Electrophilic alkynylation: the dark side of acetylene chemistry

Brand, Jonathan P.; Waser, Jérôme

doi:10.1039/c2cs35034c

Cited by 401 publications

(170 citation statements)

References 90 publications

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“…The reaction was faster with electron-deficient reagent 1c, however. Methylated TIPS-EBX reagents 1e and 1f led to the formation of the ethynylated product 3b in moderate yields and relatively short reaction times (entries [4][5]. Finally, we found that TIPS benziodioxole reagents 5 and 6 are also efficient alkynylation reagents under these conditions, although in this case the alkynylation reaction is slower (entries 6-7).…”

Section: Alkynylation Reactions With Modified Ethynyl Benziodoxolonesmentioning

confidence: 76%

“…The characterization data corresponded to the reported values. [4] 2-Iodosyl-5-nitrobenzoic acid and 2-iodosyl-3-nitrobenzoic acid (19,20) Following a reported procedure, [5] fuming nitric acid (3.3 mL) was added to 2-iodobenzoic acid (14) (5.0 g, 20 mmol, 1.0 equiv) in concentrated H2SO4 (6.7 mL). The reaction was equipped with a cooler and a nitrous vapor trap and was heated at 100 °C for 1 h. The reaction mixture was then poured onto ice-water and filtered.…”

Section: -[(Triiso-propylsilyl)ethynyl]-12-benziodoxol-3(1h)-one (1b)mentioning

confidence: 99%

“…The characterization data corresponded to the reported values. [2] Phenyl(trimethylsilylethynyl)iodonium triflate (4) Following the reported procedure, [4] phenyliodonium diacetate (18) (1.6 g, 5.0 mmol, 1.0 equiv) was diluted with CH2Cl2 (5 mL) in a two-neck flask and the mixture was stirred 5 min. Tf2O (0.42 mL, 2.5 mmol, 0.50 equiv) was added dropwise at 0 °C and the resulting yellow mixture was stirred 30 min.…”

Section: -[(Triiso-propylsilyl)ethynyl]-12-benziodoxol-3(1h)-one (1b)mentioning

confidence: 99%

“…In this case, the Umpolung of the reactivity of acetylenes is required. [4] A particularly interesting class of nucleophiles is constituted by α-disubstituted carbonyl compounds, as the addition of the triple bond in alpha position allows the formation of allcarbon quaternary centers, which cannot be accessed using the normal polarity of acetylenes. Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

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Ethynylbenziodoxolones (EBX) as Reagents for the Ethynylation of Stabilized Enolates

González¹,

Brand²,

Mondière³

et al. 2013

Adv Synth Catal

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106

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Abstract. Herein, we report a detailed study on the electrophilic alkynylation of cyclic keto-esters and amides with ethynylbenziodoxolone (EBX) reagents. The structure and stability of this class of reagents is first described more in details. DSC experiments showed a strong exothermic decomposition with EBX reagents, leading to guidelines for the safe use of these compounds. The extension of the method to aromatic alkynes and a broad range of benziodoxol(on)e reagents is then reported. Based on our preliminary results using cinchona-based phase-transfer catalysts, the enantioselective alkynylation of cyclic keto-esters could be achieved. Binaphthyl-derived ammonium catalysts developed by Maruoka and co-workers gave the highest asymmetric induction with up to 79% ee for an indanone-derived keto-ester.Throughout this work, asymmetric induction was observed only in the case of benziodoxolone reagents, demonstrating their superiority over conventional alkynyliodonium salts. The deeper understanding gained about the factors leading to higher asymmetric induction will be very useful in the future to develop a truly general and highly enantioselective alkynylation method.

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Section: Alkynylation Reactions With Modified Ethynyl Benziodoxolonesmentioning

confidence: 76%

Section: -[(Triiso-propylsilyl)ethynyl]-12-benziodoxol-3(1h)-one (1b)mentioning

confidence: 99%

Section: -[(Triiso-propylsilyl)ethynyl]-12-benziodoxol-3(1h)-one (1b)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ethynylbenziodoxolones (EBX) as Reagents for the Ethynylation of Stabilized Enolates

González¹,

Brand²,

Mondière³

et al. 2013

Adv Synth Catal

Self Cite

106

View full text Add to dashboard Cite

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“…In stark contrast, the addition of alkynes onto nucleophiles requires an inversion of their inherent reactivity (an Umpolung, Scheme 2.1, B). This approach is more challenging and has been consequently less developed [7][8][9]. When considering the omnipresence of nucleophiles not only in synthetic organic chemistry, but also in chemical biology and materials science, this is an important shortcoming.…”

Section: Introduction: the Umpolung Of Alkynesmentioning

confidence: 99%

Alkynylation with Hypervalent Iodine Reagents

Waser

2015

Topics in Current Chemistry

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Alkynes are among the most versatile functional groups in organic synthesis. They are also frequently used in chemical biology and materials science. Whereas alkynes are traditionally added as nucleophiles into organic molecules, hypervalent iodine reagents offer a unique opportunity for the development of electrophilic alkyne synthons. Since 1985, alkynyliodonium salts have been intensively used for the alkynylation of nucleophiles, in particular soft carbon nucleophiles and heteroatoms. They have made especially a strong impact in the synthesis of highly useful ynamides. Nevertheless, their use has been limited by their instability. Since 2009, more stable ethynylbenziodoxol(on)e (EBX) reagents have been discovered as superior electrophilic alkyne synthons in many transformations. They can be used for the alkynylation of acidic C-H bonds with bases or aromatic C-H bonds using transition metal catalysts. They were also highly successful for the functionalization of radicals or transition metal-catalyzed domino processes. Finally, they allowed the alkynylation of a further range of heteroatom nucleophiles, especially thiols, under exceptionally mild conditions. With these recent discoveries, hypervalent iodine reagents have definitively demonstrated their utility for the efficient synthesis of alkynes based on non-classical disconnections.

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Preparation of 5‐(Triisopropylalkynyl) Dibenzo[ b , d ]Thiophenium Triflate

Waldecker

2020

Organic Syntheses

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This article describes the procedure for preparation of 5‐(Triisopropylalkynyl) dibenzo[b,d]thiophenium triflate. It presents some of the important points to be considered, the conditions that need to be maintained, characterization data, and the reagents required, as well as the techniques used and the equipment setup that are vital to carrying out the process. Prior to performing each reaction, a thorough hazard analysis and risk assessment should be carried out with regard to each chemical substance and experimental operation on the scale planned and in the context of the laboratory where the procedures will be carried out. The article also describes the hazards associated with working with chemicals and the ways to deal with these hazards.

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Electrophilic alkynylation: the dark side of acetylene chemistry

Cited by 401 publications

References 90 publications

Ethynylbenziodoxolones (EBX) as Reagents for the Ethynylation of Stabilized Enolates

Ethynylbenziodoxolones (EBX) as Reagents for the Ethynylation of Stabilized Enolates

Alkynylation with Hypervalent Iodine Reagents

Preparation of 5‐(Triisopropylalkynyl) Dibenzo[ b , d ]Thiophenium Triflate

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