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1.
Dr. Bao‐Hua Xu Raul Alfonso Adler Yanez Hiroshi Nakatsuka Prof. Dr. Masato Kitamura Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《化学:亚洲杂志》2012,7(6):1347-1356
The frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 ( 1 ) reacts with an enolizable conjugated ynone by 1,4‐addition involving enolate tautomerization to give an eight‐membered zwitterionic heterocycle. The conjugated endione PhCO‐CH?CH‐COPh reacts with the intermolecular FLP tBu3P/B(C6F5)3 by a simple 1,4‐addition to an enone subunit. The same substrate undergoes a more complex reaction with the FLP 1 that involves internal acetal formation to give a heterobicyclic zwitterionic product. FLP 1 reacts with dimethyl maleate by selective overall addition to the C?C double bond to give a six‐membered heterocycle. It adds analogously to the triple bond of an acetylenic ester to give a similarly structured six‐membered heterocycle. The intermolecular FLP P(o‐tolyl)3/B(C6F5)3 reacts analogously with acetylenic ester by trans‐addition to the carbon–carbon triple bond. An excess of the intermolecular FLP tBu3P/B(C6F5)3, which contains a more nucleophilic phosphane, reacts differently with acetylenic ester examples, namely by O? C(alkyl) bond cleavage to give the {R‐CO2[B(C6F5)3]2?}[alkyl‐PtBu3+] salts. Simple aryl or alkyl esters react analogously by using the borane‐stabilized carboxylates as good leaving groups. All essential products were characterized by X‐ray diffraction. 相似文献
2.
Why Does the Intramolecular Trimethylene‐Bridged Frustrated Lewis Pair Mes2PCH2CH2CH2B(C6F5)2 Not Activate Dihydrogen?
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Thomas Özgün Dr. Ke‐Yin Ye Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5988-5995
The methyl labelled C3‐bridged frustrated phosphane borane Lewis pair (P/B FLP) 2 b was prepared by treatment of Mes2PCl with a methallyl Grignard reagent followed by anti‐Markovnikov hydroboration with Piers’ borane [HB(C6F5)2)]. The FLP 2 b is inactive toward dihydrogen under typical ambient conditions, in contrast to the C2‐ and C4‐bridged FLP analogues. Dynamic NMR spectroscopy showed that this was not due to kinetically hindered P???B dissociation of 2 b . DFT calculations showed that the hydrogen‐splitting reaction of the parent compound 2 a is markedly endergonic. The PH+/BH? H2‐splitting product of 2 b was indirectly synthesized by a sequence of H+/H? addition. It lost H2 at ambient conditions and confirmed the result of the DFT analysis. 相似文献
3.
Dr. Philipp Holtkamp Dr. Jan Schwabedissen Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Igor V. Koptyug Assoc. Prof. Dr. Vladimir V. Zhivonitko Prof. Dr. Norbert W. Mitzel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17381-17385
The reactivity of the frustrated Lewis pair (FLP) (F5C2)3SnCH2P(tBu)2 ( 1 ) was investigated with respect to the activation of elemental hydrogen. The reaction of 1 at elevated hydrogen pressure afforded the intramolecular phosphonium stannate(II) (F5C2)2SnCH2PH(tBu)2 ( 3 ). It was characterized by means of multinuclear NMR spectroscopy and single crystal X-ray diffraction. NMR experiments with the two isotopologues H2 and D2 showed it to be formed via an H2 adduct (F5C2)3HSnCH2PH(tBu)2 ( 2) and the subsequent formal reductive elimination of pentafluoroethane; this is supported by DFT calculations. Parahydrogen-induced polarization experiments revealed the formation of a second product of the reaction of 1 with H2, [HP(tBu)2Me][Sn(C2F5)3] ( 4 ), in 1H NMR spectra, whereas 2 was not detected due to its transient nature. 相似文献
4.
Dr. Alison C. McQuilken Quang Minh Dao Dr. Allan Jay P. Cardenas Dr. Jeffery A. Bertke Prof. Dr. Stefan Grimme Prof. Dr. Timothy H. Warren 《Angewandte Chemie (International ed. in English)》2016,55(46):14335-14339
We report a new class of frustrated Lewis pairs (FLPs) by the hydroboration of bulky isocyanates iPr2ArNCO (iPr2Ar=2,6‐iPr2C6H3) and Ph2tBuArNCO (Ph2tBuAr=2,6‐Ph2‐4‐tBuC6H2) with Piers’ borane (HB(C6F5)2). While hydroboration of smaller isocyanates such as iPr2ArNCO leads to isocyanate—N/B FLP adducts, hydroboration of the bulkier Ph2tBuArNCO allows isolation of the substrate‐free aminoborane with a short, covalent N?B bond. This confused FLP reversibly binds unsaturated substrates such as isocyanates and isocyanides, suggesting the intermediacy of a “normal” FLP along the reaction pathway, supported by high‐level DFT studies and variable‐temperature NMR spectroscopy. These results underscore the possibility of FLP behavior in systems that possess no obvious frustrated Lewis acid–base interaction. 相似文献
5.
