- Highly efficient palladacycle/dihydroimidazolium chloride system for the suzuki-miyaura cross-coupling of aryl halides (I, Br, Cl) with arylboronic acids
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A combination of a tertiary amine-based palladacycle and an N-heterocyclic carbene ligand precursor (1, N,N-bis-mesityl-4,5-dihydroimidazolium chloride) has been applied to catalyze the Suzuki-Miyaura cross-coupling of aryl halides with arylboronic acids. The substrate scope is general: a variety of electron rich and deficient aryl halides (I, Br, Cl) and arylboronic acids were found to undergo the cross-coupling reaction in good to excellent yields at low catalyst loading of 0.01-1 mol%. A combination of a tertiary amine-based palladacycle and an N-heterocyclic carbene ligand precursor has been applied to catalyze the Suzuki-Miyaura cross-coupling of aryl halides with arylboronic acids. Varieties of electron rich and deficient aryl halides (I, Br, Cl) and arylboronic acids were found to undergo the cross-coupling reaction in good to excellent yields at low catalyst loading of 0.01-1 mol%.
- Wang, Haiming,Wang, Jinping,Qiu, Wenwei,Yang, Fan,Liu, Xiaofeng,Tang, Jie
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Read Online
- An air stable carbene and mixed carbene 'dimers'
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The air-stable crystalline carbene 1,3-dimesityl-4,5-dichloroimidazol- 2-ylidene (2) is produced from the chlorination of 1,3-dimesityimidazol-2- ylidene (1) by 2 equiv of carbon tetrachloride. The physical and spectroscopic properties of the carbene are
- Arduengo III, Anthony J.,Davidson, Frederic,Dias,Goerlich, Jens R.,Khasnis, Dilip,Marshall, William J.,Prakasha
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Read Online
- Application of Quantitative 1H and 19F NMR to Organometallics
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Purity assessment of organometallics is particularly important for catalytic applications. While quantitative NMR is a well-known method in pharmaceutic chemistry, the present work illustrates its usefulness for the determination of the ligands and organometallics purities using proton and fluorine NMR. This method is fast, straightforward and provides accuracy results.
- Akhdar, Ayman,Andanson, Jean-Michel,Faure, Sophie,Gautier, Arnaud,Tra?kia, Mounir
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- Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors
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A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzyl-amines allowed us to obtain new Hoveyda–Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10?2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).
- Polyanskii, Kirill B.,Alekseeva, Kseniia A.,Raspertov, Pavel V.,Kumandin, Pavel A.,Nikitina, Eugeniya V.,Gurbanov, Atash V.,Zubkov, Fedor I.
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supporting information
p. 769 - 779
(2019/04/17)
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- Catalytic hydrogenation of α,β-unsaturated carboxylic acid derivatives using copper(i)/N-heterocyclic carbene complexes
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A simple and air-stable copper(i)/N-heterocyclic carbene complex enables the catalytic hydrogenation of enoates and enamides, hitherto unreactive substrates employing homogeneous copper catalysis and H2 as a terminal reducing agent. This atom economic transformation replaces commonly employed hydrosilanes and can also be carried out in an asymmetric fashion.
- Zimmermann, Birte M.,Kobosil, Sarah C. K.,Teichert, Johannes F.
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p. 2293 - 2296
(2019/02/27)
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- Cross-metathesis reaction of functionalized and substituted olefins using group 8 transition metal carbene complexes as metathesis catalysts
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The invention pertains to the use of Group 8 transition metal carbene complexes as catalysts for olefin cross-metathesis reactions. In particular, ruthenium and osmium alkylidene complexes substituted with an N-heterocyclic carbene ligand are used to catalyze cross-metathesis reactions to provide a variety of substituted and functionalized olefins, including phosphonate-substituted olefins, directly halogenated olefins, 1,1,2-trisubstituted olefins, and quaternary allylic olefins. The invention further provides a method for creating functional diversity using the aforementioned complexes to catalyze cross-metathesis reactions of a first olefinic reactant, which may or may not be substituted with a functional group, with each of a plurality of different olefinic reactants, which may or may not be substituted with functional groups, to give a plurality of structurally distinct olefinic products. The methodology of the invention is also useful in facilitating the stereoselective synthesis of 1,2-disubstituted olefins in the cis configuration.
