Gold(I)—Phosphine Catalyst for the Highly Chemoselective Dehydrogenative Silylation of Alcohols.

Ito, Hajime; Takagi, K.; Miyahara, Takahiro; Sawamura, Masaya

doi:10.1002/chin.200544064

Cited by 4 publications

(6 citation statements)

References 4 publications

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“…Gold catalysts achieve the dehydrogenative silylation of alcohols. 241 Mechanistic studies by Ito et al 139 and later Le Floch et al, 240 both using Xantphos derived ligands, are consistent with gold(I) hydride intermediates. The proposed mechanism begins with a transmetalation between a silane and a gold(I) precursor [(Xantphos)Au] + [X] − to form a transient terminal (Xantphos)gold(I) hydride, which in the presence of more (Xantphos)gold(I) forms a hydride-bridged digold complex (Scheme 101; see also section 2.3.2 for the characterization of such species).…”

Section: Gold Hydrides In Catalytic Alcohol Silylationmentioning

confidence: 79%

“…139,240 Sawarmura et al first reported the dehydrogenative silylation of alcohols in good yield using (Xantphos)AuCl as a precatalyst (Scheme 82). 241 This system is highly selective for dehydrogenative silylation, tolerating functional groups such as alkenes, alkynes, ketones, aldehydes, alkyl halides, conjugated enones, esters, and carbamates. Further mechanistic studies revealed the intermediacy of a hydride-bridged digold cation.…”

Section: Silver Hydrides In Catalysismentioning

confidence: 99%

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Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity

2016

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Hydride complexes of copper, silver, and gold encompass a broad array of structures, and their distinctive reactivity has enabled dramatic recent advances in synthesis and catalysis. This Review summarizes the synthesis, characterization, and key stoichiometric reactions of isolable or observable coinage metal hydrides. It discusses catalytic processes in which coinage metal hydrides are known or probable intermediates, and presents mechanistic studies of selected catalytic reactions. The purpose of this Review is to convey how developments in coinage metal hydride chemistry have led to new organic transformations, and how developments in catalysis have in turn inspired the synthesis of reactive new complexes.

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Section: Gold Hydrides In Catalytic Alcohol Silylationmentioning

confidence: 79%

Section: Silver Hydrides In Catalysismentioning

confidence: 99%

Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity

2016

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“…It is important to point out that even though tris-coordinated gold complexes are well-known, their involvements in gold catalysis are rare. 54,55 While our efforts to extend this intermolecular trapping to carbonucleophiles have so far been unsuccessful, carboxylic acids were found to be suitable trapping reagents for the in situ generated R-oxo gold carbenes. As shown in Scheme 12A, 56 a serviceable 68% yield was obtained by using Mor-DalPhos as the metal ligand.…”

Section: Intermolecular Oxidation Of Terminal Alkynes Followed By Int...mentioning

confidence: 99%

A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

2014

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For the past dozen years, homogeneous gold catalysis has evolved from a little known topic in organic synthesis to a fully blown research field of significant importance to synthetic practitioners, due to its novel reactivities and reaction modes. Cationic gold(I) complexes are powerful soft Lewis acids that can activate alkynes and allenes toward efficient attack by nucleophiles, leading to the generation of alkenyl gold intermediates. Some of the most versatile aspects of gold catalysis involve the generation of gold carbene intermediates, which occurs through the approach of an electrophile to the distal end of the alkenyl gold moiety, and their diverse transformations thereafter. On the other hand, α-oxo metal carbene/carbenoids are highly versatile intermediates in organic synthesis and can undergo various synthetically challenging yet highly valuable transformations such as C–H insertion, ylide formation, and cyclopropanation reactions. Metal-catalyzed dediazotizations of diazo carbonyl compounds are the principle and most reliable strategy to access them. Unfortunately, the substrates contain a highly energetic diazo moiety and are potentially explosive. Moreover, chemists need to use energetic reagents to prepare them, putting further constrains on operational safety.In this Account, we show that the unique access to the gold carbene species in homogeneous gold catalysis offers an opportunity to generate α-oxo gold carbenes if both nucleophile and electrophile are oxygen. Hence, this approach would enable readily available and safer alkynes to replace hazardous α-diazo carbonyl compounds as precursors in the realm of gold carbene chemistry.For the past several years, we have demonstrated that alkynes can indeed effectively serve as precursors to versatile α-oxo gold carbenes. In our initial study, we showed that a tethered sulfoxide can be a suitable oxidant, which in some cases leads to the formation of α-oxo gold carbene intermediates. The intermolecular approach offers excellent synthetic flexibility because no tethering of the oxidant is required, and its reduced form is not tangled with the product. We were the first research group to develop this strategy, through the use of pyridine/quinolone N-oxides as the external oxidants. In this manner, we can effectively make a C–C triple bond a surrogate of an α-diazo carbonyl moiety in various gold catalyses. With terminal alkynes, we demonstrated that we can efficiently trap exclusively formed terminal carbene centers by internal nucleophiles en route to the formation of cyclic products, including strained oxetan-3-ones and azetidin-3-ones, and by external nucleophiles when a P,N-bidentate ligand is coordinated to gold. With internal alkynes, we generated synthetically useful regioselectivities in the generation of the α-oxo gold carbene moiety, which enables expedient formation of versatile enone products. Other research groups have also applied this strategy en route to versatile synthetic methods. The α-oxo gold carbenes appear to be more electrophilic...

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“…Thus, an alternative to its preparation is the catalytic dehydrogenative etherification of silanes with alcohols, analogous to the formation of silanols, in which the only byproduct is molecular hydrogen (see Scheme 25). Several homogeneous catalysts have been used in this reaction based on different metals such as Au, 332 Rh, 333 Pt, 334 or Zn. 335 Since then, supported metal NPs have also been used as efficient catalyst for this reaction, whose main advantage is that in most of the cases they can be easily recycled from the reaction medium.…”

Section: Silane Oxidationmentioning

confidence: 99%

σ-H–H, σ-C–H, and σ-Si–H Bond Activation Catalyzed by Metal Nanoparticles

et al. 2019

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Activation of H-H, Si-H and C-H bonds through σ-bond coordination has grown in the past 30 years from a scientific curiosity to an important tool in the functionalization of hydrocarbons. Several mechanisms were discovered via which the initially σ-bonded substrate could be converted: oxidative addition, heterolytic cleavage, σ-bond metathesis, electrophilic attack, etc. The use of metal nanoparticles (NPs) in this area is a more recent development, but obviously nanoparticles offer a much richer basis than classical homogeneous and heterogeneous catalysts for tuning reactivity for such a demanding process as C-H functionalization. Here, we will review the surface chemistry of

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Gold(I)—Phosphine Catalyst for the Highly Chemoselective Dehydrogenative Silylation of Alcohols.

Cited by 4 publications

References 4 publications

Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity

Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity

A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

σ-H–H, σ-C–H, and σ-Si–H Bond Activation Catalyzed by Metal Nanoparticles

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