Accessing Frustrated Lewis Pair Chemistry from a Spectroscopically Stable and Classical Lewis Acid‐Base Adduct
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Dr. Timothy C. Johnstone Gabriel N. J. H. Wee Prof. Dr. Douglas W. Stephan 《Angewandte Chemie (International ed. in English)》2018,57(20):5881-5884
B(C6F5)3 and P(MeNCH2CH2)3N form a classical Lewis adduct, (C6F5)3BP(MeNCH2CH2)3N. Although (C6F5)3BP(MeNCH2CH2)3N does not exhibit spectroscopic evidence of dissociation into its constituent acid and base, products of frustrated Lewis pair (FLP) addition reactions are seen with PhNCO, PhCH2N3, PhNSO, and CO2. Computational studies show that thermal access to the dissociated acid and base permits FLP reactivity to proceed. These results demonstrate that FLP reactivity extends across the entire continuum of equilibria governing Lewis acid‐base adducts. 相似文献
6.
Insertion Reactions of Neutral Phosphidozirconocene Complexes as a Convenient Entry into Frustrated Lewis Pair Territory
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Dr. Adrien T. Normand Dr. Gerald Kehr Prof. Pierre Le Gendre Prof. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):4285-4293
Neutral phosphidozirconocene complexes [Cp2Zr(PR2)Me] (Cp=cyclopentadienyl; 1a : R=cyclohexyl (Cy); 1b : R=mesityl (Mes); 1c : R=tBu) undergo insertion into the Zr?P bond by non‐enolisable carbonyl building blocks (O=CR′R′′), such as benzophenone, aldehydes, paraformaldehyde or CO2, to give [Cp2Zr(OCR′R′′PR2)Me] ( 3 – 7 ). Depending on the steric bulk around P, complexes 3 – 7 react with B(C6F5)3 to give O‐bridged cationic zirconocene dimers that display typical frustrated Lewis pair (FLP)/ambiphilic ligand behaviour. Thus, the reaction of {[Cp2Zr(μ‐OCHPhPCy2)][MeB(C6F5)3]}2 ( 10a ) with chalcone results in 1,4 addition of the Zr+/P FLP, whereas the reaction of {[Cp2Zr(μ‐OCHFcPCy2)][MeB(C6F5)3]}2 ( 11a ; Fc=(C5H4)CpFe) with [Pd(η3‐C3H5)Cl]2 yields the unique Zr?Fe?Pd trimetallic complex 13a , which has been characterised by XRD analysis. 相似文献
7.
Dr. Benedikt Waerder Martin Pieper Leif A. Körte Timo A. Kinder Dr. Andreas Mix Beate Neumann Dr. Hans‐Georg Stammler Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2015,54(45):13416-13419
Frustrated Lewis pairs (FLPs) have a great potential for activation of small molecules. Most known FLP systems are based on boron or aluminum atoms as acid functions, few on zinc, and only two on boron‐isoelectronic silicenium cation systems. The first FLP system based on a neutral silane, (C2F5)3SiCH2P(tBu)2 ( 1 ), was prepared from (C2F5)3SiCl with C2F5 groups of very high electronegativity and LiCH2P(tBu)2. 1 is capable of cleaving hydrogen, and adds CO2 and SO2. Hydrogen splitting was confirmed by H/D scrambling reactions. The structures of 1 , its CO2 and SO2 adducts, and a decomposition product with CO2 were elucidated by X‐ray diffraction. 相似文献
8.
B(C6F5)3‐Catalyzed Transfer Hydrogenation of Imines and Related Heteroarenes Using Cyclohexa‐1,4‐dienes as a Dihydrogen Source
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Dr. Indranil Chatterjee Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2015,54(6):1965-1968
The strong boron Lewis acid tris(pentafluorophenyl)borane, B(C6F5)3, is shown to abstract a hydride from suitably donor‐substituted cyclohexa‐1,4‐dienes, eventually releasing dihydrogen. This process is coupled with the FLP‐type (FLP=frustrated Lewis pair) hydrogenation of imines and nitrogen‐containing heteroarenes that are catalyzed by the same Lewis acid. The net reaction is a B(C6F5)3‐catalyzed, i.e., transition‐metal‐free, transfer hydrogenation using easy‐to‐access cyclohexa‐1,4‐dienes as reducing agents. Competing reaction pathways with or without the involvement of free dihydrogen are discussed. 相似文献
9.
