- Palladium-Catalyzed Stereoselective Intramolecular Heck Dearomative Silylation of Indoles
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A palladium-catalyzed stereoselective intramolecular Heck dearomative of indoles with silyl termination has been developed. A type of tetracyclic indoline derivatives containing silicon were prepared, involving N-(2-bromobenzoyl)indoles and silylboronates. This protocol not only led to a broad substrate scope in acceptable yields but also could be scaled up to gram quantities as well as further synthetic transformation. (Figure presented.).
- Jin, Weiwei,Liu, Chenjiang,Liu, Tianxiang,Wang, Bin,Wang, Gang,Wei, Mingzhu,Xia, Yu,Zhang, Yonghong
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p. 909 - 913
(2022/01/28)
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- Generation of Axially Chiral Fluoroallenes through a Copper-Catalyzed Enantioselective β-Fluoride Elimination
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Herein we report the copper-catalyzed silylation of propargylic difluorides to generate axially chiral, tetrasubstituted monofluoroallenes in both good yields (27 examples >80%) and enantioselectivities (82-98% ee). Compared to previously reported synthetic routes to axially chiral allenes (ACAs) from prochiral substrates, a mechanistically distinct reaction has been developed: the enantiodiscrimination between enantiotopic fluorides to set an axial stereocenter. DFT calculations and vibrational circular dichroism (VCD) suggest that β-fluoride elimination from an alkenyl copper intermediate likely proceeds through a syn-β-fluoride elimination pathway rather than an anti-elimination pathway. The effects of the C1-symmetric Josiphos-derived ligand on reactivity and enantioselectivity were investigated. Not only does this report showcase that alkenyl copper species (like their alkyl counterparts) can undergo β-fluoride elimination, but this elimination can be achieved in an enantioselective fashion.
- Liu, Peng,Mai, Binh Khanh,Nafie, Jordan,O'Connor, Thomas J.,Toste, F. Dean
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supporting information
p. 13759 - 13768
(2021/09/07)
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- General Synthesis of Trialkyl-And Dialkylarylsilylboranes: Versatile Silicon Nucleophiles in Organic Synthesis
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Compared to carbon-based nucleophiles, the number of silicon-based nucleophiles that is currently available remains limited, which significantly hampers the structural diversity of synthetically accessible silicon-based molecules. Given the high synthetic
- Shishido, Ryosuke,Uesugi, Minami,Takahashi, Rikuro,Mita, Tsuyoshi,Ishiyama, Tatsuo,Kubota, Koji,Ito, Hajime
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supporting information
p. 14125 - 14133
(2020/09/16)
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- Nickel/copper-cocatalyzed decarbonylative silylation of acyl fluorides
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Ni/Cu-cocatalyzed decarbonylative silylation of acyl fluorides with silylboranes has been developed to afford various arylsilanes with high efficiency and good functional-group compatibility via carbon-fluorine bond cleavage and carbon-silicon bond formation. Such transformation can not only extend the functionalization type of acyl fluorides but complement the synthetic route for arylsilanes.
- Wang, Xiu,Wang, Zhenhua,Nishihara, Yasushi
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supporting information
p. 10507 - 10510
(2019/09/06)
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- Decarbonylative Silylation of Esters by Combined Nickel and Copper Catalysis for the Synthesis of Arylsilanes and Heteroarylsilanes
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An efficient nickel/copper-catalyzed decarbonylative silylation reaction of carboxylic acid esters with silylboranes is described. This reaction provides access to structurally diverse silanes with high efficiency and excellent functional-group tolerance
- Guo, Lin,Chatupheeraphat, Adisak,Rueping, Magnus
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supporting information
p. 11810 - 11813
(2016/11/16)
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- CuI/Pd0 cooperative dual catalysis: Tunable stereoselective construction of tetra-substituted alkenes
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This paper describes a tunable and stereoselective dual catalytic system that uses copper and palladium reagents. This cooperative silylcupration and palladium-catalyzed allylation readily affords trisubstituted alkenylsilanes. Fine-tuning the reaction conditions allows selective access to one stereoisomer over the other. This new methodology tolerates different substituents on both coupling partners with high levels of stereoselectivity. The one-pot reaction involving a CuI/Pd0 cooperative dual catalyst directly addresses the need to develop more time-efficient and less-wasteful synthetic pathways.
