2011
DOI: 10.1002/cjoc.201180398
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Mechanism of Gold(I)‐Catalyzed Conia‐ene Reaction of β‐Ketoesters with Alkynes: A DFT Study

Abstract: Density functional calculations have been performed to comparatively investigate two possible pathways of Au(I)-catalyzed Conia-ene reaction of β-ketoesters with alkynes. Our studies find that, under the assistance of trifluoromethanesulfonate (TfO), the β-ketoester is the most likely to undergo Model II to isomerize into its enol form, in which TfO plays a proton transfer role through a 6-membered ring transition state. The coordination of the Au(I) catalyst to the alkynes triple bond can enhance the eletroph… Show more

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Cited by 4 publications
(4 citation statements)
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“…The methodology provided access to both monocyclic and bicyclic exo -methylenecyclopentanes and cyclohexanes in good yields and diastereoselectivities, Scheme . Mechanistically, the reaction involved nucleophilic attack of the enol form of the ketoesters to the initially generated gold­(I) alkyne complex. , This reaction, however, has been limited to terminal alkynes as carbocyclization onto nonterminal alkyne variants was unsuccessful probably due to a 1,3-allylic strain in the transition state 6 that leads to the 5- exo - dig cyclization products 7 . Correspondingly, utilization of β-ketoesters with appended nonterminal α-3′-alkynyl derivatives 8 essentially eliminates the allylic strain in the transition state 9 , promoting the Au­(I)-mediated 5- endo - dig cyclization of dicarbonyl compounds onto the appended nonterminal alkynyl moieties, giving the cyclopentene products 10 , Scheme .…”
Section: Introductionmentioning
confidence: 99%
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“…The methodology provided access to both monocyclic and bicyclic exo -methylenecyclopentanes and cyclohexanes in good yields and diastereoselectivities, Scheme . Mechanistically, the reaction involved nucleophilic attack of the enol form of the ketoesters to the initially generated gold­(I) alkyne complex. , This reaction, however, has been limited to terminal alkynes as carbocyclization onto nonterminal alkyne variants was unsuccessful probably due to a 1,3-allylic strain in the transition state 6 that leads to the 5- exo - dig cyclization products 7 . Correspondingly, utilization of β-ketoesters with appended nonterminal α-3′-alkynyl derivatives 8 essentially eliminates the allylic strain in the transition state 9 , promoting the Au­(I)-mediated 5- endo - dig cyclization of dicarbonyl compounds onto the appended nonterminal alkynyl moieties, giving the cyclopentene products 10 , Scheme .…”
Section: Introductionmentioning
confidence: 99%
“…Several notable strategies for construction of seven-membered ring compounds are also discussed. Several reviews have been published on Au-catalyzed transformations focusing on cyclization reactions detailing the nature of reactivity, ligand effects, substrate class-dependent reactivities and synthetic utilities, ,, and mechanistic considerations. ,, This review focuses on presenting methodologies for the preparation of MSRs organized by concisely detailing aspects of the ring-closure pathway through either stepwise or direct cyclization. Examples of Au-mediated cascade reactions of different substrate classes including indoles and related heterocycles, alkynols, allene–enones, enyne–ethers, and alkynyl ketone derivatives undergoing sequential or stepwise medium-sized ring formation through rearrangements, tandem processes, or ring expansions are given.…”
Section: Introductionmentioning
confidence: 99%
“…To shed more light on the nature of gold‐catalyzed Conia‐ene cyclization, especially of substrates bearing internal alkynes, the reaction was investigated computationally. To the best of our knowledge, there is only one previous report of a DFT study of the discussed reaction . In this account, 5 ‐ exo‐dig cyclization of terminal alkynes was investigated.…”
Section: Resultsmentioning
confidence: 99%
“…This contrasts with experimental data that supports the widely accepted mechanism proceeding via anti addition. Moreover, in the discussed report, the calculations were performed on the E ‐enol form of the β‐ketoester, whereas the Z form is considerably more stable owing to stabilization by an internal hydrogen bond, which was left without comment…”
Section: Resultsmentioning
confidence: 99%