Functionalization of Intramolecular Frustrated Lewis Pairs by 1,1‐Carboboration with Conjugated Enynes
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Dr. Andreas Feldmann Dr. Gerald Kehr Dr. Constantin G. Daniliuc Dr. Christian Mück‐Lichtenfeld Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(35):12456-12464
The vicinal P/B frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 undergoes 1,1‐carboboration reactions with the Me3Si‐substituted enynes to give ring‐enlarged functionalized C3‐bridged P/B FLPs. These serve as active FLPs in the activation of dihydrogen to give the respective zwitterionic [P]H+/[B]H? products. One such product shows activity as a metal‐free catalyst for the hydrogenation of enamines or a bulky imine. The ring‐enlarged FLPs contain dienylborane functionalities that undergo “bora‐Nazarov”‐type ring‐closing rearrangements upon photolysis. A DFT study had shown that the dienylborane cyclization of such systems itself is endothermic, but a subsequent C6F5 migration is very favorable. Furthermore, substituted 2,5‐dihydroborole products are derived from cyclization and C6F5 migration from the photolysis reaction. In the case of the six‐membered annulation product, a subsequent stereoisomerization reaction takes place and the resultant compound undergoes a P/B FLP 1,2‐addition reaction with a terminal alkyne with rearrangement. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(52):16815-16819
Diphenyldiazomethane reacts with HB(C6F5)2 and B(C6F5)3, resulting in 1,1‐hydroboration and adduct formation, respectively. The hydroboration proceeds via a concerted reaction involving initial formation of the Lewis adduct Ph2CN2BH(C6F5)2. The highly sensitive adduct Ph2CN2(B(C6F5)3) liberates N2 and generates Ph2CB(C6F5)3. DFT computations reveal that formation of Ph2CN2B(C6F5)3 from carbene, N2, and borane is thermodynamically favourable, suggesting steric frustration could preclude carbene–borane adduct formation and affect FLP‐N2 capture. 相似文献
11.
Daniel Winkelhaus Beate Neumann Dr. Hans‐Georg Stammler Dr. Raphael J. F. Berger Dr. Yuri V. Vishnevskiy Prof. Dr. Norbert W. Mitzel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9312-9320
The reaction of (C6F5)2BH ( 1 ) with N,N‐dimethylallylamine ( 2 ), N,N‐diethylallylamine ( 3 ) and 1‐allylpiperidine ( 4 ) afforded the five‐membered ring systems (C6F5)2B(CH2)3NR2 (R=Me ( 5 ), Et ( 6 )) and (C6F5)2B(CH2)3N(CH2)5 ( 7 ) with an intramolecular dative B? N bond. A different product was obtained from the reaction of (C6F5)2BH ( 1 ) with N,N‐diisopropylallylamine ( 8 ), which afforded the seven‐membered ring system (C6F5)2B(CH2)3N(iPr)CH(Me)CH2 ( 9 ) under extrusion of dihydrogen. All compounds were characterised by elemental analysis, NMR spectroscopy and single‐crystal X‐ray diffraction experiments. Density functional theory (DFT) studies were performed to rationalise the different reaction mechanism for the formation of products 6 and 9 . The bonding situation of compound 9 was analysed in terms of its electron density topology to describe the delocalised nature of a borane– enamine adduct. 相似文献
12.
Single‐Step Gas‐Phase Polyperfluoroalkylation of Naphthalene Leads to Thermodynamic Products
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Long K. San Eric V. Bukovsky Dr. Igor V. Kuvychko Dr. Alexey A. Popov Prof. Steven H. Strauss Dr. Olga V. Boltalina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4373-4379
High‐temperature gas‐phase, solvent‐ and catalyst‐free reaction of naphthalene with an excess of RFI reagent (RF?CF3, C2F5, n‐C3F7, and n‐C4F9) was used for the first time to produce a series of highly perfluoroalkylated naphthalene products NAPH(RF)n with n=2–5. Four 95+ % pure 1,3,5,7‐NAPH(RF)4 with RF?CF3, C2F5, n‐C3F7, and n‐C4F9 were isolated using a simple chromatography‐free procedure. These new compounds were fully characterized by 19F and 1H NMR spectroscopy, X‐ray crystallography (for RF?CF3 and C2F5), atmospheric‐pressure chemical ionization mass spectrometry, and cyclic and square‐wave voltammetry. DFT calculations confirm that the proposed synthesis yields the most stable isomers that have not been accessed by alternative preparation techniques. 相似文献
13.