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- Improved microwave synthesis of unsymmetrical N,N'-diaryl-1,2-aminoethane and imidazolidinium salts as precursors of N-heterocyclic carbenes
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Lithium aluminium hydride reduction of bis-unsymmetric-diaryloxamides 3 is difficult to accomplish especially for the sterically hindered mesityl derivative. Using microwaves LAH reduction of 3a,d was successful in a short time, however, with cleavage of the ether linkage to give compounds 11a,d. Extension of this method enabled the reduction of bis-oxamide derivatives 13 to the corresponding tetraamine derivative 14 which was then converted to the bis-imidazolidinium salt 15. Application of this method led to rapid reduction of unsymmetric N,N'-diaryloxamides 16 to the corresponding N,N'- diarylethylenediamines 17 which were converted to their corresponding imidazolidinium salts 18. the Partner Organisations 2014.
- Ibrahim, Yehia A.,Al-Awadi, Nouria A.,Al-Azemi, Talal F.,John, Elizabeth
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p. 38869 - 38876
(2014/11/08)
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- Continuous synthesis and use of N-heterocyclic carbene copper(I) complexes from insoluble Cu2O
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It is demonstrated that homogeneous N-heterocyclic carbene-copper(I)- chloride complexes can be prepared continuously by flowing NHC precursors through a packed bed of solid Cu2O suspended in molecular sieves. The method enables the synthesis o
- Opalka, Suzanne M.,Park, Jin Kyoon,Longstreet, Ashley R.,McQuade, D. Tyler
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supporting information
p. 996 - 999
(2013/04/10)
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- Oxygen-atom insertion of NHCecopper complex: The source of oxygen from N, N-dimethylformamide
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An unprecedented protocol for oxygen-atom insertion reaction of NHCecopper complexes has been developed by employing N,N-dimethylformamide as the oxygen source, which allows the preparation of imidazolinones from carbene complexes and decodes one of the m
- Zeng, Wei,Wang, Enyu,Qiu, Rui,Sohail, Muhammad,Wu, Shaoxiang,Chen, Fu-Xue
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- A direct and practical approach for the synthesis of N-heterocyclic carbene coinage metal complexes
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A novel direct and practical synthetic route leading to N-heterocyclic carbene coinage metal complexes has been developed by using air stable, commercial available Au(III) salt [MAuCl4·2H2O], CuCln (n=1,2) or AgCl, and imidazolium salts as starting materials. The reaction proceeded without sacrificing carbene transfer agent (Ag 2O) or using highly sensitive free NHC.
- Zhu, Shifa,Liang, Renxiao,Jiang, Huanfeng
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p. 7949 - 7955
(2012/09/22)
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- A direct and practical approach for the synthesis of Au(I)-NHC complexes from commercially available imidazolium salts and Au(III) salts
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A direct and practical approach for the synthesis of Au(I)-NHC complexes from imidazolium salts and commercially available aurate salt (MAuCl 4·2H2O) is described. The reaction proceeded without sacrificing carbene transfer agent (Ag
- Zhu, Shifa,Liang, Renxiao,Chen, Lijuan,Wang, Chao,Ren, Yanwei,Jiang, Huanfeng
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p. 815 - 818
(2012/03/10)
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- PKas of the conjugate acids of N-heterocyclic carbenes in water
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pKa values of 19.8-28.2 are reported for the conjugate acids of a large series of NHCs in water. The effects of ring size, N-substituent and C(4)-C(5) saturation on pKa are discussed.
- Higgins, Eleanor M.,Sherwood, Jennifer A.,Lindsay, Anita G.,Armstrong, James,Massey, Richard S.,Alder, Roger W.,O'Donoghue, Annmarie C.
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supporting information; experimental part
p. 1559 - 1561
(2011/03/22)
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- Switched stereocontrol in Grubbs - Hoveyda complex catalyzed ROMP utilizing proton-switched NHC ligands
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Grubbs-Hoveyda and Grubbs III type complexes with ferrocenyl- or -NEt 2-substituted NHC ligands were synthesized according to standard procedures. The electron donation of the NHC ligands in the respective ruthenium complexes can be modulated by oxidation of the ferrocenyl moiety or by protonation of the amino group. The neutral and the respective cationic (oxidized or protonated) ruthenium complexes were tested in the ROMP of norbornene. The change in the electron donation of the NHC ligands upon protonation leads to a significant change in the double-bond geometry (from E/Z ratio = 0.78 to E/Z = 1.04) and in the microstructure of the resulting polynorbornene. Consequently, addition of acid and protonation of the living catalyst attached to the polymer chain during the polymerization reaction allows fine-tuning the E/Z ratio of the resulting polynorbornene.
