- Zinc catalysed electrophilic C-H borylation of heteroarenes
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Cationic zinc Lewis acids catalyse the C-H borylation of heteroarenes using pinacol borane (HBPin) or catechol borane (HBCat). An electrophile derived from [IDippZnEt][B(C6F5)4] (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) combined withN,N-dimethyl-p-toluidine (DMT) proved the most active in terms of C-H borylation scope and yield. Using this combination weakly activated heteroarenes, such as thiophene, were amenable to catalytic C-H borylation using HBCat. Competition reactions show these IDipp-zinc cations are highly oxophilic but less hydridophilic (relative to B(C6F5)3), and that borylation proceedsviaactivation of the hydroborane (and not the heteroarene) by a zinc electrophile. Based on DFT calculations this activation is proposed to proceed by coordination of a hydroborane oxygen to the zinc centre to generate a boron electrophile that effects C-H borylation. Thus, Lewis acid binding to oxygen sites of hydroboranes represents an under-developed route to access reactive borenium-type electrophiles for C-H borylation.
- Grundy, Matthew E.,Ingleson, Michael J.,Nichol, Gary S.,Yuan, Kang
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- C-H Borylation Catalysis of Heteroaromatics by a Rhenium Boryl Polyhydride
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Transition metal complexes bearing metal-boron bonds are of particular relevance to catalytic C-H borylation reactions, with iridium polyboryl and polyhydrido-boryl complexes the current benchmark catalysts for these transformations. Herein, we demonstrate that polyhydride boryl phosphine rhenium complexes are accessible and catalyze the C-H borylation of heteroaromatic substrates. Reaction of [K(DME)(18-c-6)][ReH4(Bpin)(ν2-HBpin)(κ2-H2Bpin)] 1 with 1,3-bis(diphenylphosphino)propane (dppp) produced [K(18-c-6)][ReH4(ν2-HBpin)(dppp)] 2 through substitution of two equivalents of HBpin, and protonation of 2 formed the neutral complex [ReH6(Bpin)(dppp)] 3. Combined X-ray crystallographic and DFT studies show that 2 is best described as a σ-borane complex, whereas 3 is a boryl complex. Significantly, the boryl complex 3 acted as a catalyst for the C(sp2)-H borylation of a variety of heteroarenes (14 examples including furan, thiophene, pyrrole and indole derivatives) and displayed similar reactivity to the iridium analogues.
- Donnelly, Liam J.,Faber, Teresa,Morrison, Carole A.,Nichol, Gary S.,Thomas, Stephen P.,Love, Jason B.
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p. 7394 - 7400
(2021/06/30)
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- Manganese-Catalyzed C(sp2)-H Borylation of Furan and Thiophene Derivatives
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Aryl boronic esters are bench-stable, platform building-blocks that can be accessed through metal-catalyzed aryl C(sp2)-H borylation reactions. C(sp2)-H bond functionalization reactions using rare- and precious-metal catalysts are well established, and while examples utilizing Earth-abundant alternatives have emerged, manganese catalysis remains lacking. The manganese-catalyzed C-H borylation of furan and thiophene derivatives is reported alongside an in situ activation method providing facile access to the active manganese hydride species. Mechanistic investigations showed that blue light irradiation directly affected catalysis by action at the metal center, that C(sp2)-H bond borylation occurs through a C-H metallation pathway, and that the reversible coordination of pinacolborane to the catalyst gave a manganese borohydride complex, which was as an off-cycle resting state.
- Britton, Luke,Skrodzki, Maciej,Nichol, Gary S.,Dominey, Andrew P.,Pawlu?, Piotr,Docherty, Jamie H.,Thomas, Stephen P.
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p. 6857 - 6864
(2021/06/28)
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- Isodesmic C-H Borylation: Perspectives and Proof of Concept of Transfer Borylation Catalysis
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The potential advantages of using arylboronic esters as boron sources in C-H borylation are discussed. The concept is showcased using commercially available 2-mercaptopyridine as a metal-free catalyst for the transfer borylation of heteroarenes using arylboronates as borylation agents. The catalysis shows a unique functional group tolerance among C-H borylation reactions, tolerating notably terminal alkene and alkyne functional groups. The mechanistic investigation is also described.
