A Short Way to Switchable Carbenes

Hashmi, A. Stephen K.; Lothschütz, Christian; Graf, Katharina; Häffner, Tobias; Schuster, Andreas; Röminger, Frank

doi:10.1002/adsc.201100183

Cited by 116 publications

(74 citation statements)

References 32 publications

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“…Thes tarting point of our studyw as the synthesiso f five-membered NHC gold(I) chloride complexes.B y following our previously reported synthetic strategies (Scheme 1), [9][10][11][12] twelve different unsymmetrical NHOCs, saturated and unsaturated NHC gold(I) complexes as well as one saturated six-membered ring and one nitrogen acyclic carbene (NAC)c omplex were synthesized( Scheme2). In order to compare the results,o no ne nitrogen atom the 2,6-diisopropylphenyl group was usedi na ll cyclic carbenec omplexes,o n the other nitrogen atom the cycloalkyl group was varied,i nvolving the cyclohexyl, cyclooctyl, cyclododecyl and cyclopentadecylg roup.…”

Section: Resultsmentioning

confidence: 99%

A Structure‐Based Activity Study of Highly Active Unsymmetrically Substituted NHC Gold(I) Catalysts

et al. 2017

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Following the modular template synthesis using isonitriles,n ew unsymmetrically substituted five-membered saturated N-heterocyclic carbene (NHC)a nd N-heterocyclic oxo-carbene (NHOC) gold(I) complexes were prepared. With these species and already reported complexes,adetailed study concerning the catalytic activities of the complex classes available by the isonitrile routew as conducted. Thec atalytic properties of twelve different types of NHOCs, saturated and unsaturated NHC gold(I) pre-catalysts with different substituents,a sw ella s one representative of as ix-membered NHC and one N-acyclic carbene (NAC)g old(I) complex were analyzed by utilizing the phenol synthesisa satest reaction. Fort his reaction, the saturated NHC gold(I) complexes achieved higher conversions than the corresponding unsaturated NHCs andt he NHOC systems.W hile unsaturated NHC complexes show higher catalytic activity during the initial phase of the conversion, due to ah igher stability,h igher turnover numbers( TONs) were obtained for the corresponding saturated systems.Acyclopentadecyls ubstituenta tn itrogen turned out to be the privileged substituent for all of the unsymmetrical complexes. Furthermore,w ed etectedt hat light exclusion can significantly increase the catalytic activity of NHC gold(I) complexes for phenols ynthesis.

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Section: Resultsmentioning

confidence: 99%

A Structure‐Based Activity Study of Highly Active Unsymmetrically Substituted NHC Gold(I) Catalysts

et al. 2017

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“…1 H NMR (CDCl 3, 500.16 MHz, 298 K): δ 7.42 (t, 2H, 3 J HH = 8 Hz, C 6 H 3 ), 7.23 (d, 4H, 3 J HH = 8 Hz, C 6 H 3 ), 4.05 (s, 4H, CH 2 ), 3.00 (sept, 4H, 3 J HH = 6.9 Hz, CH(CH 3 ) 2 ), 1.37 (d, 12H, 3 J HH = 6.9 Hz, CH(CH 3 ) 2 ), 1.33 (d, 12H, 3 J HH = 6.9 Hz, CH(CH 3 ) 2 ). 13 2 ] the K 13 CN was used). The reaction mixture was stirred for overnight at room temperature.…”

Section: ■ Experimental Sectionsmentioning

confidence: 99%

End-On and Side-On π-Acid Ligand Adducts of Gold(I): Carbonyl, Cyanide, Isocyanide, and Cyclooctyne Gold(I) Complexes Supported by N-Heterocyclic Carbenes and Phosphines