- Peeck, Lars H.,Leuthaeusser, Steffen,Plenio, Herbert
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scheme or table
p. 4339 - 4345
(2011/01/03)
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- PREPARATION OF SATURATED IMIDAZOLINIUM SALTS AND RELATED COMPOUNDS
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Methods for the preparation of saturated imidazolinium salts and related compounds that comprises reaction of formamidines with compounds such as dihaioethane and an optional base are disclosed. Alternatively, the imidazoünium salts and related compounds can be prepared in a one-step process without purification of the formamidine reactant. These methods make it possible to obtain numerous imidazolinium salts and related compounds under solvent-free reaction conditions and in excellent yields.
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Page/Page column 15; 19-20
(2009/06/27)
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- One-pot synthesis of unsymmetrical N-heterocyclic carbene ligands from N-(2-iodoethyl)arylamine salts
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Image Presented An approach that provides symmetrical, unsymmetrical, and asymmetric N-heterocyclic carbene (NHC) ligands is reported. Reaction of iodoethanol with aniline provides N-(2-iodoethyl)arylamine salts that are then converted to the corresponding iodide. Reaction with aliphatic or aromatic amines followed by triethyl orthoformate was used to provide 26 different NHC ligands.
- Bhanu Prasad,Gilbertson, Scott R.
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supporting information; experimental part
p. 3710 - 3713
(2011/02/28)
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- A facile preparation of imidazolinium chlorides
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A process for the preparation of symmetric and unsymmetric imidazolinium chlorides that involves reaction of a formamidine with dichloroethane and a base (a) is described. This method makes it possible to obtain numerous imidazolinium chlorides under solvent-free reaction conditions and in excellent yields with purification by simple filtration. Alternatively, symmetric imidazolinium chlorides can be prepared directly in moderate yields from substituted anilines by utilizing half of the formamidine Intermediate as sacrificial base (b).
- Kuhn, Kevin M.,Grubbs, Robert H.
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supporting information; experimental part
p. 2075 - 2077
(2009/04/10)
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- Probing the efficiency of N-heterocyclic carbene promoted O- to C-carboxyl transfer of oxazolyl carbonates
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(Chemical Equation Presented) Screening of a range of azolium salts, bases and solvents for reactivity indicates that triazolinylidenes, generated in situ with KHMDS in THF, promote the Steglich rearrangement of oxazolyl carbonates with high catalytic efficiency (typical reaction time 5 min at 1.5 mol % NHC). This protocol shows wide substrate applicability, even allowing the efficient generation of vicinal quaternary centers. An improved experimental procedure is also described that allows a simplified one-pot reaction protocol to be employed with similarly high catalytic efficiency.
- Thomson, Jennifer E.,Campbell, Craig D.,Concellon, Carmen,Duguet, Nicolas,Rix, Kathryn,Slawin, Alexandra M. Z.,Smith, Andrew D.
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p. 2784 - 2791
(2008/09/20)
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- Tuning the electronic properties of N-heterocyclic carbenes
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The electron-donating properties of N-heterocyclic carbenes ([N,N′-bis(2,6-dimethylphenyl)imidazol]-2-ylidene and the respective dihydro ligands) with 4,4′-R-substituted aryl rings (4,4′-R = NEt2, OC12H25, Me, H, Br, S(4-t
- Leuthaeusser, Steffen,Schwarz, Daniela,Plenio, Herbert
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p. 7195 - 7203
(2008/03/12)
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- trans-[1,3-Bis(2,4,6-trimethyl-phenyl)-imidazolidin-2-yl-idene] -dichlorido(triphenyl-phosphine-P)palladium(II)
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The title complex, [PdCl2(C21H26N2)(C18H15P)], shows slightly distorted square-planar coordination around the PdII metal centre. The Pd - C bond distance between the N-heterocyclic ligand and the metal atom is 2.028 (5) A. The dihedral angle be
- Sevincek, Resul,Tuerkmen, Hayati,Ayguen, Muhittin,Cetinkaya, Bekir,Garcia-Granda, Santiago
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p. m277-m279
(2008/03/11)
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- Microwave-assisted synthesis of N-heterocyclic carbene precursors
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A very simple and efficient procedure is reported for the synthesis of 1,3-diarylimidazolinium chlorides by cyclization of N,N′- diarylethylenediamines dihydrochlorides with triethyl orthoformate under microwave irradiation. Georg Thieme Verlag Stuttgart.
