- Au-catalyzed biaryl coupling to generate 5- to 9-membered rings: Turnover-limiting reductive elimination versus π-complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes-substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to π-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the π-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Corrie, Tom J. A.,Ball, Liam T.,Russell, Christopher A.,Lloyd-Jones, Guy C.
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supporting information
p. 245 - 254
(2017/05/29)
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- Au-Catalyzed Biaryl Coupling to Generate 5- To 9-Membered Rings: Turnover-Limiting Reductive Elimination versus ?-Complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes - substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to ?-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the ?-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Ball, Liam T.,Corrie, Tom J. A.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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supporting information
p. 245 - 254
(2021/09/04)
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- Efficient palladium-catalyzed C(sp2)-H activation towards the synthesis of fluorenes
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A facile protocol for the synthesis of fluorene derivatives has been developed through palladium-catalyzed cyclization of 2′-halo-diarylmethanes via activation of arylic C-H bonds. The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates to convert into their corresponding fluorenes in good to excellent yields. Studies revealed that this Pd-catalyzed cyclization was also available for the substrates of 2′-chloro-diarylmethanes and no catalyst poisoning occurred for 2′-iodo-diphenylmethane.
- Song, Juan,Li, Yali,Sun, Wei,Yi, Chenglong,Wu, Hao,Wang, Haotian,Ding, Keran,Xiao, Kang,Liu, Chao
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p. 9030 - 9033
(2016/11/11)
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- Highly efficient and versatile synthesis of polyarylfluorenes via Pd-catalyzed C-H bond activation
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A facile protocol for the Pd-catalyzed preparative synthesis of fluorene derivatives has been developed. While a wide range of fluorenes were easily obtained with high efficiency and selectivity under mild conditions, excellent functional group tolerance
- Hwang, Seung Jun,Kim, Hyun Jin,Chang, Sukbok
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supporting information; experimental part
p. 4588 - 4591
(2009/12/09)
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