- Rochette, étienne,Desrosiers, Vincent,Soltani, Yashar,Fontaine, Frédéric-Georges
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supporting information
p. 12305 - 12311
(2019/08/20)
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- Alkylammoniotrifluoroborate functionalized polystyrenes: Polymeric pre-catalysts for the metal-free borylation of heteroarenes
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Three polymeric versions of ansa-N,N-dialkylammoniumtrifluoroborate ambiphilic molecules based on the styrene motif (poly(1-NMe2H+-2-BF3--4-styrene) (P-Me), poly(1-NEt2H+-2-BF3--4-styrene) (P-Et) and poly(1-piperidinyl-H+-2-BF3--4-styrene) (P-Pip)) were synthesized, characterized and tested as heterogeneous pre-catalysts for the borylation of electron-rich heteroarenes. These heterogeneous versions of previously reported pre-catalysts show similar reactivity patterns and represent the first examples of solid-supported FLP metal-free catalysts for the C-H borylation of heteroarenes.
- Bouchard, Nicolas,Fontaine, Frédéric-Georges
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supporting information
p. 4846 - 4856
(2019/04/17)
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- PRECATALYSTS AND PROCESS FOR THE METAL-FREE FUNCTIONALIZATION OF SP2 CARBONS USING THE SAME
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Precatalysts of formula I and IV, and processes for the functionalization of SP2-carbons using the same are described herein. The precatalysts comprise a fluoroborate salt protected intramolecular frustrated lewis pair (FLP). The precatalysts are bench stable with improved stability towards moisture and/or air. The precatalysts can be used to generate in situ the corresponding FLP catalyst.
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Paragraph 0185; 0186; 0196; 0197; 0198
(2018/10/24)
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- Practical and Scalable Synthesis of Borylated Heterocycles Using Bench-Stable Precursors of Metal-Free Lewis Pair Catalysts
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A practical and scalable metal-free catalytic method for the borylation and borylative dearomatization of heteroarenes has been developed. This synthetic method uses inexpensive and conveniently synthesizable bench-stable precatalysts of the form 1-NHR2-2-BF3-C6H4, commercially and synthetically accessible heteroarenes as substrates, and pinacolborane as the borylation reagent. The preparation of several borylated heterocycles on 2 and 50 g scales was achieved under solvent-free conditions without the use of Schlenk techniques or a glovebox. A kilogram-scale borylation of one of the heteroarene substrates was also achieved using this cost-effective green methodology to exemplify the fact that our methodology can be conveniently implemented in fine chemical industries.
- Jayaraman, Arumugam,Misal Castro, Luis C.,Fontaine, Frédéric-Georges
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supporting information
p. 1489 - 1499
(2018/10/26)
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- Metal-Free Borylation of Heteroarenes Using Ambiphilic Aminoboranes: On the Importance of Sterics in Frustrated Lewis Pair C-H Bond Activation
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Two novel frustrated Lewis pair (FLP) aminoboranes, (1-Pip-2-BH2-C6H4)2 (2; Pip = piperidyl) and (1-NEt2-2-BH2-C6H4)2 (3; NEt2 = diethylamino), were synthesized, and their structural features were elucidated both in solution and in the solid state. The reactivity of these species for the borylation of heteroarenes was investigated and compared to previously reported (1-TMP-2-BH2-C6H4)2 (1; TMP = tetramethylpiperidyl) and (1-NMe2-2-BH2-C6H4)2 (4; NMe2 = dimethylamino). It was shown that 2 and 3 are more active catalysts for the borylation of heteroarenes than the bulkier analogue 1. Kinetic studies and density functional theory calculations were performed with 1 and 2 to ascertain the influence of the amino group of this FLP-catalyzed transformation. The C-H activation step was found to be more facile with smaller amines at the expense of a more difficult dissociation of the dimeric species. The bench-stable fluoroborate salts of all catalysts (1F-4F) have been synthesized and tested for the borylation reaction. The new precatalysts 2F and 3F are showing higher reaction rates and yields for multigram-scale syntheses.
