- Application of a Ferrocene-Based Palladacycle Precatalyst to Enantioselective Aryl-Aryl Kumada Coupling
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The palladium catalysed reaction of 1-iodo-2-methylnaphthalene and 2-methyl-1-naphthylmagnesium bromide gave quantitatively an (Sa)-configured cross-coupled product in 80 % e.e. using (R,Sp)-PPFA as a ligand. N,N-Dimethylaminomethylferrocene was cyclopalladated (Na2PdCl4, (S)?Ac?Phe?OH, 93 % e.e., as determined by 1H NMR as a result of self-induced non-equivalence), and the resulting (Sp)-configured dimeric palladacycle was employed as a precatalyst for this cross-coupling reaction (5 mol%). Addition to the palladacycle of diphenylphosphine and subsequent base-promoted bidentate ligand synthesis and palladium capture gave an in situ generated catalyst resulting in an (Sp)-configured product in up to 71 % e.e.
- Arthurs, Ross A.,Hughes, David L.,Richards, Christopher J.
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supporting information
(2022/02/21)
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- NOVEL CHIRAL DIHYDROBENZOAZAPHOSPHOLE LIGANDS AND SYNTHESIS THEREOF
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This invention relates to novel phosphorous ligands useful for organic transformations. Methods of making and using the ligands in organic synthesis are described. The invention also relates to processes for preparing the novel ligands.
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-
Paragraph 0145; 0146
(2018/06/15)
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- Computationally Assisted Mechanistic Investigation and Development of Pd-Catalyzed Asymmetric Suzuki-Miyaura and Negishi Cross-Coupling Reactions for Tetra- ortho-Substituted Biaryl Synthesis
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Metal-catalyzed cross-coupling reactions are extensively employed in both academia and industry for the synthesis of biaryl derivatives for applications to both medicine and material science. Application of these methods to prepare tetra-ortho-substituted
- Patel, Nitinchandra D.,Sieber, Joshua D.,Tcyrulnikov, Sergei,Simmons, Bryan J.,Rivalti, Daniel,Duvvuri, Krishnaja,Zhang, Yongda,Gao, Donghong A.,Fandrick, Keith R.,Haddad, Nizar,Lao, Kendricks So,Mangunuru, Hari P. R.,Biswas, Soumik,Qu, Bo,Grinberg, Nelu,Pennino, Scott,Lee, Heewon,Song, Jinhua J.,Gupton, B. Frank,Garg, Neil K.,Kozlowski, Marisa C.,Senanayake, Chris H.
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p. 10190 - 10209
(2018/10/20)
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- Supramolecular Polymerization of [5]Helicenes. Consequences of Self-Assembly on Configurational Stability
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The supramolecular polymerization of [5]helicenes 1 and 2 is investigated. The self-assembly of these helicenes proceeds by the operation of H-bonding interactions with a negligible participation of π-stacking. The enantiopurity of the sample has a dramatic effect on the supramolecular polymerization mechanism since it reverts the isodesmic mechanism for the racemic mixture to a cooperative one for the enantioenriched sample. Noticeably, the formation of supramolecular polymers efficiently increases the configurational stability of 1,14-unsubstituted [5]helicenes.
- Valera, Jorge S.,Gómez, Rafael,Sánchez, Luis
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p. 2020 - 2023
(2018/04/16)
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- A Binaphthyl-Based Scaffold for a Chiral Dirhodium(II) Biscarboxylate Ligand with α-Quaternary Carbon Centers
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A chiral dirhodium(II) paddlewheel complex has been synthesized from biscarboxylate ligands derived from BINOL, and the resulting complex has been used in enantioselective carbene/alkyne cascade reactions. The ligand design was guided by requirements of α
- Chen, Po-An,Setthakarn, Krit,May, Jeremy A.
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p. 6155 - 6161
(2017/09/15)
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- Readily available catalysts for demanding Suzuki–Miyaura couplings under mild conditions
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A straightforward synthesis of a sterically hindered and electron rich bidentate monophosphine biaryl ligand Sym-Phos of C,P-type of complexation was realised in a high yield starting from simple substrates in easily affordable conditions. In combination with a palladium source, the obtained ligand formed a highly active catalyst mediating sterically demanding Suzuki–Miyaura coupling reactions in aqueous media even at 60 °C and with no need to protect the reaction mixture by an inert gas.
