- Asymmetric Bromine-Lithium Exchange: Application toward the Synthesis of New Biaryl-Diphosphine Ligands
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The desymmetrization of the prochiral tetrabromobiphenyl via asymmetric bromine-lithium exchange as a key step of synthesis of novel biphenyl-diphosphine ligands is reported. This new approach allows an easy access to twelve new enantiomerically pure atropisomeric ligands in one- to three-step reactions in good to excellent yields.
- Graff, Julien,?astawiecka, Elzbieta,Guénée, Laure,Leroux, Frédéric,Alexakis, Alexandre
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Read Online
- Synthesis and Physical Properties of Strained Doubly Phosphorus-Bridged Biaryls and Viologens
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New P/N-containing π-electron systems comprising fully planar biaryl arrays are synthesized by multiple radical phosphanylation. The biaryl moiety in these highly strained planar π-systems is rigidified by double P-bridging. The electronic properties of the core biaryl entity are varied by introducing N-donor substituents or by installing N-atoms within the π-system, thereby moving to the viologen core structure. The electrochemical and photophysical properties of these compounds are discussed and compared with those of related systems.
- Greulich, Tobias W.,Yamaguchi, Eriko,Doerenkamp, Carsten,Lübbesmeyer, Maximilian,Daniliuc, Constantin G.,Fukazawa, Aiko,Eckert, Hellmut,Yamaguchi, Shigehiro,Studer, Armido
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p. 6029 - 6033
(2017/05/08)
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- Synthetic method for optically pure double-helix oligomeric tetra-benzocyclooctene substances
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The invention discloses a synthetic method for optically pure double-helix oligomeric tetra-benzocyclooctene substances. The synthetic method comprises the following steps: (1) carrying out oxidative cross-coupling on diiodo dimethoxy biphenyl (51) and 2,2',6,6'-biphenyl tetrabromide (97) to obtain 1,16-dibromo-8,9-dimethoxy tetra-benzocyclooctene (96); (2) splitting the compound (96), thus obtaining optically pure (S, S)-96 and (R, R)-96; (3) taking the compound (96) as a raw material, synthesizing an intermediate (116) containing 6 benzene rings; (4) splitting the intermediate (116) to obtain (M)-116 and (P)-116; (5) making the optically pure (S, S)-96 and (M)-116 reacted to obtain target products, namely (M) -117, (M)-149 and (M)-150; and/or: making the (R, R)-96 and (P)-116 reacted to obtain target products, namely (P)-117, (P)-149 and (P)-150.
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- Catalytic asymmetric bromine-lithium exchange: A new tool to build axial chirality
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We present here the first catalytic desymmetrization of the 2,2′,6,6′-tetrabromobiphenyl 1 and analogues, by a bromine-lithium exchange catalyzed by either diamines or diether derivatives (0.5 equiv.), yielding axially chiral compounds in high yield (up to 89%) and high enantioselectivity (up to 82%).
- Perron, Quentin,Alexakis, Alexandre
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supporting information; experimental part
p. 2611 - 2620
(2011/01/05)
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- Drastic change in racemization barrier upon redox reactions: Novel chiral-memory units based on dynamic redox systems
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The helical configuration of dication dyes 22+ with a dihydrodibenzoxepin unit remained unchanged even at high temperature, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepin skeleton easily underwent racemization. Due to their electrochemical bistability, electron exchange between 1 and 22+ is prohibited. Thus, the above electrochromic pairs can serve as novel chiral-memory units where redox reactions trigger switching between an "erasable/writable"-state (1) and a "memorizing"-state (22+).
- Suzuki, Takanori,Wada, Kazuhisa,Ishigaki, Yusuke,Yoshimoto, Yasuyo,Ohta, Eisuke,Kawai, Hidetoshi,Fujiwara, Kenshu
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supporting information; scheme or table
p. 4100 - 4102
(2010/09/06)
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- PROCESS FOR THE SYNTHESIS OF 2,2',6-TRIBROMOBIPHENYL
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A process for the synthesis of 2,2′,6-tribromobiphenyl.
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Page/Page column 2
(2010/06/16)
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- Chiral bromine-lithium exchange catalyzed by diamines
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Different classes of prochiral polyhalide compounds have been tested in a chiral bromine-lithium exchange in the presence of different diamines with enantiomeric excesses of up to 63%.
