Evolution of Propargyl Ethers into Allylgold Cations in the Cyclization of Enynes

Jiménez‐Núñez, Eloísa; Raducan, Mihai; Lauterbach, Thorsten; Molawi, Kian; Solorio, César R.; Echavarren, Antonio M.

doi:10.1002/anie.200902248

Cited by 106 publications

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References 53 publications

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“…107 The reaction proceeds through intermediate 89 , which evolves by intramolecular attack of the OR at the electrophilic site of the cyclopropane to form 90 . α,β-Unsaturated gold( i ) carbene 91 , generated by cleavage of the oxonium bridge, then undergoes cyclopropanation with the pending alkene.…”

Section: Evolution Of the Key Gold Intermediatesmentioning

confidence: 99%

Intriguing mechanistic labyrinths in gold(i) catalysis

2014

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Section: Evolution Of the Key Gold Intermediatesmentioning

confidence: 99%

Intriguing mechanistic labyrinths in gold(i) catalysis

2014

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“…In order to predict the gold fragment structure [6,7b,9], theory can help by assessing reasonable predictions on metal configuration and structure. We present here a computational study for one of the interesting gold reactions in phenol synthesis catalyzed by [(biphenyl-NMe 2 )Ph 2 PAuCl] (A), which potentially exhibits weak olefin coordination to Au(I) that is relevant in experimental studies by the Hashmi and Echavarren groups [10a,b,11,12].…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of weak CC double bond coordination in a gold (I) catalyst precursor

Touil

Bechem

Hashmi

et al. 2010

Journal of Molecular Structure: THEOCHEM

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“…The reaction presumably proceeds via intermediates 43 and 44, followed by an intramolecular Prins reaction and metal loss to form 37 (Scheme 10) [72]. Identical stereocontrol was observed in the cyclization proceeding via 1,5-OR migration through intermediate 21 (Scheme 4) [73]. All …”

Section: Gold-catalyzed Cyclization Of Simple 16-enynesmentioning

confidence: 97%

“…17a-b substituted with alcohols, ethers, and silyl ethers at the propargylic position react with gold(I) catalysts by a new type of intramolecular 1,5-migration of OR groups (Scheme 3)[73]…”

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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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Evolution of Propargyl Ethers into Allylgold Cations in the Cyclization of Enynes

Cited by 106 publications

References 53 publications

Intriguing mechanistic labyrinths in gold(i) catalysis

Intriguing mechanistic labyrinths in gold(i) catalysis

Theoretical study of weak CC double bond coordination in a gold (I) catalyst precursor

Complexity via Gold-Catalyzed Molecular Gymnastics

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