- Demchuk, Oleg M.,Kap?on, Katarzyna,Mazur, Liliana,Strzelecka, Dorota,Pietrusiewicz, K. Micha?
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supporting information
p. 6668 - 6677
(2016/09/28)
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- Dimerization of Aryl Sulfonates by in situ Generated Nickel(0)
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A mild and user-friendly nickel-catalyzed method for the reductive homocoupling of aromatic tosylates is presented. The reaction proceeds between room temperature and 60 °C, with stable substrates (ArOTs) easily prepared from inexpensive and commercially available phenols or naphthols. It relies on a catalytic amount (10 mol%) of a robust catalyst (NiBr2bipy) that does not require the preparation of sensitive organometallic intermediates. Yields are good to excellent.
- Maddaluno, Jacques,Durandetti, Muriel
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supporting information
p. 2385 - 2388
(2015/10/19)
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- 2: A highly hindered pre-catalyst for the synthesis of tetra-ortho-substituted biaryls via Grignard reagent cross-coupling
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The new well-defined catalyst [Pd(μ-Cl)Cl(IPr*)]2 enables the efficient Grignard reagent cross-coupling for the synthesis of tetra-ortho-substituted biaryls. The high reactivity of the complex is associated with the important bulkiness of the I
- Lesieur, Mathieu,Slawin, Alexandra M. Z.,Cazin, Catherine S.J.
-
supporting information
p. 5586 - 5589
(2014/07/22)
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- Synthesis of axially chiral 1,1′-binaphthalenes by palladium-catalysed cross-coupling reactions of triorganoindium reagents
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1,1′-Binaphthalenes and heterocyclic analogues can be efficiently prepared by palladium-catalysed cross-coupling reactions between tri(1-naphthyl)indium reagents and 1-halonaphthalenes and haloisoquinolines. The reactions were usually carried out in THF at 80 °C with a slight excess of the indium reagent (40 mol-%) and a low catalyst loading (4 mol-% Pd) to afford the cross-coupling products in good yields (45-99 %). The method allows the synthesis of sterically hindered 2-substituted and 2,2′-disubstituted 1,1′-binaphthalenes and naphthylisoquinolines. In addition, the coupling reactions can be performed enantioselectively and the best enantiomeric excesses were obtained by using the chiral amino-phosphane ferrocenyl ligand (R,S)-PPFA. 1,1′-Binaphthalenes and heterocyclic derivatives have been synthesized by palladium-catalysed cross-coupling reactions between tri(1-naphthyl)indium reagents and 1-halonaphthalenes and haloisoquinolines, including 2-substituted and 2,2′-disubstituted 1,1′-binaphthyls. The coupling reactions can be performed enantioselectively in the presence of the chiral ligand (R,S)-PPFA. Copyright
- Mosquera, Angeles,Pena, Miguel A.,Sestelo, Jose Perez,Sarandeses, Luis A.
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p. 2555 - 2562
(2013/06/04)
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- Large yet flexible N-heterocyclic carbene ligands for palladium catalysis
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A straightforward and scalable eight-step synthesis of new N-heterocyclic carbenes (NHCs) has been developed from inexpensive and readily available 2-nitro-m-xylene. This process allows for the preparation of a novel class of NHCs coined ITent ("Tent" for "tentacular") of which the well-known IMes (N,N′-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IPr (N,N′-bis(2,6-di(2-propyl)phenyl)imidazol-2-ylidene) and IPent (N,N′-bis(2,6-di(3-pentyl)phenyl)imidazol-2-ylidene) NHCs are the simplest and already known congeners. The synthetic route was successfully used for the preparation of three members of the ITent family: IPent (N,N′-bis(2,6- di(3-pentyl)phenyl)imidazol-2-ylidene), IHept (N,N′-bis(2,6-di(4-heptyl) phenyl)imidazol-2-ylidene) and INon (N,N′-bis(2,6-di(5-nonyl)phenyl) imidazol-2-ylidene). The electronic and steric properties of each NHC were studied through the preparation of both nickel and palladium complexes. Finally the effect of these new ITent ligands in Pd-catalyzed Suzuki-Miyaura and Buchwald-Hartwig cross-couplings was investigated. Tentacular NHCs: A straightforward, scalable eight-step synthesis of N-heterocyclic carbenes (NHCs) has been developed using inexpensive and readily available 2-nitro-m-xylene, allowing the preparation of a class of NHCs designated ITent ("Tent" for "tentacular"). The electronic and steric properties of each NHC were studied through the preparation of both nickel and palladium complexes, and the effect of these new ITent ligands in Pd-catalyzed Suzuki-Miyaura and Buchwald-Hartwig cross-couplings was investigated.