- Vercruysse, Sebastien,Cornelissen, Loic,Nahra, Fady,Collard, Laurent,Riant, Olivier
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supporting information
p. 1834 - 1838
(2014/03/21)
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- On the reactivity of silylboranes toward lewis bases: Heterolytic B-Si cleavage vs. adduct formation
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Silylboranes are important reagents in a variety of catalytic silylation and silaboration reactions. While transition-metal-catalyzed reactions are well established, organo-/Lewis base-catalyzed reactions of silylboranes have only recently emerged. For both catalytic processes the reactivity of silylboranes toward Lewis bases is of relevance. While for organo-catalyzed reactions Lewis base activation of the silylborane has been proposed, transition-metal- and especially copper-catalyzed reactions also frequently require the presence of Lewis basic alkali metal alkoxides. In the present study we explore the reaction of K(18-crown-6) tert-butoxide and the NHC 1,3-diisopropyl-4,5-dimethyl- imidazol-2-ylidene as exemplary Lewis bases with the two silylboranes pinB-SiMe2Ph and pinB-SiPh3 (pin = OCMe 2CMe2O). The reaction with K(18-crown-6) tert-butoxide results in activation of the boron-silicon bond. The isolated product of this activation is either the potassium silyl complex [K(18-crown-6)SiPh3] or [K(18-crown-6)(thf)2][pinB(SiMe2Ph)2], the formal Lewis acid/base adduct of [K(18-crown-6)SiMe2Ph] with pinB-SiMe2Ph. Both complexes react essentially as sources of nucleophilic silyl moieties in reactions with exemplary electrophiles. In contrast, usage of the carbene leads to the formation of isolable Lewis acid/base adducts of the type (NHC)pinB-SiR3, which do not react as sources of nucleophilic silyl moieties. The identification and characterization of these species appears of relevance for the mechanistic understanding and further development of Lewis base/organo- as well as transition-metal-catalyzed silyl transfer reactions. Copyright
- Kleeberg, Christian,Borner, Corinna
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p. 2799 - 2806
(2013/07/11)
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- Exceptionally E- and β-selective NHC-Cu-catalyzed proto-silyl additions to terminal alkynes and site- and enantioselective proto-boryl additions to the resulting vinylsilanes: Synthesis of enantiomerically enriched vicinal and geminal borosilanes
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An exceptionally site- and E-selective catalytic method for preparation of Si-containing alkenes through protosilylation of terminal alkynes is presented. Furthermore, the vinylsilanes obtained are used as substrates to generate vicinal or geminal borosilanes by another catalytic process; such products are derived from enantioselective protoborations of the Si-substituted alkenes. All transformations are catalyzed by N-heterocyclic carbene (NHC) copper complexes. Specifically, a commercially available imidazolinium salt, cheap CuCl (1.0 mol %) and Me2PhSi-B(pin), readily and inexpensively prepared in one vessel, are used to convert terminal alkynes to (E)-β-vinylsilanes efficiently (79-98 % yield) and in >98 % E and >98 % β-selectivity. Vinylsilanes are converted to borosilanes with 5.0 mol % of a chiral NHC-Cu complex in 33-94 % yield and up to 98.5:1.5 enantiomeric ratio (e.r.). Alkyl-substituted substrates afford vicinal borosilanes exclusively; aryl- and heteroaryl-substituted alkenes deliver the geminal isomers preferentially. Different classes of chiral NHCs give rise to high enantioselectivities in the two sets of transformations: C1-symmetric monodentate Cu complexes are most suitable for reactions of alkyl-containing vinylsilanes and bidentate sulfonate-bridged variants furnish the highest e.r. for substrates with an aryl substituent. Working models that account for the observed trends in selectivity are provided. Utility is demonstrated through application towards a formal enantioselective total synthesis of naturally occurring antibacterial agent bruguierol A. Different NHCs for different tasks: Three classes of N-heterocyclic carbene(NHC)-Cu complexes serve to promote two sets of reactions. Catalysts with an achiral monodentate NHC convert terminal alkynes to (E)-β-vinylsilanes with exceptional selectivity through efficient protosilylation. Cu-based catalysts bearing a chiral monodentate NHC bring about protoborations of alkyl-substituted vinylsilanes, generating enantiomerically enriched vicinal borosilanes; however, it is the sulfonate-bridged bidentate NHC-Cu complexes that deliver geminal silylborons with the highest e.r. values. Copyright
- Meng, Fanke,Jang, Hwanjong,Hoveyda, Amir H.