Philipp Holtkamp Timo Glodde Dario Poier Beate Neumann Hans‐Georg Stammler Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2020,59(40):17388-17392
The geminal frustrated Lewis pair (F5C2)3SnCH2P(tBu)2 ( 1 ) reacted with N‐sulfinylaniline PhNSO to afford the first sulfur monoxide adduct of a main group metal, (F5C2)3SnCH2P(tBu)2?SO ( 2 ), which contains a SnCPSO ring. The second product is a phenylnitrene adduct of 1 . The surprising stability of 2 was compared with the stabilities of the so far inaccessible O2 and S2 adducts of 1 . Attempts to prepare these from 1 and the elemental chalcogens (O2, S8, Se∞, Te∞) led to four‐membered SnCPE ring systems. Quantum‐chemical investigations of 2 demonstrate the bond polarity of the SO unit to stabilize 2 . 相似文献
14.
Autoinduced Catalysis and Inverse Equilibrium Isotope Effect in the Frustrated Lewis Pair Catalyzed Hydrogenation of Imines
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Dipl.‐Chem. Sebastian Tussing Dr. Lutz Greb Dipl.‐Chem. Sergej Tamke Dr. Birgitta Schirmer Priv.‐Doz. Claudia Muhle‐Goll Prof. Dr. Burkhard Luy Prof. Dr. Jan Paradies 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8056-8059
The frustrated Lewis pair (FLP)‐catalyzed hydrogenation and deuteration of N‐benzylidene‐tert‐butylamine ( 2 ) was kinetically investigated by using the three boranes B(C6F5)3 ( 1 ), B(2,4,6‐F3‐C6H2)3 ( 4 ), and B(2,6‐F2‐C6H3)3 ( 5 ) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol?1) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect. 相似文献
15.
Alina D. Mironova Maxim A. Mikhajlov Taisiya S. Sukhikh Konstantin A. Brylev Artem L. Gushchin Ilia V. Eltsov Dmitri V. Stass Evgeny I. Goryunov Valery K. Brel Maxim N. Sokolov 《无机化学与普通化学杂志》2019,645(18-19):1135-1140
Reaction of [Mo6I8(CH3COO)6]2– with bis(pentafluorophenyl)phosphinic acid HO(O)P(C6F5)2 yielded a new bright‐red luminescent complex [{Mo6I8}(O2P(C6F5)2)6]2–, isolated as (Bu4N)(H5O2)[{Mo6I8}(O2P(C6F5)2)6] · 3(Et2O) · 1.5(acetone). It was characterized by X‐ray analysis, CV, ESI‐mass spectrometry, and NMR spectroscopy. 相似文献
16.
A Combined “Electrochemical–Frustrated Lewis Pair” Approach to Hydrogen Activation: Surface Catalytic Effects at Platinum Electrodes
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Elliot J. Lawrence Dr. Robin J. Blagg Dr. David L. Hughes Dr. Andrew E. Ashley Dr. Gregory G. Wildgoose 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):900-906
Herein, we extend our “combined electrochemical–frustrated Lewis pair” approach to include Pt electrode surfaces for the first time. We found that the voltammetric response of an electrochemical–frustrated Lewis pair (FLP) system involving the B(C6F5)3/[HB(C6F5)3]? redox couple exhibits a strong surface electrocatalytic effect at Pt electrodes. Using a combination of kinetic competition studies in the presence of a H atom scavenger, 6‐bromohexene, and by changing the steric bulk of the Lewis acid borane catalyst from B(C6F5)3 to B(C6Cl5)3, the mechanism of electrochemical–FLP reactions on Pt surfaces was shown to be dominated by hydrogen‐atom transfer (HAT) between Pt, [Pt?H] adatoms and transient [HB(C6F5)3] ? electrooxidation intermediates. These findings provide further insight into this new area of combining electrochemical and FLP reactions, and proffers additional avenues for exploration beyond energy generation, such as in electrosynthesis. 相似文献
17.
Dr. Dipendu Mandal Dr. Ting Chen Dr. Zheng-Wang Qu Prof. Dr. Stefan Grimme Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(53):e202201701
Reactions of PAr3/B(C6F5)3 (Ar=o-Tol, Mes, Ph) FLPs with diethyl azodicarboxylate (DEAD) afford the corresponding FLP addition products 1 – 3 in which P−N and B−O linkages are formed. In contrast, the reaction of BPh3, PPh3 and DEAD gave product 4 where P−N and N−B linkages were confirmed. In all cases, other binding modes were computed to be both higher in energy and readily distinguishable by 31P and 11B NMR parameters. These data illustrate the influence of steric demands and electronic structures on the nature of the products of FLP reactions with DEAD. 相似文献
18.