et al. 2012

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N-heterocyclic carbene ligand SIDipp (SIDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) and trimesitylphosphine ligand have been used in the synthesis of gold(I) cyanide, t-butylisocyanide, and cyclooctyne complexes (SIDipp)Au(CN) (3), (Mes(3)P)Au(CN) (4), [(Mes(3)P)(2)Au][Au(CN)(2)] (5), [(SIDipp)Au(CN(t)Bu)][SbF(6)] ([6][SbF(6)]), [(SIDipp)Au(cyclooctyne)][SbF(6)] ([8][SbF(6)]), and [(Mes(3)P)Au(cyclooctyne)][SbF(6)] ([9][SbF(6)]). A detailed computational study has been carried out on these and the related gold(I) carbonyl adducts [(SIDipp)Au(CO)][SbF(6)] ([1][SbF(6)]), [(Mes(3)P)Au(CO)][SbF(6)] ([2][SbF(6)]), and [(Mes(3)P)Au(CN(t)Bu)](+) ([7](+)). X-ray crystal structures of 3, 5, [6][SbF(6)], [8][SbF(6)], and [9][SbF(6)] revealed that they feature linear gold sites. Experimental and computational data show that the changes in π-acid ligand on (SIDipp)Au(+) from CO, CN(-), CN(t)Bu, cyclooctyne as in [1](+), 3, [6](+), and [8](+) did not lead to large changes in the Au-C(carbene) bond distances. A similar phenomenon was also observed in Au-P distance in complexes [2](+), 4, [7](+), and [9](+) bearing trimesitylphosphine. Computational data show that the Au-L bonds of "naked" [Au-L](+) or SIDipp and Mes(3)P supported [Au-L](+) (L = CO, CN(-), CN(t)Bu to cyclooctyne) have higher electrostatic character than covalent character. The Au←L σ-donation and Au→L π-back-donation contribute to the orbital term with the former being the dominant component, but the latter is not negligible. In the Au-CO adducts [1](+)and [2](+), the cationic gold center causes the polarization of the C-O σ and π orbitals toward the carbon end making the coefficients at the two atoms more equal which is mainly responsible for the large blue shift in the CO stretching frequency. The SIDipp and Mes(3)P supported gold(I) complexes of cyanide and isocyanide also exhibit a significant blue shift in υ(CN) compared to that of the free ligands. Calculated results for Au(CO)Cl and Au(CF(3))CO suggest that the experimentally observed blue shift in ν(CO) of these compounds may at least partly be caused by intermolecular forces.

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“…Bis(isocyanide)palladium(II) chlorides 7a and 8a were easily prepared in high yields by employing the reaction between Pd(CH 3 CN)Cl 2 and the corresponding isocyanide at room temperature. [20] We attempted the reaction of 1a (0.5 mmol) with 7a (0.5 mmol) under the hydrolysis reaction conditions, and to our surprise, the sp 2 /sp 3 -hybridized dual C-H functionalized product 9a was isolated instead of hydrolysis product 3a. The structure of 9a was further confirmed by X-ray analysis [Scheme 2, Equation (1) (3)] under the hydrolysis conditions.…”

Section: Resultsmentioning

confidence: 99%

Chemoselective Pd‐Catalyzed Isocyanide Insertion Reaction of Enaminones by C–H Functionalization: Hydrolysis or Cyclization through 1,3‐Palladium Migration

Wang

Cao

et al. 2015

Eur J Org Chem

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A chemoselective palladium-catalyzed isocyanide insertion reaction of enaminones was developed. Amide derivatives were synthesized by this C-H functionalization and subse-[a] Key 4699 quent hydrolysis reactions. 4-Aminoquinoline derivatives were prepared by this C-H functionalization, which includes a 1,3-palladium migration in the process.With the optimal conditions in hand, we explored the reactions of enaminones 1 with 2a (Table 2). For enaminones that have an unsubstituted or o-Me-substituted aryl www.eurjoc.org

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A Short Way to Switchable Carbenes

Abstract: A new, one-step route to N-heterocyclic oxo-carbene complexes (NHOCs), representatives of chemo-switchable NHC complexes, is reported. This simple procedure provides an easy access to gold, palladium and platinum complexes of these ligands.

Cited by 116 publications

References 32 publications

A Structure‐Based Activity Study of Highly Active Unsymmetrically Substituted NHC Gold(I) Catalysts

A Structure‐Based Activity Study of Highly Active Unsymmetrically Substituted NHC Gold(I) Catalysts

End-On and Side-On π-Acid Ligand Adducts of Gold(I): Carbonyl, Cyanide, Isocyanide, and Cyclooctyne Gold(I) Complexes Supported by N-Heterocyclic Carbenes and Phosphines

Chemoselective Pd‐Catalyzed Isocyanide Insertion Reaction of Enaminones by C–H Functionalization: Hydrolysis or Cyclization through 1,3‐Palladium Migration

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