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Kazuaki Ishihara - One of the best experts on this subject based on the ideXlab platform.
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Boron Tribromide assisted chiral phosphoric acid catalysts for enantioselective 2 2 cycloaddition
2018Co-Authors: Tatsuhiro Sakamoto, Takuya Mochizuki, Yuta Goto, Manabu Hatano, Kazuaki IshiharaAbstract: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.
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Boron Tribromide-Assisted Chiral Phosphoric Acid Catalyst for a Highly Enantioselective Diels–Alder Reaction of 1,2-Dihydropyridines
2015Co-Authors: Manabu Hatano, Yuta Goto, Atsuto Izumiseki, Matsujiro Akakura, Kazuaki IshiharaAbstract: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
Neumann Beate - One of the best experts on this subject based on the ideXlab platform.
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Syntheses and structures of benzo-bis(1,3,2-diazaboroles) and acenaphtho-1,3,2-diazaboroles.
2019Co-Authors: Weber Lothar, Chrostowska Anna, Darrigan Clovis, Dargelos Alain, Stammler Hans-georg, Eickhoff Daniel, Neumann BeateAbstract:Weber L, Eickhoff D, Chrostowska A, et al. Syntheses and structures of benzo-bis(1,3,2-diazaboroles) and acenaphtho-1,3,2-diazaboroles. Dalton transactions (Cambridge, England : 2003). 2019;45(45):16911-16921.Colorless crystalline 2,6-dibromo-4,8-dimethyl-1,3,5,7-tetraphenylbenzobis(diazaborole) 4 resulted from the cyclocondensation of 3,6-dimethyl-1,2,4,5-tetraphenylaminobenzene 3d with two equivalents of Boron Tribromide in the presence of calcium hydride. Synthesis of the dark-red crystalline 2-bromo-N,N'-bis(diisopropylphenyl)acenaphtho-1,3,2-diazaborole 7 was effected by the cyclocondensation of 1,2-bis(N-2',6'-diisopropylphenylimino)acenaphthene (5) and Boron Tribromide with subsequent sodium amalgam reduction of the initially formed burgundy red diazaborolium salt 6. Compounds 4, 6 and 7 are characterised by elemental analyses, 1H, 11B and 13C NMR spectroscopy, as well as by single X-ray diffraction studies. The electronic structures of 4, 6 and 7 are subject to DFT calculations
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Syntheses and structures of benzo-bis(1,3,2-diazaboroles) and acenaphtho-1,3,2-diazaboroles
2019Co-Authors: Weber Lothar, Chrostowska Anna, Darrigan Clovis, Dargelos Alain, Stammler Hans-georg, Eickhoff Daniel, Neumann BeateAbstract:International audienceColorless crystalline 2,6-dibromo-4,8-dimethyl-1,3,5,7-tetraphenylbenzobis(diazaborole) 4 resulted from the cyclocondensation of 3,6-dimethyl-1,2,4,5-tetraphenylaminobenzene 3d with two equivalents of Boron Tribromide in the presence of calcium hydride. Synthesis of the dark-red crystalline 2-bromo-N,N’-bis(diisopropylphenyl)acenaphtho-1,3,2-diazaborole 7 was effected by the cyclocondensation of 1,2-bis(N-2’,6’-diisopropylphenylimino)acenaphthene (5) and Boron Tribromide with subsequent sodium amalgam reduction of the initially formed burgundy red diazaborolium salt 6. Compounds 4, 6 and 7 are characterised by elemental analyses, 1H, 11B and 13C NMR spectroscopy, as well as by single X-ray diffraction studies. The electronic structures of 4, 6 and 7 are subject to DFT calculations
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Tris(perfluorotolyl)borane-A Boron Lewis Superacid
2017Co-Authors: Körte, Leif Arne, Stammler Hans-georg, Neumann Beate, Schwabedissen Jan, Soffner Marcel, Blomeyer Sebastian, Reuter Christian, Vishnevskiy Yury, Mitzel, Norbert W.Abstract:Körte LA, Schwabedissen J, Soffner M, et al. Tris(perfluorotolyl)borane-A Boron Lewis Superacid. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION. 2017;56(29):8578-8582.Tris[tetrafluoro-4-(trifluoromethyl)phenyl] borane (BTolF) was prepared by treating Boron Tribromide with tetrameric F3CC6F4-Cu-I. The F3CC6F4-CuI was generated from F3CC6F4MgBr and copper(I) bromide. Lewis acidities of BTolF evaluated by the Gutmann-Beckett method and calculated fluoride-ion affinities are 9 and 10%, respectively, higher than that of tris(pentafluorophenyl) borane (BCF) and even higher than that of SbF5. The molecular structures of BTolF and BCF were determined by gas-phase electron diffraction, that of BTolF also by single-crystal X-ray diffraction
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1,3,2-Benzodiazaboroles with 1,3-Pentafluorophenyl and Tetrafluoropyridyl Substituents as Building Blocks in Luminescent Compounds
2013Co-Authors: Weber Lothar, Halama Johannes, Böhling Lena, Brockhinke Andreas, Chrostowska Anna, Darrigan Clovis, Dargelos Alain, Stammler Hans-georg, Neumann BeateAbstract:Weber L, Halama J, Böhling L, et al. 1,3,2-Benzodiazaboroles with 1,3-Pentafluorophenyl and Tetrafluoropyridyl Substituents as Building Blocks in Luminescent Compounds. European Journal of Inorganic Chemistry. 2013;2013(24):4268-4279.The reaction of N-4-trimethylsilylphenyl-3,6-di-tert-butylcarbazole (3) or N-5-trimethylsilylthien-2-yl-3,6-di-tert-butylcarbazole (4) with Boron Tribromide and subsequently with triphenylphosphane afforded the dibromoborylphenylcarbazole-phosphane adduct 5 or its thiophene derivative 6 as colorless solids. These adducts were converted into the new benzodiazaborole derivatives 7 and 8 by treatment with N,N-bis(pentafluorophenyl)-o-phenylenediamine (1) and 2,2,6,6-tetramethylpiperidine in hot toluene (52 or 45% yield). The analogous compounds 9 and 10 were obtained by condensing precursors 5 and 6 with bis(N,N-2,3,5,6-tetrafluoropyrid-4-yl)-o-phenylenediamine (2) in the presence of the piperidine derivative in 35 and 16% yield. Compounds 7-10 were characterized by NMR spectroscopy (H-1, B-11, C-13, F-19) and mass spectrometry. The molecular structure of 8 was elucidated by X-ray diffraction analysis. The borylated systems show intense blue luminescence upon UV irradiation
Peter Langer - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of benzofurans with remote bromide functionality by domino "ring-cleavage-deprotection-cyclization" reactions of 2-alkylidenetetrahydrofurans with Boron Tribromide.