- Aidouni, Adila,Demonceau, Albert,Delaude, Lionel
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p. 493 - 495
(2007/10/03)
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- Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands
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This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR3)(Cl)2Ru=CHR′, which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)2(Cl)2Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H2IMes)(IMes)(Cl)2Ru=CHPh, and the other of (PCy3)(Cl)(CO)Ru[η2-(CH2- C6H2Me2)(N2 C3H4)(C6H2Me3)], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydridocarbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBut. We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.
- Trnka, Tina M.,Morgan, John P.,Sanford, Melanie S.,Wilhelm, Thomas E.,Scholl, Matthias,Choi, Tae-Lim,Ding, Sheng,Day, Michael W.,Grubbs, Robert H.
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p. 2546 - 2558
(2007/10/03)
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- High activity metal carbene metathesis catalysts generated using a thermally activated N-heterocyclic carbene precursor
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The invention provides a method for converting a less active or slower to initiate system to a higher activity system so that at the end of a polymerization the most active species is present in the system. The invention generally relates to a process for
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- Highly active metathesis catalysts generated in situ from inexpensive and air stable precursors
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The invention provides a process for the in-situ generation of a metathesis active catalyst of the formula: comprising contacting an NHC carbene with a dimer of the formula [(arene)MX1X]2 and an alkyne of the formula RC≡CR1 or RC≡EC—CR1 wherein M is ruthenium or osmium; X and X1 are the same or different and are each independently an anionic ligand; NHC is any N-heterocyclic carbene ligand; and, R and R1 are each independently hydrogen or a substituted or unsubstituted substituent selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl. Preferably, the NHC is an s-IMES or IMES carbene ligand; the arene is preferably p-cymene and the alkyne is preferably acetylene. The invention further provides a process for ROMP and RCM reactions using the metathesis active catalysts.
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- Amination reactions of aryl halides with nitrogen-containing reagents mediated by palladium/imidazolium salt systems
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Nucleophilic N-heterocyclic carbenes have been conveniently used as catalyst modifiers in amination reactions involving aryl chlorides, aryl bromides, and aryl iodides with various nitrogen-containing substrates. The scope of a coupling process using a Pd(0) or Pd(II) source and an imidazolium salt in the presence of a base, KOtBu or NaOH, was tested using various substrates. The Pd2(dba)3/IPr·HCl (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) system presents the highest activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand is also effective for the synthesis of benzophenone imines, which can be easily converted to the corresponding primary amines by acid hydrolysis. Less reactive indoles were converted to N-aryl-substituted indoles using as supporting ligand the more donating SIPr·HCl (5, SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene). The Pd(OAc)2/SIPr·HCl/NaOH system is efficient for the N-arylation of diverse indoles with aryl bromides. The general protocol developed has been applied successfully to the synthesis of a key intermediate in the synthesis of an important new antibiotic. Mechanistically, palladium-to-ligand ratio studies strongly support an active species bearing one nucleophilic carbene ligand.
- Grasa,Viciu,Huang,Nolan
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p. 7729 - 7737
(2007/10/03)
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- Imidazolylidenes, imidazolinylidenes and imidazolidines
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Starting from glyoxal, 1,3-diarylimidazolinium chlorides 3 were obtained in a three-step sequence via the diimines (1) and ethylene diamine dihydrochlorides (2). Reduction of 1,3-diarylimidazolinium chlorides (3) with lithium alumnium hydride furnished the 1,3- diarylimidazolidines (4) while their deprotonation with potassium hydride in thf gave access to stable carbenes (1,3-diarylimidazolin-2-ylidenes, 5). Similarly substituted imidazol-2-ylidenes are described for comparison.
- Arduengo III, Anthony J.,Krafczyk, Roland,Schmutzler, Reinhard,Craig, Hugh A.,Goerlich, Jens R.,Marshall, William J.,Unverzagt, Markus
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p. 14523 - 14534
(2007/10/03)
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