Elementary Steps of Gold Catalysis: NMR Spectroscopy Reveals the Highly Cationic Character of a “Gold Carbenoid”

Seidel, Günter; Mynott, Richard; Fürstner, Alois

doi:10.1002/anie.200806059

Cited by 270 publications

(92 citation statements)

References 80 publications

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“…9d The highly electrophilic nature of the α-oxo gold carbene moiety, especially for those without additional substitutions at the carbene center, can be understood by invoking the relatively weak back donation by the electronegative gold. 14 As a result, it is highly challenging to trapping these highly electrophilic gold carbenes with stoichiometric external nucleophiles.…”

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confidence: 99%

Tempering the Reactivities of Postulated α-Oxo Gold Carbenes Using Bidentate Ligands: Implication of Tricoordinated Gold Intermediates and the Development of an Expedient Bimolecular Assembly of 2,4-Disubstituted Oxazoles

Luo

et al. 2012

J. Am. Chem. Soc.

205

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2,4-Oxazole is an important structural motif in various natural products. An efficient modular synthesis of this structure is achieved via a [3+2] annulation between a terminal alkyne and a carboxamide by using a gold-catalyzed oxidation strategy. The postulated reactive intermediate, a terminal α-oxo gold carbene, previously known to be highly electrophilic and hence impropable to be trapped by stoichiometric external nucleophiles, is coerced to react smoothly with a carboxamide en route to the oxazole ring by a P,N- or P,S-bidentate ligand such as Mor-DalPhos; in stark contrast, often used ligands including monodentate phosphines and NHCs are totally ineffective. The role of these bidentate phosphines in this reaction is attributed to the formation of a tricoordinated gold carbene intermediate, which is less electrophilic and hence more chemoselective when reacting with nucleophiles. The success in using bidentate phosphine ligands to temper the reactivities of in-situ generated gold carbenes would likely open many new opportunities to apply the oxidative gold catalysis to the development of novel methods, and the implication of tricoordinated gold intermediates in homogeneous gold catalysis should stimulate further advance in gold catalysis.

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mentioning

confidence: 99%

Tempering the Reactivities of Postulated α-Oxo Gold Carbenes Using Bidentate Ligands: Implication of Tricoordinated Gold Intermediates and the Development of an Expedient Bimolecular Assembly of 2,4-Disubstituted Oxazoles

Luo

et al. 2012

J. Am. Chem. Soc.

205

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“…168,169 In parallel with the gold-catalyzed addition of cyclopropenes with alcohols reported by Lee and co-workers (Scheme 29), 108 Shi and Zhu have also reported one of the first examples of gold-catalyzed reactions of cyclopropene in 2008. 100 The cycloisomerization of arylvinylcyclopropene 83 catalyzed by gold(I) affords 2-vinyl-1H-indene derivatives 228 in good yields.…”

Section: Cyclopropenone Involved Cycloadditionmentioning

confidence: 85%

Recent developments of cyclopropene chemistry

2011

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This critical review discusses recent developments in the field of cyclopropene chemistry. Although several excellent reviews that mainly focused on the thermolysis and pyrolysis as well as metal-mediated reactions of cyclopropenes have been published, significant new developments have also been achieved in recent years. This brand new review provides an overview of the progress from 2007 to 2011 on the syntheses and transformations of cyclopropenes as well as their related mechanistic studies (238 references).

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“…Experimental support for the involvement of 6 has been obtained in reactions in which these intermediates have been trapped with alkenes [55], indoles, allyl silanes [56][57][58], and carbonyl compounds [59,60]. Proton loss from 6 can form 1,4-dienes in InCl 3 -catalyzed reactions of substrate in which R 0 is an alkyl group [27].The dual character of intermediates 5 as metal carbenes and carbocationic species has been recently discussed [1][2][3][4][61][62][63]. Conventionally, these complexes are often depicted as cyclopropyl gold carbenes 5, although DFT calculations show that these species have highly distorted structures, intermediate between cyclopropyl gold carbenes and gold-stabilized homoallylic carbocations [38,52].…”

mentioning

confidence: 99%

“…The dual character of intermediates 5 as metal carbenes and carbocationic species has been recently discussed [1][2][3][4][61][62][63]. Conventionally, these complexes are often depicted as cyclopropyl gold carbenes 5, although DFT calculations show that these species have highly distorted structures, intermediate between cyclopropyl gold carbenes and gold-stabilized homoallylic carbocations [38,52].…”