2005Co-Authors: Esen Bellur, Peter LangerAbstract:[reaction: see text] Bromination and subsequent Suzuki reactions of 2-alkylidenetetrahydrofurans, readily available by [3+2] cyclizations, afforded 1'-(2''-methoxyphenyl)-2-alkylidenetetrahydrofurans. Treatment of the latter with Boron Tribromide and subsequent addition of water resulted in the chemoselective formation of functionalized benzofurans containing a remote bromide functionality. The products are formed by a new domino "ring-cleavage-deprotection-cyclization" reaction. The addition of an aqueous solution of potassium tert-butoxide, rather than water, afforded saturated analogues of calycine by a "ring-cleavage-deprotection-ring-closure-lactonization" reaction.
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reaction of 2 alkylidenetetrahydrofurans with Boron Tribromide chemo and regioselective synthesis of 6 bromo 3 oxoalkanoates by application of a cyclization ring opening strategy
2004Co-Authors: Esen Bellur, Peter LangerAbstract:Bromo-3-oxoalkanoates, benzofurans and 1,7-dibro- moheptan-4-ones were chemo- and regioselectively prepared by reaction of 2-alkylidenetetrahydrofurans with Boron Tribromide.
Philippe Cotelle - One of the best experts on this subject based on the ideXlab platform.
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antioxidant properties of 3 hydroxycoumarin derivatives
2004Co-Authors: Fabrice Bailly, Cedric Maurin, Elisabeth Teissier, Herve Vezin, Philippe CotelleAbstract:A series of hydroxylated 3-hydroxycoumarins was synthesised by the reaction of 3-aryl-2-hydroxypropenoic derivatives with Boron Tribromide. They were evaluated for their ability to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical, the superoxide anion radical, the hydroxyl radical and the peroxynitrite anion and to inhibit copper-induced human LDL peroxidation. The physicochemical results were in accordance to establish the compounds hydroxylated on C-6 and C-7 positions as the most active of the series with antioxidant potencies comparable to those of quercetin and vitamin C. These compounds form o- and p-quinonoid derivatives upon radical scavenging and may serve as new lead compounds for pharmacological investigations.
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reaction of aryl 2 hydroxypropenoic derivatives with Boron Tribromide
2001Co-Authors: Romain Dupont, Philippe CotelleAbstract:Abstract ( Z )-Mono, di or trimethoxyphenyl-2-hydroxypropenoic acids 1a–d gave mixtures of ( E ) and ( Z ) mono, di or trihydroxyphenyl-2-hydroxypropenoic acids 2a–d when treated with Boron Tribromide. The isomerisation proceeds during the work-up and depends on the duration of the hydrolysis and the number of oxygens on the aromatic ring. When the aromatic ring was substituted with a methoxy group at the ortho position, a cyclisation occurs, and 3-hydroxycoumarins 3 and benzofuran-2-carboxylic acids 4 can be obtained. 3-Hydroxycoumarin 3a can also be obtained almost quantitatively from the reaction of methyl 3-(2-methoxyphenyl)-2,3-epoxypropanoate with Boron Tribromide.
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reaction of arylethanals with Boron Tribromide
1998Co-Authors: Romain Dupont, Philippe CotelleAbstract:Abstract Treatment of arylethanals 1 with Boron Tribromide give 2-phenylnaphthalenes 2 or 1,2,9,10-tetrahydro-1,9-epoxydibenzo[a,e]cyclooctenes 3 by a tandem aldol condensation-intramolecular Friedel-Crafts cyclization or a condensation at the O-position followed by a double Friedel-Crafts alkylation respectively. In all cases, a total demethylation of the methoxy groups occurs.
Tatsuhiro Sakamoto - One of the best experts on this subject based on the ideXlab platform.
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Boron Tribromide assisted chiral phosphoric acid catalysts for enantioselective 2 2 cycloaddition
2018Co-Authors: Tatsuhiro Sakamoto, Takuya Mochizuki, Yuta Goto, Manabu Hatano, Kazuaki IshiharaAbstract: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.