Chao Chen Florian Eweiner Birgit Wibbeling Roland Frhlich Shunsuke Senda Yasuhiro Ohki Kazuyuki Tatsumi Stefan Grimme Gerald Kehr Gerhard Erker 《化学:亚洲杂志》2010,5(10):2199-2208
The zirconocene complex [{(C6F5)2B‐(CH2)3‐Cp}(Cp‐PtBu2)ZrCl2] ( 6 ; Cp=cyclo‐C5H4) was prepared by hydroboration of [(allyl‐Cp)(Cp‐PtBu2)ZrCl2] ( 5 ) with HB(C6F5)2 (“Piers’ borane”). It represents a frustrated Lewis pair (FLP) in which both the Lewis acid and the Lewis base were attached at the metallocene framework. Its reaction with 1‐pentyne did not result in the 1,2‐addition of or deprotonation reaction by the FLP, but rather in the 1,1‐carboboration of the triple bond, thereby obtaining a Z/E mixture (1.2:1) of the respective organometallic substituted alkenes 7 . The analogous reaction of 1‐pentyne with the phosphorous‐free system [{(C6F5)2B‐(CH2)3‐Cp)}CpZrCl2] ( 9 ) gave the respective 1,1‐carboboration products ( Z‐10 / E‐10 ≈1.3:1). 相似文献
19.
Dr. Christoph Rosorius Jennifer Möricke Birgit Wibbeling Dr. Alison C. McQuilken Prof. Dr. Timothy H. Warren Dr. Constantin G. Daniliuc Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):1103-1113
The dimesitylpropargylphosphanes mes2P?CH2?C≡C?R 6 a (R=H), 6 b (R=CH3), 6 c (R=SiMe3) and the allene mes2P?C(CH3)=C=CH2 ( 8 ) were reacted with Piers’ borane, HB(C6F5)2. Compound 6 a gave mes2PCH2CH=CH(B(C6F5)2] ( 9 a ). In contrast, addition of HB(C6F5)2 to 6 b and 6 c gave mixtures of 9 b (R=CH3) and 9 c (R=SiMe3) with the regioisomers mes2P?CH2?C[B(C6F5)2]=CRH 2 b (R=CH3) and 2 c (R=SiMe3), respectively. Compounds 2 b , c underwent rapid phosphane/borane (P/B) frustrated Lewis pair (FLP) reactions under mild conditions. Compound 2 c reacted with nitric oxide (NO) to give the persistent FLP NO radical 11 . The systems 2 b , c cleaved dihydrogen at room temperature to give the respective phosphonium/hydridoborate products 13 b , c . Compound 13 c transferred the H+/H? pair to a small series of enamines. Compound 13 c was also a metal‐free catalyst (5 mol %) for the hydrogenation of the enamines. The allene 8 reacted with B(C6F5)3 to give the zwitterionic phosphonium/borate 17 . The ‐PPh2‐substituted mes2P‐propargyl system 6 d underwent a typical 1,2‐P/B‐addition reaction to the C≡C triple bond to form the phosphetium/borate zwitterion 20 . Several products were characterized by X‐ray diffraction. 相似文献
20.
Metal‐Free Hydrogenation Catalyzed by an Air‐Stable Borane: Use of Solvent as a Frustrated Lewis Base
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Daniel J. Scott Dr. Matthew J. Fuchter Dr. Andrew E. Ashley 《Angewandte Chemie (International ed. in English)》2014,53(38):10218-10222
In recent years ‘frustrated Lewis pairs’ (FLPs) have been shown to be effective metal‐free catalysts for the hydrogenation of many unsaturated substrates. Even so, limited functional‐group tolerance restricts the range of solvents in which FLP‐mediated reactions can be performed, with all FLP‐mediated hydrogenations reported to date carried out in non‐donor hydrocarbon or chlorinated solvents. Herein we report that the bulky Lewis acids B(C6Cl5)x(C6F5)3?x (x=0–3) are capable of heterolytic H2 activation in the strong‐donor solvent THF, in the absence of any additional Lewis base. This allows metal‐free catalytic hydrogenations to be performed in donor solvent media under mild conditions; these systems are particularly effective for the hydrogenation of weakly basic substrates, including the first examples of metal‐free catalytic hydrogenation of furan heterocycles. The air‐stability of the most effective borane, B(C6Cl5)(C6F5)2, makes this a practically simple reaction method. 相似文献