- Légaré Lavergne, Julien,Jayaraman, Arumugam,Misal Castro, Luis C.,Rochette, étienne,Fontaine, Frédéric-Georges
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supporting information
p. 14714 - 14723
(2017/10/25)
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- Synthetic Antenna Functioning As Light Harvester in the Whole Visible Region for Enhanced Hybrid Photosynthetic Reaction Centers
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The photosynthetic reaction center (RC) from the Rhodobacter sphaeroides bacterium has been covalently bioconjugated with a NIR-emitting fluorophore (AE800) whose synthesis was specifically tailored to act as artificial antenna harvesting light in the entire visible region. AE800 has a broad absorption spectrum with peaks centered in the absorption gaps of the RC and its emission overlaps the most intense RC absorption bands, ensuring a consistent increase of the protein optical cross section. The covalent hybrid AE800-RC is stable and fully functional. The energy collected by the artificial antenna is transferred to the protein via FRET mechanism, and the hybrid system outperforms by a noteworthy 30% the overall photochemical activity of the native protein under the entire range of visible light. This improvement in the optical characteristic of the photoenzyme demonstrates the effectiveness of the bioconjugation approach as a suitable route to new biohybrid materials for energy conversion, photocatalysis, and biosensing.
- Hassan Omar, Omar,La Gatta, Simona,Tangorra, Rocco Roberto,Milano, Francesco,Ragni, Roberta,Operamolla, Alessandra,Argazzi, Roberto,Chiorboli, Claudio,Agostiano, Angela,Trotta, Massimo,Farinola, Gianluca M.
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p. 1614 - 1623
(2016/08/02)
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- PROCESS FOR THE FUNCTIONALIZATION OF SP2-H CARBONS USING FRUSTRATED LEWIS PAIR CATALYSTS
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A catalytic process for the metal-free functionalization of sp2-carbons is described herein. The catalytic process is suitable for forming borylated alkenes, arenes and heteroarenes and comprises the use of catalysts comprising a Frustrated Lewis Pair (FLP).
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Paragraph 00103-00104; 00125-00127
(2016/11/14)
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- Metal-free catalytic C-H bond activation and borylation of heteroarenes
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Transition metal complexes are efficient catalysts for the C-H bond functionalization of heteroarenes to generate useful products for the pharmaceutical and agricultural industries. However, the costly need to remove potentially toxic trace metals from the end products has prompted great interest in developing metal-free catalysts that can mimic metallic systems.We demonstrated that the borane (1-TMP-2-BH2-C6H4)2 (TMP, 2,2,6,6-tetramethylpiperidine) can activate the C-H bonds of heteroarenes and catalyze the borylation of furans, pyrroles, and electron-rich thiophenes. The selectivities complement those observed with most transition metal catalysts reported for this transformation.
- Légaré, Marc-André,Courtemanche, Marc-André,Rochette, étienne,Fontaine, Frédéric-Georges
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p. 513 - 516
(2015/09/08)
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- Solvatochromism in diketopyrrolopyrrole derivatives: Experimental and computational studies
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A series of seven thiophen-substituted diketopyrrolopyrrole derivatives were synthesised and their solution absorption spectra characterised in a range of solvents of varying polarity. The absorption spectra of these diketopyrrolopyrrole derivatives exhibited significant negative solvatochromism. The behaviour is consistent with results of time-dependent density-functional theory calculations of excitation energies. Calculated electronic structures suggest that there is significant charge transfer between the electron-donating thiophen substituents and the diketopyrrolopyrrole core but that the magnitude of this charge shift is reduced in the excited state compared with the ground state. The resulting reduction in polarity of the excited state accounts for the negative solvatochromism observed. The implications of the results for the potential application of diketopyrrolopyrrole compounds as photovoltaic materials are considered.