- Meiries, Sebastien,Le Duc, Gaetan,Chartoire, Anthony,Collado, Alba,Speck, Klaus,Arachchige, Kasun S. Athukorala,Slawin, Alexandra M. Z.,Nolan, Steven P.
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supporting information
p. 17358 - 17368
(2014/01/06)
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- Planar chiral triazole-based phosphanes derived from [2.2]paracyclophane and their activity in suzuki coupling reactions
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In this communication we report the short synthesis of a variety of planar chiral triazole-based phosphanes. These molecules have been readily prepared from 4-azido[2.2]paracyclophane in two steps. It was observed that the stability of the resulting phosphanes was dependent on the C-4 substituent. The efficacy of the new phosphanes in the palladium-mediated Suzuki-Miyaura coupling reaction was evaluated. The phosphanes proved to be more effective than previously prepared planar chiral [2.2]paracyclophane-based phosphanes. Planar chiral phosphanes have been prepared from the first example of a [2.2]paracyclophane- derived 1,2,3-triazole with a carbon substituent at the 4-position. The nature of the 4-substituent appears to control the stability of the resulting 1,4,5-trisubstituted triazoles. The activities of the phosphanes as ligands in Suzuki coupling reactions has also been assessed. Copyright
- Glover, Jean E.,Martin, David J.,Plieger, Paul G.,Rowlands, Gareth J.
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p. 1671 - 1675
(2013/04/10)
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- Rhodium(II)-catalyzed cyclization of bis(N-tosylhydrazone)s: An efficient approach towards polycyclic aromatic compounds
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Ahead of the PAC: Polycyclic aromatic compounds (PACs) can be easily accessed by the combination of Suzuki-Miyaura cross-coupling and a [Rh 2(OAc)4]-catalyzed carbene reaction using easily available bis(N-tosylhydrazone)s as intermediates (see scheme; Ts=4-toluenesulfonyl). Copyright
- Xia, Ying,Liu, Zhenxing,Xiao, Qing,Qu, Peiyuan,Ge, Rui,Zhang, Yan,Wang, Jianbo
-
supporting information; experimental part
p. 5714 - 5717
(2012/07/28)
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- [PdA (IPr*) (cinnamyl)Cl]: An efficient pre-catalyst for the preparation of tetra-ortho-substituted biaryls by Suzuki-Miyaura cross-coupling
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The bigger the better: The new well-defined [Pd(IPr*)(cin)Cl] pre-catalyst is described (see scheme). This complex proves to be highly active in the Suzuki-Miyaura cross-coupling for the synthesis of tetra-ortho- substituted biaryls under mild conditions.
- Chartoire, Anthony,Lesieur, Mathieu,Falivene, Laura,Slawin, Alexandra M. Z.,Cavallo, Luigi,Cazin, Catherine S. J.,Nolan, Steven P.
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supporting information; experimental part
p. 4517 - 4521
(2012/05/04)
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- Synthesis of tetra-ortho-substituted biaryls using aryltriolborates
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Tetra-ortho-substituted biaryls were synthesized by cross-coupling between 2,6-disubstituted bromoarenes and aryltriolborates possessing substituents at ortho carbon. The use of a copper(I) halide such as CuCl (20 mol%) with a palladium catalyst was found
- Li, Gao-Qiang,Yamamoto, Yasunori,Miyaura, Norio
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supporting information; experimental part
p. 1769 - 1773
(2011/09/12)
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- Room-temperature synthesis of tetra-ortho-substituted biaryls by NHC-catalyzed Suzuki-Miyaura couplings
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Into the groove: The introduction of a C2-symmetric N-heterocyclic carbene ligand with appropriately substituted naphthyl side chains enables the efficient Suzuki-Miyaura coupling to form bulky tetra-ortho-substituted biaryls from aryl bromides and chlorides at room temperature. DFT calculations uncover the subtle steric phenomena at play that lead to the superior catalytic performance. Cyoct=cyclooctyl. Copyright
- Wu, Linglin,Drinkel, Emma,Gaggia, Fiona,Capolicchio, Samanta,Linden, Anthony,Falivene, Laura,Cavallo, Luigi,Dorta, Reto
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p. 12886 - 12890
(2011/12/15)
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- Pushing the limits of steric demand around a biaryl axis: Synthesis of tetra-ortho-substituted biaryl naphthalenes
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The synthesis of tetra-ortho-substituted biaryl naphthalenes, including examples bearing multiple ortho-isopropyl groups, has been developed via a catalytic rearrangement process.