- Perron, Quentin,Praz, Jezabel,Alexakis, Alexandre
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scheme or table
p. 1004 - 1007
(2009/10/23)
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- Process for the synthesis of 2,2 ,6-tribromobiphenyl
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A process for the synthesis of 2,2',6-tribromobiphenyl
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Page/Page column 4
(2008/06/13)
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- PROCESS FOR THE SYNTHESIS OF 2,2',6-TRIBROMOBIPHENYL
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A process for the synthesis of 2,2',6-tribromobiphenyl.
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Page/Page column 5-6
(2008/06/13)
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- PROCESS FOR THE PREPARATION OF ASYMMETRICALLY SUBSTITUTED BIARYLDIPHOSPHINES
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Provided is a process for the preparation of asymmetrically substituted biaryldiphosphine ligands of the formula, (I) wherein R1 is C1-6-alkyl or C3-10-cycloalkyl optionally substituted with one or more halogen atoms, and R2 and R3 are equal and are C5-10-cycloalkyl or C1-6-alkyl, or R2 is C5-10-cycloalkyl or C1-6-alkyl, and R3 is aryl optionally substituted with one or more substituents selected from the group consisting of halogen atoms, nitro, amino, C1-6-alkyl, C1-6-alkoxy and di-C1-6-alkylamino groups, and each C1-6-alkyl, C1-6-alkoxy, di-C1-6-alkylamino and C5-10-cycloalkyl group in R2 and R3 optionally being substituted with one or more halogen atoms, from 2,2’, 6, 6’-tetra-bromobiphenyl by a sequence of bromine-metal exchanges and subsequent reactions.
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Page/Page column 15
(2008/06/13)
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- PROCESS FOR THE PREPARATION OF ASYMMETRICALLY SUBSTITUTED BIARYLDIPHOSPHINES
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Provided is a process for the preparation of asymmetrically substituted biaryldiphosphine ligands of the formula (I), wherein R1 is C1-6-alkyl or C3-10-cycloalkyl optionally substituted with one or more halogen atoms, and R2 and R3 are equal and are selected from the group consisting of aryl, C5-10-cycloalkyl and C1-6-alkyl, or R2 is C5-10-cycloalkyl or C1-6-alkyl, and R3 is aryl optionally substituted with one or more substituents selected from the group consisting of halogen atoms, nitro, amino, C1-6-alkyl, C1-6-alkoxy and di-C1-6-alkylamino groups, and each C1-6-alkyl, C5-10-cycloalkyl, C1-6-alkoxy and di-C1-6-alkylamino group in R2 and R3 optionally being substituted with one or more halogen atoms, from 2,2’,6,6’-tetrabromobiphenyl by a sequence of brominemetal exchanges and subsequent reactions.
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Page/Page column 16
(2010/02/15)
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- Process for the preparation of asymmetrically substituted biaryldiphosphines
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Provided is a process for the preparation of asymmetrically substituted biaryldiphosphine ligands of the formula wherein R1 is C1-6-alkyl or C3-10-cycloalkyl optionally being substituted with one or more halogen atoms, and R2 and R3 are independently selected from the group consisting of aryl, C5-10-cycloalkyl and C1-6-alkyl, wherein each aryl moiety is optionally substituted with one or more substituents selected from the group consisting of halogen atoms, nitro, amino, C1-6-alkyl, C1-6-alkoxy and di-C1-6-alkylamino groups, and each C1-6-alkyl, C1-6-alkoxy, di-C1-6-alkylamino and C5-10-cycloalkyl group in R2 and R3 optionally being substituted with one or more halogen atoms, from 2,2',6,6'-tetrabromobiphenyl by a sequence of halogen-metal exchanges and subsequent reactions.
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Page/Page column 11
(2010/02/15)
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- Biphenylene dimer. Molecular fragment of a two-dimensional carbon net and double-stranded polymer
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Biphenylene dimers, which may be considered as 'macrocyclic' 2 x 2 fragments of net 1 and dimeric fragments of a double-stranded polymer, 5, are prepared. X-ray crystallography on two polymorphs of the dimer 9 reveals that its bond alternation is analogous to that in biphenylene; the tetraphenylene part of 9 has approximately C(2h) symmetry with a small dihedral angle (.-,M+ (M = Li, K) and 92-,2M+ (M = Li, K), were generated and characterized by ESR, NMR, and UV-vis spectroscopies. The spectral data for the dianions are compatible with classical structures; no evidence for 'in-plane aromaticity' is found. For polymer 5, a localized band and large density of states near the Fermi level are found, using extended Huckel theory calculations.
- Rajca, Andrzej,Safronov, Andrej,Rajca, Suchada,Ross II, Charles R.,Stezowski, John J.
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p. 7272 - 7279
(2007/10/03)
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