Effective transformation of unactivated alkynes into ketones or acetals with a gold(III) catalyst

Fukuda, Yukitoshi; Utimoto, Kiitirô

doi:10.1021/jo00011a058

Cited by 458 publications

(216 citation statements)

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“…1,2 Classical Kucherov procedures for alkynes' hydration into ketones employ mercuric salt as the catalyst in aqueous sulfuric acid. 3,4 Due to the toxicity of Hg salts, many other metal-catalyzed alkyne hydration procedures have been developed, including ones catalyzed by Ru, 5 Rh, 6 Pd, 7 Pt, 8,9 Sn−W, 10 Au, [11][12][13][14][15][16][17]18,19 Ir,20,21 Co, 22 Ag, 23,24 etc. Besides various metal catalysts, Brønsted-acidcatalyzed hydration reactions also exist in the literature.…”

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confidence: 99%

Metal-Free Markovnikov-Type Alkyne Hydration under Mild Conditions

2016

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A Markovnikov-type alkyne hydration protocol is presented using 20% CF 3 SO 3 H (TfOH) as the catalyst under unprecedented mild conditions applicable to various alkynes, including terminal arylalkynes, terminal nonfunctionalized aliphatic alkynes, and internal alkynes with excellent regioselectivity in good to excellent yields (average yields >85%). The reaction procedure operates under mild conditions (25−70°C), with broad functional group compatibility, and uses only slightly more than a stoichiometric amount of water in the absence of any transition metal. The success of this protocol hinges upon the utilization of trifluoroethanol as the solvent.C onverting alkynes into carbonyl compounds through hydration, especially Markovnikov-type hydration (Scheme 1a), is a fundamental transformation in organic synthesis with 100% atom economy. 1,2 Classical Kucherov procedures for alkynes' hydration into ketones employ mercuric salt as the catalyst in aqueous sulfuric acid. 3,4 Due to the toxicity of Hg salts, many other metal-catalyzed alkyne hydration procedures have been developed, including ones catalyzed by Ru, 5 Rh, 6 Pd, 7 Pt, 8,9 Sn−W, 10 Au, [11][12][13][14][15][16][17]18,19 Ir,20,21 Co, 22 Ag, 23,24 etc. Besides various metal catalysts, Brønsted-acidcatalyzed hydration reactions also exist in the literature. 25,26 However, most of the reactions reported so far have suffered from at least one drawback: (1) high temperature (>100°C); (2) expensive noble metals (Ru, Rh, Pd, Pt, Au, Ir, Ag, etc.); (3) narrow functional group compatibility; (4) large excess of water and acidic additive besides the metal catalysts if any (Scheme 1b). Therefore, a method that could operate under mild conditions (i.e., room temperature) with broad functional group tolerance at the cost of close to a stoichiometric amount of water and a catalytic amount of acid in the absence of any transitional metal 27 would be highly desirable. In this paper, we describe such a protocol that fulfills all of these requirements (Scheme 1c).Our work was inspired by the facts that (1) vinyl (phenyl) carbocation can be strongly stabilized in CF 3 CH 2 OH (TFE) as the solvent and (2) TFE cannot react with the carbocation due to its low nucleophilicity. 28−30 Given that alkyne's hydration is generally via a vinyl carbocation intermediate, 31−34 we hypothesized that TFE's ability to stabilize a vinyl carbocation could decrease the transition state energy to form the carbocation intermediate, which may cause the hydration reaction to proceed under conditions milder than those of reactions occurring in other solvents. Besides, low Lewis basicity of TFE would not compete with the triple bond to be activated by the acid catalysts (including metal and Brønsted catalysts). To quantitatively compare the difference between TFE and other solvents, we conducted DFT calculation on the protonation step in different solvents (Figure 1). TFE and ethanol were selected as the solvents to conduct the DFT analysis comparison because these two solvents bear nearl...

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Metal-Free Markovnikov-Type Alkyne Hydration under Mild Conditions

2016

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“…When using a buffered system like mercury(II) triflate-TMU complex [3] a good functional group compatibility is observed, except for substrates containing acetal or benzyl groups. [4] Other methods have been reported that use catalysts based on gold(I), [5] gold(III), [6] platinum(II), [7] palladium(II), [8] rhodium (III) [9] and ruthenium(II) [10] to form the antiMarkovnikov product. These are very efficient catalyst but the main disadvantage of these methods is the cost of the catalysts based on noble metals.…”

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confidence: 99%

Versatile Methodology to Hydrate Alkynes, in the Presence of a Wide Variety of Functional Groups, with Mercury(II) p-Toluensulfonamidate, Under Catalytic, Mild, and Neutral Conditions

Corominas

Montaña

2013

Synthetic Communications

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“…1), which is known for more than fifteen years now, [17,18] and is part of the standard toolkit of organic synthesis [19][20][21][22] which makes it appealing for consideration in a theoretical study (see computational section). Firstly, the high yield under mild conditions indicates a clear thermodynamical preference for the products which enables a discussion solely on the basis of the energy differences on the potential energy hypersurface.…”

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Homogeneous Gold Catalysis: Mechanism and Relativistic Effects of the Addition of Water to Propyne

et al. 2010

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Homogeneous catalysis employing gold compounds is a rapidly developing field. Au(III) catalysts in particular are interesting, since they exhibit catalytic properties unseen in other metals. In this study we report for the first time the complete mechanism of the nucleophilic addition of water to triple bonds that have not specifically been activated. The effect that the coordination of solvent molecules has on the course of the catalytic cycle is demonstrated, and the importance of hydrogen bonds to guide the substrate through the mechanism is highlighted. The influence of relativistic effects, which are particularly important for very heavy metals such as gold, is investigated, and it is concluded that the catalytic activity of gold could be seen as a relativistic effect.

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Effective transformation of unactivated alkynes into ketones or acetals with a gold(III) catalyst

Cited by 458 publications

References 1 publication

Metal-Free Markovnikov-Type Alkyne Hydration under Mild Conditions

Metal-Free Markovnikov-Type Alkyne Hydration under Mild Conditions

Versatile Methodology to Hydrate Alkynes, in the Presence of a Wide Variety of Functional Groups, with Mercury(II) p-Toluensulfonamidate, Under Catalytic, Mild, and Neutral Conditions

Homogeneous Gold Catalysis: Mechanism and Relativistic Effects of the Addition of Water to Propyne

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