- Glass, Adam C.,Klonoski, Sam,Zakharov, Lev N.,Liu, Shih-Yuan
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p. 286 - 288
(2011/03/18)
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- Ferrocenyl iminophosphine ligands in Pd-catalysed Suzuki couplings
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A mixture of Pd2(dba)3/{η-C5H 4CHN[CH(CH3)(Nap)]}Fe[η-C5H 4P(tBu)2] efficiently catalyzes the Suzuki reactions of a variety of bulky aryl halides and aryl- and alkyl-boronic acids, affording the desired cross-coupling biaryl products in quantitative isolated yields under mild conditions and at low (1 × 10-6-1 mol%) Pd loadings. Spectroscopic (NMR & ESI) analysis of the mixture of Pd 2(dba)3, the hybrid [P,N] ligands, and aryl halides revealed different structural forms of oxidative addition products that are dependent on the substituent on the imino nitrogen.
- Teo, Shihui,Weng, Zhiqiang,Hor, T.S. Andy
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experimental part
p. 2928 - 2934
(2011/08/05)
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- Highly active, well-defined (cyclopentadiene)(N-heterocyclic carbene)palladium chloride complexes for room-temperature Suzuki-Miyaura and Buchwald-Hartwig cross-coupling reactions of aryl chlorides and deboronation homocoupling of arylboronic acids
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A new class of well-defined N-heterocyclic carbene (NHC)-(cyclopentadiene) palladium chloride complexes such as CpPd(NHC)Cl wasw synthesized from the readily available starting NHC-palladium(II) chloride dimers. These air-stable, coordinatively saturated NHC-Pd complexes bearing the cyclopentadiene (Cp) unit exhibit high catalytic activity in the room temperature Suzuki-Miyaura and Buchwald-Hartwig cross-coupling reactions involving unactive aryl chlorides as the substrates. In addition, they are found to be extremely efficient catalysts in the deboronation homocoupling of arylboronic acids at room temperature.
- Jin, Zhong,Guo, Su-Xian,Gu, Xiao-Peng,Qiu, Ling-Ling,Song, Hai-Bing,Fang, Jian-Xin
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supporting information; experimental part
p. 1575 - 1585
(2011/02/28)
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- Efficient synthesis of chiral 1,1′-binaphthalenes by the asymmetric suzuki-miyaura reaction: Dramatic synthetic improvement by simple purification of naphthylboronic acids
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Naphthylboronic acids prepared as reported in the literature are contaminated with HCl. A very simple purification prior to their use in Suzuki-Miyaura couplings has been found to be crucial, rendering efficient some reactions that had been reported in th
- Genov, Miroslav,Almorin, Antonio,Espinet, Pablo
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p. 9346 - 9352
(2007/10/03)
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- Reductive ring opening of dihydrodibenzothiepine and dihydrodinaphtho- oxepine and -thiepine
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The 4,4′di-tert-butylbiphenyl (DTBB)-catalysed lithiation of dihydrodibenzothiepine (1) at -78°C for 30 min followed by reaction with a carbonyl compound [tBuCHO, Ph(CH2)2CHO, PhCHO, (n-C5H11)2/
- Foubelo, Francisco,Moreno, Benjamín,Soler, Tatiana,Yus, Miguel
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p. 9082 - 9096
(2007/10/03)
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- Short and efficient synthesis of coronene derivatives via ruthenium-catalyzed benzannulation protocol
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TpRuPPh3(CH3CN)2PF6 (3 mol %) was very active in catalytic benzannulation of 1-phenyl-2-ethynylbenzenes in dichloroethane (60 °C, 36 h) to afford phenanthrene in 95% yield. This method is applicable to the synthesis of various polycyclic aromatic hydrocarbons via two- and four-fold benzannulations, including various substituted coronene derivatives (53-86% yields) using this catalyst at a moderate loading (10 mol %).