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confidence: 99%

Complexity via Gold-Catalyzed Molecular Gymnastics

Echavarren

Jiménez‐Núñez

2010

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Reactions of 1,6-enynes catalyzed by gold(I) complexes usually proceed stereospecifically through highly distorted cyclopropyl gold carbenes. Substrates with an alkoxy substituent at the propargylic position undergo stereoselective transformations through intermediates in which the OR group and the gold carbene are anti-oriented. Intramolecular attack of carbonyl groups to the cyclopropyl gold carbene is faster than the 1,5-migration of the OR groups, which itself is faster than the intramolecular cyclopropanation by a pendant alkenyl group. The intramolecular attack of carbonyl groups is the key transformation in the [2?2?2] gold-catalyzed cycloaddition, which has been applied in the total synthesis of (?)-orientalol F.Electrophilic metals catalyze the cyclization of 1,n-enynes to give a variety of cyclic structures (recent reviews in [1-4]) [5][6][7][8][9][10][11][12][13][14][15][16]. In the absence of nucleophiles, simple 1,6-enynes 1 undergo skeletal rearrangement to give products 2 (single exo-cleavage) and 3 (double exo-cleavage) ( Fig. 1) . In a third type skeletal rearrangement, dienes 4 (single endo-cleavage) were found using cationic Au(I) catalysts [5,38]. Products of type 4 were later found in reactions catalyzed by InCl 3 [27, 28], Fe(III) [6], or Ru(II) [39]. Cyclobutenes resulting from a [2?2] cycloaddition process have also been obtained from 1,6-[40], 1,7-[25, 29-31, 34, 41], and 1,8-enynes [42, 43]. Other type of cyclobutenes have been obtained in the palladium-[17, 18], platinum-[44], and gold-catalyzed cyclization of enynes [15,16,[45][46][47].Although dienes 2 obtained by the single exo-cleavage are identical to those formed by the metal-catalyzed metathesis of enynes [48,49], the mechanism of the skeletal rearrangement is very different [50,51]. For Au(I), the rearrangement was proposed to proceed via intermediates 5 (Fig. 2) [52]. On the other hand, the double-cleavage skeletal rearrangement usually leads to dienes 3 with predominant [1-4, 17-21, 38], or exclusive Z [53, 54] configuration. For Au(I), products of type 3 are obtained via rearranged carbene 6, followed by 1,2-H shift and protodemetalation [52]. Experimental support for the involvement of 6 has been obtained in reactions in which these intermediates have been trapped with alkenes [55], indoles, allyl silanes [56][57][58], and carbonyl compounds [59,60]. Proton loss from 6 can form 1,4-dienes in InCl 3 -catalyzed reactions of substrate in which R 0 is an alkyl group [27].The dual character of intermediates 5 as metal carbenes and carbocationic species has been recently discussed [1][2][3][4][61][62][63]. Conventionally, these complexes are often depicted as cyclopropyl gold carbenes 5, although DFT calculations show that these species have highly distorted structures, intermediate between cyclopropyl gold carbenes and gold-stabilized homoallylic carbocations [38,52]. A gold carbene has been formed in the gas phase, see [64,65]. Intermediates of type 5 are involved in other processes such as nucleophilic additions of heteronucleo...

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Elementary Steps of Gold Catalysis: NMR Spectroscopy Reveals the Highly Cationic Character of a “Gold Carbenoid”

Cited by 270 publications

References 80 publications

Tempering the Reactivities of Postulated α-Oxo Gold Carbenes Using Bidentate Ligands: Implication of Tricoordinated Gold Intermediates and the Development of an Expedient Bimolecular Assembly of 2,4-Disubstituted Oxazoles

Tempering the Reactivities of Postulated α-Oxo Gold Carbenes Using Bidentate Ligands: Implication of Tricoordinated Gold Intermediates and the Development of an Expedient Bimolecular Assembly of 2,4-Disubstituted Oxazoles

Recent developments of cyclopropene chemistry

Complexity via Gold-Catalyzed Molecular Gymnastics

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