Gold catalysis in total synthesis – recent achievements

Pflästerer, Daniel; Hashmi, A. Stephen K.

doi:10.1039/c5cs00721f

Cited by 698 publications

(245 citation statements)

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“…Spectacular cationic cascades of polyolefins imitating Nature's squalene cyclases have been used in routes to terpenes and steroids and, more recently, elegant organocatalytic sequences have been marshalled to address problems in total synthesis [2,3]. The selective electrophilic activation of alkynes and allenes with gold complexes has seen a dramatic boom in recent times [4]. Combinations of anionic processes such as conjugate additions with alkylations or aldol reactions have also been used to great effect.…”

Section: Introductionmentioning

confidence: 99%

Some aspects of radical cascade and relay reactions

Quiclet‐Sire¹,

Zard²

2017

Proc. R. Soc. A.

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The ability to create carbon-carbon bonds is at the heart of organic synthesis. Radical processes are particularly apt at creating such bonds, especially in cascade or relay sequences where more than one bond is formed, allowing for a rapid assembly of complex structures. In the present brief overview, examples taken from the authors' laboratory will serve to illustrate the strategic impact of radical-based approaches on synthetic planning. Transformations involving nitrogen-centred radicals, electron transfer from metallic nickel and the reversible degenerative exchange of xanthates will be presented and discussed. The last method has proved to be a particularly powerful tool for the intermolecular creation of carbon-carbon bonds by radical additions even to unactivated alkenes. Various functional groups can be brought into the same molecule in a convergent manner and made to react together in order to further increase the structural complexity. One important benefit of this chemistry is the so-called RAFT/MADIX technology for the manufacture of block copolymers of almost any desired architecture.

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Section: Introductionmentioning

confidence: 99%

Some aspects of radical cascade and relay reactions

Quiclet‐Sire¹,

Zard²

2017

Proc. R. Soc. A.

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“…3 Catalysis by gold is emerging as a powerful synthetic tool. 4 We recently reported a gold-catalyzed intermolecular arylation of electron-rich arenes by aryltrimethylsilanes (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Au-Catalyzed Biaryl Coupling To Generate 5- to 9-Membered Rings: Turnover-Limiting Reductive Elimination versus π-Complexation

et al. 2016

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ABSTRACT:The intramolecular gold-catalyzed arylation of arenes by aryltrimethylsilanes has been investigated from both a mechanistic and preparative aspect. The reaction generates five to nine membered rings, and of the 44 examples studied, ten include a heteroatom (N, O). The tethering of the arene to the arylsilane not only provides 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 electronics of the arene and changes from reductive elimination to π-complexation for arenes bearing strongly electronwithdrawing substituents (σ >0.43). Reductive elimination is accelerated by electron-donating substituents ( = ̶ 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 results in faster reductive elimination from Ar-Au(X)-Ar, and to the π-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.

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“…Furthermore, occasionally reactions typically catalyzed by homogeneous catalysts have also been reported to be catalyzed by heterogeneous catalysts [24], and occasionally reaction typically catalyzed by heterogeneous catalysts have also been reported to be catalyzed by homogeneous gold(III) complexes [25]. Gold-based catalysts supported by metal oxides (such as TiO 2 , Fe 2 O 3 , Fe 3 O 4 , SiO 2 and Al 2 O 3 ) [26][27][28][29][30][31][32], carbon nanotube [33], polymer [34,35], graphene oxide [36], and gold complexes [37][38][39][40] are all good candidate for the hydrogenation of nitroarenes due to their high catalytic activities.…”

Section: Introductionmentioning

confidence: 97%