- Shen, Hung-Chin,Tang, Jhih-Meng,Chang, Hsu-Kai,Yang, Chia-Wei,Liu, Rai-Shung
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p. 10113 - 10116
(2007/10/03)
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- Iron-catalyzed oxidative homo-coupling of aryl grignard reagents
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(Chemical Equation Presented) Iron-catalyzed homo-coupling of aryl Grignard reagents was successfully developed. A variety of aryl Grignard reagents were efficiently converted into the corresponding symmetrical biaryls in the presence of 1-5 mol % FeCl3 and a stoichiometric amount of 1,2-dichloroethane.
- Nagano, Takashi,Hayashi, Tamio
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p. 491 - 493
(2007/10/03)
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- Synthesis of chiral binaphthalenes using the asymmetric Suzuki reaction
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The synthesis of atropisomeric 1,1′-binaphthalenes can be achieved using an asymmetric Suzuki cross-coupling reaction. The Suzuki reaction leading to such hindered compounds is challenging and competing hydrolytic deboronation frequently dominates unless carefully chosen conditions are employed. The simple, standard mechanism is inadequate when describing the Suzuki coupling of hindered partners. Evidence suggests that the key step leading to asymmetry is transmetallation (delivery of the organometallic by the asymmetric ligand) and the reactions operate under kinetic control. Reductive elimination (itself likely to be triggered by oxidative addition of another molecule of halide) is fast compared with equilibration (epimerisation and/or cis-trans isomerisation).
- Cammidge, Andrew N.,Crépy, Karen V. L.
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p. 4377 - 4386
(2007/10/03)
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- Elaboration of a novel effective approach to enantiopure functionalised 2,2′-dialkyl-1,1′-binaphthyls by stereoconservative cross-couplings at positions 2 and 2′
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The yield and the stereochemical outcome of methylations of 1,1 ′-binaphthyl-2,2′-dielectrophiles (ditriflate and diiodide) clearly depend on the reactivity of the organometallics used. It was found that only the Negishi reaction of
- Kasák, Peter,Putala, Martin
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p. 5279 - 5282
(2007/10/03)
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- Reductive opening of 2,7-dihydrodinaphthoxepine and thiepine: Easy regioselective preparation of 2,2′-difunctionalised binaphthyls
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The lithiation of 2,7-dihydrodinaphthoheteroepines (5) with 2.2 equiv of lithium naphthalenide in THF at -78°C gives dianionic intermediates 8, which by reaction with different electrophiles [H2O, D2O, tBuCHO, Me2CO, Et2CO, (CH2) 4CO, (CH2)5CO] at the same temperature, followed by hydrolysis, leads to unsymmetrically 2,2′-disubstituted binaphthyls 6. When the lithiation is performed with an excess of lithium in the presence of a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 10 mol %), a double reductive cleavage takes place to give dianionic intermediate 9, which by reaction with different electrophiles [H2O, Me 2CO, Et2CO, (CH2)4CO, (CH 2)5CO], followed by hydrolysis with water, yields symmetrically 2,2′-disubstituted binaphthyls 7. In the case of starting from (R)-5a, the reductive opening by treatment with 2.2 equiv of lithium naphthalenide followed by reaction with H2O or (CH2) 5CO as electrophiles and final hydrolysis, leads to enantiomerically pure compounds (R)-6aa and (R)-6af, respectively.
- Foubelo, Francisco,Moreno, Benjamín,Yus, Miguel
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p. 8983 - 8986
(2007/10/03)
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- Process for the preparation of mono-, bi- or poly-functional biaryls
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A process for the preparation of mono-, bi- or poly-functional biaryls in the presence of a metal complex of the general formula IV as catalyst.
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Page column 8
(2008/06/13)
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- Chiral phosphorus cyclic compounds for transition metal-catalyzed asymmetric reactions
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Chiral phospholanes having biaryl chirality for applications in asymmetric catalysis are provided. A series of new chiral mono- or bidentate phosphorus ligands were efficiently prepared through a key intermediate (S)-4-chloro-4,5-dihydro-3H-4-phospha-cyclohepta[2,1-a;3,4-a′]binaphthalene and its derivatives. These ligands were complexed with transition metals to prepare catalysts, which were used in asymmetric catalytic reactions, such as, asymmetric hydrogenation, hydride transfer, allylic alkylation, hydrosilylation, hydroboration, hydrovinylation, hydroformylation, olefin metathesis, hydrocarboxylation, isomerization, cyclopropanation, Diels-Alder reaction, Heck reaction, isomerization, Aldol reaction, Michael addition; epoxidation, kinetic resolution or [m+n] cycloaddition wherein m=3 to 6 and n=2.
