
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- View/download PDF
38. Ion−Molecule Chemistry within Boron Tribromide Clusters: Experiment and Theory
- Author
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Kathryn E. Kautzman, David A. Hales, Nathan G. Williams, Michael P. Barker, and Pamela A. Haile
- Subjects
law.invention ,Ion ,Adduct ,chemistry.chemical_compound ,Crystallography ,chemistry ,Computational chemistry ,Reflectron ,law ,Physics::Atomic and Molecular Clusters ,Cluster (physics) ,Molecule ,Density functional theory ,Boron tribromide ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Electron ionization - Abstract
Molecular clusters of BBr3 were subjected to electron ionization and mass analysis in a reflectron time-of-flight mass spectrometer. Five series of cluster ions were observed, with formulas corresponding to each of the possible fragment ions of BBr3 being solvated by neutral BBr3 molecules. Geometry optimizations on the observed cluster ions using density functional theory (B3LYP/6-31G*) predict that fragment ions smaller than BBr3+ undergo reactions with neutral BBr3 molecules to form covalently bound adduct species that function as core ions within the clusters. Once all boron atoms are saturated, the reactions cease, and larger cluster ions consist of BBr3 molecules loosely bound to the core ions. Divalent bromine atoms are present in at least three of the cluster ions, and most of the intermolecular contact within the clusters is between Br atoms. Enthalpies of formation, addition reactions, and BBr3 elimination from the cluster ions were derived from B3LYP and MP2 calculations at the B3LYP/6-31G* geometries using both the 6-31G* and the 6-311++G(2df,2p) basis sets. The results are compared to limiting expectations based on known bulk thermochemistry.
- Published
- 2007
- Full Text
- View/download PDF
39. Synthesis of Phosphane Oxide Bridged Bis- and Triscatechol Derivatives
- Author
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Markus Albrecht and Yun Song
- Subjects
inorganic chemicals ,Catechol ,Phosphoryl chloride ,Phosphorus ,Organic Chemistry ,Supramolecular chemistry ,Oxide ,chemistry.chemical_element ,Catalysis ,chemistry.chemical_compound ,chemistry ,Suzuki reaction ,Polymer chemistry ,Organic chemistry ,Boron tribromide ,Phosphorus trichloride - Abstract
Linear biscatechols and triangular triscatechols possessing spacers containing phosphane oxide were synthesized. For this, the central phosphorus was introduced by the reaction of active organometallic intermediates with either dichlorophenylphosphane or phosphorus trichloride/phosphoryl chloride. In the final steps, the methyl ethers at the veratrol units were cleaved by boron tribromide to afford the free phosphane oxide catechol derivatives, which in metal-directed self-assembly processes would lead to helical or tetrahedral supramolecular aggregates.
- Published
- 2006
- Full Text
- View/download PDF
40. Synthesis and X‐Ray Analysis of a New [6]Helicene
- Author
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Béchir Ben Hassine, Taha Guerfel, Riadh El Abed, and Faouzi Aloui
- Subjects
chemistry.chemical_compound ,Crystallography ,Denticity ,Transition metal atoms ,chemistry ,Helicene ,Yield (chemistry) ,Heck reaction ,Organic Chemistry ,Organic chemistry ,Boron tribromide ,X ray analysis ,Hexahelicene - Abstract
A new disubstituted hexahelicene derivative 3 bearing methoxy functions at positions 3 and 14 has been prepared in racemic form through a Heck reaction followed by photocyclodehydrogenation. Suitable crystals of rac‐3 were analyzed by X‐ray crystallography and showed similar geometry to the structure of hexahelicene itself. Deprotection of 3 using boron tribromide led to 3,14‐dihydroxyhexahelicene 4 in quantitative yield. The complexation of transition metal atoms seemed to be quite possible by these two bidentate hexahelicene derivatives.
- Published
- 2006
- Full Text
- View/download PDF
41. Convenient Synthesis of ε-Halo-β-ketoesters and γ,γ‘-Dibromoalkanones by Regio- and Chemoselective Reaction of 2-Alkylidenetetrahydrofurans with Boron Trihalides: A 'Ring-Closure/Ring-Cleavage' Strategy
- Author
-
Esen Bellur and Peter Langer
- Subjects
chemistry.chemical_compound ,Chemistry ,Organic Chemistry ,Regioselectivity ,Halide ,chemistry.chemical_element ,Boron tribromide ,Chemoselectivity ,Ring (chemistry) ,Boron ,Chemical synthesis ,Combinatorial chemistry ,Boron trichloride - Abstract
The reaction of boron tribromide and boron trichloride with 2-alkylidenetetrahydrofurans, readily available on the basis of cyclizations of free and masked dianions with 1,2-dielectrophiles, allowed an efficient synthesis of a variety of carbonyl compounds with remote halide functionality. This includes the chemo- and regioselective synthesis of 6-bromo- and 6-chloro-3-oxoalkanoates and 1,7-dibromoheptan-4-ones. The approach outlined herein can be regarded as a “ring-closure/ring-cleavage” strategy.