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supporting information
p. 3204 - 3214
(2013/03/28)
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- Copper-catalyzed addition of nucleophilic silicon to aldehydes
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How to train your silane: A new family of chiral copper(I) complexes that bear a bifluoride counteranion were prepared and used in the first example of the enantioselective transfer of a silyl group to an aldehyde. This procedure provides fast access to non-racemic α-hydroxysilanes in high enantioselectivities. Copyright
- Cirriez, Virginie,Rasson, Corentin,Hermant, Thomas,Petrignet, Julien,Diaz Alvarez, Jesus,Robeyns, Koen,Riant, Olivier
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supporting information
p. 1785 - 1788
(2013/04/10)
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- Synthesis of acylsilanes by copper(I)-catalyzed addition of silicon nucleophiles onto acid derivatives
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The transition metal-catalyzed transfer of silicon nucleophiles onto various electrophiles has recently gained considerable attention, due to the now readily available silicon pro-nucleophiles such as silylboronates. Our interest lies in the addition of such species to acid derivatives for the generation of acylsilanes. We report herein an efficient method to synthesize these compounds, starting from easy-to-form anhydrides, with very good yields. Copyright
- Cirriez, Virginie,Rasson, Corentin,Riant, Olivier
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supporting information
p. 3137 - 3140
(2013/12/04)
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- Synthesis of multisubstituted olefins through regio- and stereoselective silylborylation of an alkynylboronate/chemoselective cross-coupling sequences
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A highly regio- and stereoselective silylborylation of an alkynylboronate is disclosed. PhMe2Si-Bpin undergoes a Pd(OAc) 2/tOctNC-catalyzed syn-addition to the alkynylboronate to yield 1-phenyl-1-silyl-2,2-dibor
- Jiao, Jiao,Nakajima, Kiyohiko,Nishihara, Yasushi
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supporting information
p. 3294 - 3297
(2013/07/26)
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- Copper-catalysed domino silylative aldol reaction leading to stereocontrolled chiral quaternary carbons
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(Chemical Equation Presented) Asymmetric aldol reaction: A domino silylation-aldol reaction between enoyloxazolidinones and various aldehydes has been developed (see scheme). The process catalysed by a copper complex in the presence of a borosilane led to high diastereoselectivities. Yields between 59 and 90 % and d.r. values between 78:22 to 95:5 were obtained. When methacryloyloxazolidinones were used, a controlled chiral quaternary carbon was generated. BPin=4,4,5,5-tetramethyl-1,3,2dioxaborolan-2-yl.
- Welle, Alexandre,Petrignet, Julien,Tinant, Bernard,Wouters, Johan,Riant, Olivier
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supporting information; experimental part
p. 10980 - 10983
(2010/11/21)
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- Convenient preparation of silylboranes
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(Triorganosilyl)pinacolboranes were prepared by reaction of triorganosilyllithium reagents with pinacolborane or isopropoxypinacolborane in high yield. The reaction also is applicable to synthesis of 2-(triorganosilyl)-4,4,6-trimethyl-1,3,2-dioxaborinane. A new germylborane derivative was similarly prepared from the corresponding germyllithium.
- Suginome, Michinori
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p. 4647 - 4649
(2008/10/08)
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- Regio- and stereoselective synthesis of (Z)-β-silylalkenylboranes by silaboration of alkynes catalyzed by palladium and platinum complexes
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Addition of the silicon-boron bonds of (dimethylphenylsilyl)boranes having pinacol, catechol, and diethylamino groups on the boron across carbon- carbon triple bonds is effectively catalyzed by palladium complexes. The silaboration of a variety of terminal alkynes took place with almost complete regio- and stereoselectivity to afford (Z)-1-boryl-2-silylalkenes in high yields. The silaboration products were subjected to the palladium-catalyzed cross-coupling reaction with aryl iodide and rhodium-catalyzed conjugate addition to methyl vinyl ketone, giving β-silylstyrene derivatives and δ- silyl-γ,δ-unsaturated ketones, respectively, in high yields.
- Suginome, Michinori,Matsuda, Takanori,Nakamura, Hiroshi,Ito, Yoshihiko
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p. 8787 - 8800
(2007/10/03)
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- Regio- and stereo-selective silaboration of alkynes catalysed by palladium and platinum complexes
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Addition of the silicon-boron bond across carbon-carbon triple bonds, i.e. silaboration is most effectively catalysed by a palladium(0)-tert-alkyl isocyanide complex to give (Z)-1-boryl-2-silyl alkenes with high regio- and stereo-selectivity, which are useful for synthesis of stereodefined alkenylsilanes.
- Suginome, Michinori,Nakamura, Hiroshi,Ito, Yoshihiko
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p. 2777 - 2778
(2007/10/03)
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