- Szabadai, Rebecca S.,Roth-Barton, Jesse,Ghiggino, Kenneth P.,White, Jonathan M.,Wilson, David J. D.
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p. 1330 - 1337
(2014/11/08)
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- Synthesis of nitro- and amino-functionalized π-conjugated oligomers incorporating 3,4-ethylenedioxythiophene (EDOT) units
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Dissymmetric π-conjugated oligomers incorporating 3,4- ethylenedioxythiophene (EDOT) units and bearing nitro and amino end-groups were synthesized in good yields through Pd-catalyzed Suzuki coupling reactions and direct C-H bond arylation. Their spectrosc
- Trippé-Allard, Ga?lle,Lacroix, Jean-Christophe
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p. 861 - 866
(2013/07/27)
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- ORGANIC COMPOUNDS, PROCESS FOR PREPARING SAME AND USES IN ELECTRONICS
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The present disclosure relates to novel organic compounds, to the processes for preparing same and to the uses thereof, firstly in the electronics field, in particular in the fields referred to as plastic electronics and molecular electronics, and, secondly, in the coatings field, in particular in the fields of adhesion primers and intelligent coatings. The disclosure also relates to a material comprising a novel compound according to the invention.
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Paragraph 0148; 0150; 0155; 0156; 0157; 0158; 0159; 0160
(2013/04/10)
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- Synthetic routes to fluorescent dyes exhibiting large stokes shifts
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Derivatives of isomeric 2-(hydroxytolyl)-4,6-dimethylamino-1,3,5-triazines have been synthesized in high yields in a controlled manner using a multistep reaction sequence. Iodination of either 2-(1′-hydroxy-6′-methylphen- 2′-yl)- or 2-(1′-hydroxy-4′-methylphen-2′-yl)-4,6- dimethylamino-1,3,5-triazine with ICl provides species differing in the positioning of the iodo group relative to the hydroxyl which readily undergo Suzuki, Sonogashira, and Heck reactions under Pd(0) catalysis. Thus, thienyl, bisthienyl, and 3,4-ethylenedioxythienyl groups have been directly grafted, while unsubstituted polycyclic aromatics such as pyrene and perylene have been linked via alkyne bridges, as have ethynyldifluoroborondipyrromethane (BODIPY) dyes prepared in situ. The presence of a hydrogen bond in the ground state involving the hydroxyl substituent has been established by proton NMR and several X-ray structure determinations. All of the new dyes with a simple substituent (phenyl, thienyl) exhibited a pronounced green fluorescence resulting from an intramolecular proton transfer in the excited state (ESIPT) which produces a large Stokes shift (>10 000 cm-1). With other dyes, the fluorescence of the keto form responsible for the ESIPT process could be used as the input energy in efficient intramolecular energy transfer processes. Replacing perylene with pyrene allowed reversal of the direction of energy transfer from the polyaromatic module to the keto form.
- Rihn, Sandra,Retailleau, Pascal,De Nicola, Antoinette,Ulrich, Gilles,Ziessel, Raymond
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p. 8851 - 8863
(2013/01/15)
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- Chromium-thiophene-salen-based polymers for heterogeneous asymmetric hetero-Diels-Alder reactions
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New chiral thiophene-salen ligands have been synthesized and the corresponding chromium complexes proved to be efficient catalysts for promoting asymmetric hetero-Diels-Alder reactions with good activities and high enantio-selectivities (up to 88% ee). Th
- Zulauf, Anais,Mellah, Mohamed,Guillot, Regis,Schulz, Emmanuelle
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experimental part
p. 2118 - 2129
(2009/04/11)
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- Functionalizafion of 3,4-ethylenedioxythiophene
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Syntheses of 3,4-ethylenedioxythiophene-based vinylenes and oligomers are reported.
- Mohanakrishnan,Hucke, Andre,Lyon, Michael A.,Lakshmikantham,Cava, Michael P.
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p. 11745 - 11754
(2007/10/03)
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