- Published
- 2005
- Full Text
- View/download PDF
42. A Novel Approach in Cinnamic Acid Synthesis: Direct Synthesis of Cinnamic Acids from Aromatic Aldehydes and Aliphatic Carboxylic Acids in the Presence of Boron Tribromide
- Author
-
Fulga Tanasa, Constantin I. Chiriac, and Marioara Onciu
- Subjects
Boron Compounds ,Bromides ,Carboxylic Acids ,Chemistry, Organic ,Pharmaceutical Science ,Models, Biological ,Article ,Analytical Chemistry ,lcsh:QD241-441 ,chemistry.chemical_compound ,boron tribromide/4-DMAP ,lcsh:Organic chemistry ,Cinnamic acid synthesis ,Heterocyclic Compounds ,Cinnamic acids ,direct synthesis ,activating agent ,Drug Discovery ,Pyridine ,Organic chemistry ,Physical and Theoretical Chemistry ,Aldehydes ,Organic Chemistry ,Fatty Acids ,Solvent ,chemistry ,Chemistry (miscellaneous) ,Cinnamates ,Reagent ,Molecular Medicine ,Boron tribromide - Abstract
Cinnamic acids have been prepared in moderate to high yields by a new direct synthesis using aromatic aldehydes and aliphatic carboxylic acids, in the presence of boron tribromide as reagent, 4-dimethylaminopyridine (4-DMAP) and pyridine (Py) as bases and N-methyl-2-pyrolidinone (NMP) as solvent, at reflux (180-190 degrees C) for 8-12 hours.
- Published
- 2005
43. Synthesis of polychlorinated biphenyls and their metabolites with a modified Suzuki-coupling
- Author
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Sean Parkin, Larry W. Robertson, Hans-Joachim Lehmler, and Izabela Kania-Korwel
- Subjects
inorganic chemicals ,Environmental Engineering ,Health, Toxicology and Mutagenesis ,Chemical synthesis ,Catalysis ,chemistry.chemical_compound ,Suzuki reaction ,Benzene Derivatives ,Environmental Chemistry ,Organic chemistry ,Benzene ,Dichloromethane ,Molecular Structure ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Boronic Acids ,Polychlorinated Biphenyls ,Pollution ,Models, Chemical ,chemistry ,Ferrocene ,Bromobenzene ,Environmental Pollutants ,Boron tribromide ,Palladium ,Boronic acid - Abstract
A modified procedure for the synthesis of polychlorinated biphenyls (PCBs) utilizing the Suzuki-coupling, a palladium-catalyzed cross-coupling reaction, is described. The coupling of (chlorinated) benzene boronic acids with bromochlorobenzenes, using Pd(dppf)(2)Cl(2) (dppf = 1,1'-bis(diphenylphosphino)ferrocene) as the catalyst and aqueous sodium carbonate as the base, gave the desired PCB congeners in moderate to good yields. Eleven PCB congeners, including environmentally important PCB congeners and metabolites, were synthesized using this modified procedure. This new catalyst Pd(dppf)(2)Cl(2) offers the advantage of being less air-sensitive and has a longer shelf life compared to Pd(PPh(4))(4). Three new (di-)methoxylated PCB congeners were synthesized using the same procedure by either coupling a chlorinated benzene boronic acid with a bromo (di-)methoxybenzene or by coupling a (di-)methoxy benzene boronic acid with a chlorinated bromobenzene. The dimethoxylated PCB congeners were readily converted into the respective dihydroxylated PCB derivatives using boron tribromide in dichloromethane. This approach offers the advantage of high selectivity and moderate to good yields compared to conventional methods such as the Cadogan reaction and allows the use of less toxic starting materials.
- Published
- 2004
- Full Text
- View/download PDF
44. Application of the Sol-Gel Method at the Fabrication of Microstructure Fibers
- Author
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Milos Hayer, Ivan Kašík, Jan Mrázek, Daniela Berková, and Vlastimil Matejec
- Subjects
Materials science ,Fabrication ,General Chemistry ,Condensed Matter Physics ,Microstructure ,Rod ,Electronic, Optical and Magnetic Materials ,Biomaterials ,chemistry.chemical_compound ,chemistry ,Stack (abstract data type) ,Alkoxide ,Materials Chemistry ,Ceramics and Composites ,Fiber ,Boron tribromide ,Composite material ,Sol-gel - Abstract
This paper presents results on using the sol-gel process for the preparation of microstructure fibers (MSFs). In this preparation the sol-gel method is used for the formation of bonds between silica tubes and silica rods in the input stacks for MSF drawing and for filling-in the interstices between these parts. Gels applied on the stacks were prepared from sols composed of tetraethoxysilane, phosphorous oxychloride, boron tribromide, ethanol, HCl and water. Pastes prepared from the sols and solid fabricated through heat treatment of the sols at 1000°C were also used. The sols were applied on the stacks by the dip-coating method and the pastes were applied manually. The formed xerogels were heat-treated at temperatures of up to 1000°C. The MSFs of the grapefruit type were drawn from the stacks at a temperature of about 1900°C. Waveguiding properties of the fibers were examined under their excitation by an inclined collimated beam. It has been found that the sol-gel method is suitable particularly for filling-in the interstices at the end of the stack, which enables pressure control inside holes of the stack during MSF drawing.