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- Chiral ligands, transition-metal complexes thereof and uses thereof in asymmetric reactions
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Chiral ligands and transition metal complexes based on such chiral ligands useful in asymmetric catalysis are disclosed. The chiral ligands include phospholanes, P,N ligands, N,N ligands, biphenols, and chelating phosphines. The ferrocene-based irridium (R,R)-f-binaphane complex reduces imines to the corresponding amines with 95-99.6% enantioselectivity and reduces β-substituted-α-arylenamides with 95% enantioselectivity. The transition metal complexes of the chiral ligands are useful in asymmetric reactions such as asymmetric hydrogenation of imines, asymmetric hydride transfer reactions, hydrosilylation, hydroboration, hydrovinylation, hydroformylation, allylic alkylation, cyclopropanation, Diels-Alder reaction, Heck reaction, isomerization, Aldol reaction, Michael addition and epoxidation reactions.
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-
- Synthesis of new chiral monodentate phosphines and their use in asymmetric hydrogenation
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A general synthesis of chiral 4,5-dihydro-3H-dinaphthophosphepines 1a-g is described. The resulting ligands represent a new class of monodentate chiral phosphines. First applications of 1a-g in the rhodium-catalyzed asymmetric hydrogenation of unsaturated
- Junge, Kathrin,Oehme, Günther,Monsees, Axel,Riermeier, Thomas,Dingerdissen, Uwe,Beller, Matthias
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p. 4977 - 4980
(2007/10/03)
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- 1,1′-Binaphthylazepine-based ligands for asymmetric catalysis. Part 1: Preparation and characterization of some new aminoalcohols and diamines
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Starting from (S)-1,1′-binaphthol, a series of ten novel enantiopure 1,1′-binaphthylazepine-based aminoalcohols and diamines 1a-1j were efficiently prepared and fully characterized. These derivatives, having either only an atropisomeric bridged-binaphthyl backbone or an additional stereogenic carbon center, can be interesting ligands for asymmetric catalysis.
- Mecca, Tommaso,Superchi, Stefano,Giorgio, Egidio,Rosini, Carlo
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p. 1225 - 1233
(2007/10/03)
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- trans-[PtCl2(Am)(C2H4)] and [PtCl3(C2H4)]-[AmH]+, containing binaphthyl secondary amines - Efficient chiral derivatizing agents for the enantiodiscrimination of chiral
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The complexes [PtCl3(C2H4)]-[AmH]+ and trans-[PtCl2(Am)(C2H4)], containing the binaphthyl secondary amine (S)-3,5-dihydro-4H-dinaphth[2,1-c:1′,2′-e]azepine, are effici
- Uccello-Barretta, Gloria,Bernardini, Raffaella,Balzano, Federica,Venturelli, Francesca,Caporusso, Anna Maria,Salvadori, Piero
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p. 3651 - 3655
(2007/10/03)
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- Study on the synthesis of nonracemic C2-symmetric 1,1′-binaphthyl-2,2′-diyl bridged ferrocene. Stereochemical result of the cross-coupling reactions controlled by Pd(II) or Pd(IV) complex intermediacy
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Palladium catalyzed Negishi, Suzuki and Stille cross-coupling reactions of enantiopure 2,2′-diiodo-1,1′-binaphthyl with the corresponding 1,1′-dimetalloferrocenes gave the C2-symmetric binaphthyl bridged ferrocene 1-1,1′-(1,1′-binaphthyl-2,2′-d
- Kasák,Miklá?,Putala
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p. 318 - 326
(2007/10/03)
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- The first asymmetric Suzuki cross-coupling reaction
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The first asymmetric coupling reactions between aryl halides and aryl boronates (Suzuki coupling) are described to give binaphthalene derivatives in up to 85% ee.
- Cammidge,Crepy
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p. 1723 - 1724
(2007/10/03)
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- First chelated chiral N-heterocyclic bis-carbene complexes
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First chiral bidentate bis-carbene complex of Pd(II) prepared from a bis-imidazolium salt derived from (S)-2,2′-bromomethyl-1,1′-binaphthyl exists in both cis- and trans-square planar geometry. These and the corresponding trans-Ni(II) complexes are remarkably resistant to high temperature, air, water, and silica gel chromatography. The Pd complexes catalyze Heck reactions.