- Published
- 2004
- Full Text
- View/download PDF
45. Synthesis and formation mechanism of cubic boron nitride nanorods in lithium bromide molten salt
- Author
-
Yingliang Liu, Yong Xiao, Mingtao Zheng, and Peng Wang
- Subjects
Materials science ,Lithium bromide ,Mechanical Engineering ,Inorganic chemistry ,Condensed Matter Physics ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Transmission electron microscopy ,Boron nitride ,Sodium amide ,General Materials Science ,Nanorod ,Boron tribromide ,Molten salt ,Selected area diffraction - Abstract
Cubic boron nitride nanorods (cBNNRs) were synthesized through a simple reaction between boron tribromide and sodium amide in lithium bromide molten salt medium at 600 °C in a sealed autoclave system. The cBNNRs observed by transmission electron microscopy have various diameters ranging from 8 to 25 nm with aspect ratios of about 10–20. X-ray diffraction and selected area electron diffraction pattern revealed the cubic phase of cBNNRs with a lattice constant a =3.625 A. The B:N ratio obtained by energy dispersive X-ray spectroscopy was 1:1.12, and Fourier transform infrared spectrum showed a characteristic absorption at 1106 cm –1 . The possible formation mechanism of cBNNRs in molten salt medium is also discussed.
- Published
- 2013
- Full Text
- View/download PDF
46. A Novel Route to Geminal Dibromocyclobutanes: Syntheses of 2-Substituted Cyclobutanone Acetals and Their Reaction with Boron Tribromide
- Author
-
Tore Nordvik and Udo H. Brinker
- Subjects
chemistry.chemical_classification ,Steric effects ,Ketone ,Geminal ,Organic Chemistry ,Acetal ,Halogenation ,General Medicine ,Medicinal chemistry ,Chemical synthesis ,Hydrolysis ,chemistry.chemical_compound ,chemistry ,Benzyl group ,Organic chemistry ,Boron tribromide ,Alkyl - Abstract
Nine 2-substituted cyclobutanone acetals, in addition to the parent cyclobutanone acetal, were synthesized from their corresponding cyclobutanones and subsequently treated with boron tribromide. The substituents were either alkyl chains or a phenyl and a benzyl group, respectively. The major compounds obtained in these reactions were, in most cases, the geminal dibromocyclobutanes which were obtained in yields between 50 and 73%. A 2-fold excess of BBr3 and a reaction time of 3 h at -78 degrees C afforded the best yields. In four cases no dibromide formation was observed at all, and the cyclobutanone acetals were hydrolyzed to the corresponding cyclobutanone. This is probably due to increased steric hindrance of the acetal and BBr3 in the transition state.
- Published
- 2003
- Full Text
- View/download PDF
47. Thetert-Butyl Moiety—A Base Resistent Thiol Protecting Group Smoothly Replaced by the Labile Acetyl Moiety
- Author
-
Nicolai Stuhr-Hansen
- Subjects
inorganic chemicals ,chemistry.chemical_classification ,Base (chemistry) ,Chemistry ,Aryl ,Organic Chemistry ,Medicinal chemistry ,chemistry.chemical_compound ,Acetyl chloride ,Thiol ,Organic chemistry ,Moiety ,Boron tribromide ,Protecting group ,Thioacetic acid - Abstract
Aryl t-butyl sulfides underwent quantitative tert-butyl/acetyl exchange reactions affording thioacetic acid S-aryl esters when treated with acetyl chloride and boron tribromide.