- Clyne, Dean S.,Jin, Jian,Genest, Evan,Gallucci, Judith C.,RajanBabu
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p. 1125 - 1128
(2007/10/03)
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- Automated synthesis: Utilization of MEDLEY in synthetic processes
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A variety of reactions which are commonly used in synthetic chemistry are feasible with the automated synthesizer (MEDLEY). Air-sensitive organolithium and Grignard reagents as well as transition metal catalysts like Ni(0) and Pd(0) species are employable. The precise control of both the reaction temperature and the amount of added reagents enables to examine the dependence of chemical yields on the reaction temperature. Since the order of reagent addition is programmed and the reaction temperature is quickly tunable, sequential reactions can be conducted smoothly. An advanced control system was incorporated which allows a task to start immediately after the preceding one has finished. Owing to this function, the time for completing the multistep process can be minimized.
- Orita, Akihiro,Yasui, Yutaka,Otera, Junzo
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p. 337 - 341
(2013/08/07)
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- Synthesis of carbohelicenes and derivatives by 'carbenoid couplings'
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Short synthetic sequences to carbohelicenes have been achieved under thermal conditions, without using photochemistry and high dilution. Couplings of aromatic bis(bromomethyl) moieties, in the presence of an excess of LiHMDS, are key reactions in the final ring closures to carbohelicenes. These optimized, quick and efficient reactions occur at 0°C within 10 min. and often provide [5]-helicene, [5]-helicene derivatives and [7]-helicene in ~ 75% yield. Preliminary data questioned the formation of carbenoid anions and carbenes in the so called 'carbenoid couplings'.
- Gingras, Marc,Dubois, Fabien
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p. 1309 - 1312
(2007/10/03)
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- Syntheses of [5]-helicene by McMurry or carbenoid couplings
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Short syntheses of [5]-helicene have been accomplished under thermal conditions, without using photochemistry and high dilution. Key reactions comprised a Mcmurry coupling of a dialdehyde or a carbenoid-type coupling of aromatic bis(bromomethyl) moieties. The last coupling provide a 72% yield of [5]-helicene on a gram-scale (15 min O°C).
- Dubois, Fabien,Gingras, Marc
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p. 5039 - 5040
(2007/10/03)
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- Nickel- and Palladium-Catalyzed Homocoupling of Aryl Triflates. Scope, Limitation, and Mechanistic Aspects
-
Whereas the direct reduction of aryl triflates affords mainly phenols and some arenes, the presence of a catalytic amount of palladium or nickel results in the formation of biaryls. The homocoupling is performed in the presence of an electron source, either a cathode or zinc powder. A judicious choice of the metal (nickel or palladium), the ligand (monodentate or bidentate phosphine), and the reduction process (electrochemical or chemical) allows the synthesis of functional symmetrical biaryls. Nickel and palladium complexes ligated by bidentate ligands such as NiCl2(dppf) and Pd(OAc)2 + 1 BINAP are very efficient for the homocoupling of 1-naphthyl triflate, since the dimer was obtained in almost quantitative yield. However, the homocoupling is sensitive to steric hindrance, excluding for the moment the synthesis of atropisomers. The homocoupling proceeds via an activation of the C - O bond of the aryl triflate by a palladium(0) (or a nickel(0)) complex, providing an intermediate arylpalladium(II) (or nickel(II)) complex that after activation by electron transfer affords a new complex able to undergo a second oxidative addition with the aryl triflates.
- Jutand, Anny,Mosleh, Adil
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p. 261 - 274
(2007/10/03)
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- Process for preparing 1,1'-binaphthyls
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In the preparation of 1,1'-binaphthyls substituted in the 2,2'-positions (and optionally substituted in one or more of positions 3 to 7 and/or 3' to 7'), a 1-halo-2-substituted naphthalene is reacted with a 2-substituted-1-naphthyl-magnesium halide in the presence of a catalyst. The catalyst comprises palladium and a phosphine ligand. Typical phosphine ligands include triphenylphosphine, 1,4-bis(diphenylphosphino)butane, 2,2'-bis(diphenylphosphinomethoxy)-1,1'-binaphthyl, and tetrakis(triphonylphosphine).
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- Excited state carbon acid dissociation and competing photoarrangements of 5H-dibenzo[a,c]cycloheptene derivatives
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Structure reactivity studies of excited singlet state carbon acid dissociation and competing formal di-π-methane rearrangement have been carried out to gain more insights on the photochemistry displayed by these compounds. Photolysis in the presence of ethanolamine resulted in stereoselective deprotonation of the pseudo-axial proton. The results show that excited state carbon acid dissociation is a general reaction of dibenzo and dinaphtho cycloheptenes only if photochemical pathways are not competing.
- Budac,Wan
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p. 1447 - 1464
(2007/10/03)
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- Ni(0)-Catalyzed Cross Coupling of Aryl O-Carbamates and Aryl Triflates with Grignard Reagents. Directed Ortho Metalation-Aligned Synthetic Methods for Polysubstituted Aromatics via a 1,2-Dipole Equivalent
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The first Ni(0)-catalyzed cross-coupling reactions of aryl O-carbamates and aryl triflates with Grignard reagents (Scheme I) to give diversely polysubstituted aromatics 2d and 2e (Table I) which feature regiospecificity based on directed ortho metalation (carbamate), minimal β-hydride elimination (triflate), and dependence on steric and electronic effects are described.
- Sengupta, Saumitra,Leite, Magda,Raslan, Delio Soares,Quesnelle, Claude,Snieckus, Victor
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p. 4066 - 4068
(2007/10/02)
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- BINAPHTHYLCYCLOPENTADIENE: A C2-SYMMETRIC ANNULATED CYCLOPENTADIENYL LIGAND WITH AXIAL CHIRALITY
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The asymmetric preparation and metallation of binaphthylcyclopentadiene 1 is described.The key step in this four step synthesis is an asymmetric nickel-catalyzed coupling reaction.
- Colletti, Steven L.,Halterman, Ronald L.
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p. 3513 - 3516
(2007/10/02)
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- CHIRALITY TRANSFER FROM SILICON TO CARBON: USE OF OPTICALLY PURE CYCLIC SILANES WITH A BINAPHTHALENE CHIRAL UNIT
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The optically pure binaphthylic cyclic silanes R-6 and S-6 have been prepared and used in reductions and aldol condensations to achieve some of the highest ee's yet reported for chirality transfer with organosilanes.
- Jung, Michael E.,Hogan, Keith T.
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p. 6199 - 6202
(2007/10/02)
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- Erste asymmetrische Synthese β-binaphthylgestuetzter Silane, Stannane und Borane
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Starting with differently metallated 2,2'-dimethyl-1,1'-binaphthyls, various synthetic approaches to dihydrodinaphthoborepines (2) were attempted.As the borylation of the open chain derivetives (4a, b) did not succeed under cyclization, the (R)-dihydronaphthosilepine (5a) and the (R)- and (s)-dihydrodinaphthostannepines (7a) were prepared first, by starting from the enantiomerically pure bisbenzyllithium compounds (4a).The reaction of 5a with boron tribromide and of 7a with dichloroethylborane led exclusively to a halogen-methyl exchange reaction, to give the bromodihydrosilepine (5b) and the chlorodihydrostannepine (7b), while reaction of 7a with trichloroborane predominantly led to the formation of chlorodihydroborepine (2a).
- Gross, Ulrich-Maria,Bartels, Michael,Kaufmann, Dieter
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p. 277 - 284
(2007/10/02)
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- A zerovalent nickel-2,2'-bipyridine complex: an efficient catalyst for electrochemical homocoupling of ortho-substituted halides and their heterocoupling with meta- and para-substituted halides
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Electroreduction of ortho-substituted halides Ar-X in a nickel-2,2'-bipyridyl system and N-methylpyrrolidone as solvent gave the homocoupling product ArAr.The nickel-2,2'-bipyridyl system is also a catalyst for the electrochemical heterocoupling of ArX with meta- or para-substituted halides Ar'X'.
- Meyer, Gilbert,Rollin, Yolande,Perichon, Jacques
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p. 263 - 268
(2007/10/02)
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- Practical Synthesis of 1,1'-Binaphtyl-2-carboxylic Acids via Side Chain Oxidation of 2-Methyl-1,1'-binaphtyls
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Four 1,1'-binaphtyl-2-carboxylic acids were obtained in 38-53 percent isolated yield via three-stage oxidation of 2-methyl-1,1'-binaphtyls, that is, i) NBS-bromination to benzylic bromides, ii) treatment with sodium salt of 2-nitropropane to aldehydes, and iii) KMnO4-oxidation to carboxylic acids.
- Miyano, Sotaro,Okada, Shin-ichi,Suzuki, Toshiyuki,Handa, Shigeru,Hashimoto, Harukichi
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p. 2044 - 2046
(2007/10/02)
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