- Published
- 2003
- Full Text
- View/download PDF
48. Dealkylation with boron bromide chelates
- Author
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Sean Parkin, Lauren J. De Pue, Timothy S. Keizer, and David A. Atwood
- Subjects
chemistry.chemical_classification ,Chemistry ,Ligand ,Stereochemistry ,Organic Chemistry ,Alkylation ,Biochemistry ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Bromide ,Materials Chemistry ,Chelation ,Lewis acids and bases ,Boron tribromide ,Physical and Theoretical Chemistry ,Alkyl - Abstract
Potential two-point Lewis acid compounds can be formed by combining the salen( t Bu)H2 (N ,N ?-alkylenenebis(3,5-di-tertbutyl(2hydroxy)benzylidenimine) class of ligands and its derivatives with boron tribromide. In the present study compounds having the formula, L(BBr2)2 (L� /salen( t Bu) (1), salhen( t Bu) (2), L([ p tolyl]BBr) (L � /salen( t Bu) (3), salpen( t Bu) (4), salben( t Bu) (5), salhen( t Bu) (6), and t Bu-sal( t Bu)BBr2 (7) were prepared. These compounds are active towards the dealkylation of alkyl phosphates and are catalytic when stoichiometric amounts of BBr3 and trimethylphosphate are introduced to the chelate ligand. All of the compounds were characterized by Mp, elemental analysis, 1 H- and 11 B-NMR, IR, MS and in the case of 2 by X-ray crystallography.
- Published
- 2003
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- View/download PDF
49. A synthesis of the phenolic lipid, 3-[(Z)-pentadec-8-enyl] catechol, (15:1)-urushiol
- Author
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John H. P. Tyman, Brian G Schofield, and Choong H Khor
- Subjects
Catechol ,Plant Extracts ,Rhus ,Organic Chemistry ,Quinoline ,Catechols ,Ethyl acetate ,Cell Biology ,Toxicodendron ,Urushiol ,Lipids ,Biochemistry ,chemistry.chemical_compound ,chemistry ,Bromide ,Dermotoxins ,Organic chemistry ,Boron tribromide ,Molecular Biology ,Tetrahydrofuran ,Demethylation - Abstract
A synthesis of (15:1)-urushiol, urushiol monoene, 3-[(Z)-pentadec-8-enyl] catechol, 1,2-dihydroxy-3-[(Z)-pentadec-8-enyl] benzene, one of the toxic principles of Rhus toxicodendron and of Rhus vernicifera is described. 6-Chlorohexan-1-ol protected at the OH group with ethyl vinyl ether reacted with 2,3-dimethoxybenzaldehyde in the presence of lithium to give, after removal of the protective group with methanolic 4-toluenesulphonic acid, 1-(2,3-dimethoxyphenyl) heptane-1,7-diol. Catalytic hydrogenolysis in ethanol with palladium-carbon selectively afforded 7-(2,3-dimethoxyphenyl)heptane-1-ol accompanied by a small proportion of the 7-(3-methoxyphenyl)heptane-1-diol, formed by demethoxylation. Reaction of the dimethoxy compound with boron tribromide resulted in both bromination and demethylation to give 7-(2,3-dihydroxyphenyl) heptylbromide. This bromide in tetrahydrofuran (THF) containing hexamethylphosphoric triamide reacted with excess lithium oct-1-yne to give 3-(pentadec-8-enyl)catechol which, by catalytic hydrogenation in ethyl acetate containing quinoline, selectively formed the required cis product, 3-[(Z)-pentadec-8-enyl]catechol which was identical chromatographically and spectroscopically with urushiol monoene separated from the natural product.
- Published
- 2002
- Full Text
- View/download PDF
50. [Untitled]
- Author
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Mario Gleria and Roger De Jaeger
- Subjects
chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Thermosetting polymer ,Maleic anhydride ,02 engineering and technology ,Polymer ,Trimethylsilyl iodide ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vinyl polymer ,0104 chemical sciences ,Poly(dichlorophosphazene) ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Materials Chemistry ,Organic chemistry ,Boron tribromide ,0210 nano-technology ,Phosphazene - Abstract
This review reports research carried out by the authors during the last 10 years. The research involves the synthesis, characterization, functionalization, and possible utilization of cyclo- and polyphosphazenes. The investigations concern the synthesis of poly(dichlorophosphazene) by polycondensation reaction of dichlorophinoyliminotrichlorophosphorane; the grafting of unsaturated organic substrates (maleic anhydride, maleates or vinyl polymers) onto poly(organophosphazenes) by free radical reactions and the use of the synthesized materials for the preparation of new grafted copolymers or for the superficial modification of conventional organic macromolecules; the synthesis of phosphazenes containing free hydroxylic groups by reaction of methoxy aryloxy- or methoxy oligoethyleneoxy-substituted cyclo- and polyphosphazenes with boron tribromide or trimethylsilyl iodide and their use for the preparation of new phosphazene-based materials (e.g., sol-gel hybrids, thermosetting resins, azodyes, cyclolinear inorganic–organic polymers sometimes containing chiral units, or organic macromolecules having cyclophosphazene residues as pendant groups); and the preparation of oxazoline-containing cyclic and polymeric phosphazene derivatives for the synthesis of photoinitiators, chain extenders, or blend compatibilizers. The possible developments of this research are also envisaged.
- Published
- 2001
- Full Text
- View/download PDF
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