Transition‐Metal‐Free Synthesis of Aryl‐Substituted <i>tert</i>‐Butyl Ynol Ethers through Addition/Elimination Substitution at an sp Centre

Gray, Vincent James; Slater, Ben; Wilden, Jonathan D.

doi:10.1002/chem.201203015

Cited by 21 publications

(16 citation statements)

References 52 publications

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“…This is in sharp contrast to our other work 24 where less coordinating cations lead to cis anions where the elimination is much slower and consequently the anion can be trapped prior to elimination. The 1,3-addition-elimination reaction of nucleophiles with alkynyl sulfonyl compounds has been well documented for both carbon nucleophiles (Truce, Ruano) 25,26 and heteroatoms (our previous work) 24 however it is interesting to see that the propensity for this reaction with alkynes is much lower than for other carbon nucleophiles as these have not been reported either by Ruano or Truce's original paper where sulfones have been employed. As a final note, it is clear that we have only presented diethyl sulfonamides as reactive partners in this study.…”

Section: Scheme 5 Potential Exchange Reactionscontrasting

confidence: 54%

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

et al. 2017

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a Alkynyl sulfonamides undergo sequential 1,4-then 1,2-addition/rearrangement with lithium acetylides to yield enediynes in the absence of any promoters or catalysts. Mechanistic investigations suggest that the reaction proceeds via 1,4-conjugate addition of the nucleophile to the unsaturated system to give a key alkenyl lithium species which is stabilised by an intramolecular coordination effect by a sulfonamide oxygen atom. This species can be considered a vinylidene carbenoid given the carbon atom bears both an anion (as a vinyllithium) and a leaving group (the sulfonamide). The intramolecular coordination effect serves to stabilise the vinyllithium but activates the sulfonamide motif towards nucleophilic attack by a second mole of acetylide. The resulting species can then undergo rearrangement to yield the enediyne framework in a single operation with concomitant loss of aminosulfinate.

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Section: Scheme 5 Potential Exchange Reactionscontrasting

confidence: 54%

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

et al. 2017

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“…The synthesis of tert ‐butoxyacetylenes was also reported by Wilden, who treated t BuOK with ethynyl sulfonamides in DMF (Scheme ) 71. Mixtures similar to those produced from sulfonylacetylenes were obtained, and complete selectivity in favor of the exclusive formation of ynol ethers was achieved in the absence of water.…”

Section: Sulfonyl Acetylenes As Alkynylating Reagentsmentioning

confidence: 58%

“…The addition of the alkoxide would afford both the ( Z )‐ and ( E )‐vinyl carbanions (disfavored for alkylacetylenes, which did not react), with the former easily evolving into ynol ethers by trans elimination, and the latter into olefins by protonation. Equilibration between the two carbanions would explain the complete selectivity observed under the optimal conditions 71…”

Section: Sulfonyl Acetylenes As Alkynylating Reagentsmentioning

confidence: 99%

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands, meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane

Tanase

Otaki

Nishida

et al. 2014

Chemistry A European J

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A series of tetragold(I) complexes supported by tetraphosphine ligands, meso- and rac-bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso- and rac-dpmppm) were synthesized and characterized to show that the tetranuclear Au(I) alignment varies depending on syn- and anti-arrangements of the two dpmppm ligands with respect to the metal chain. The structures of syn-[Au4 (meso-dpmppm)2X]X'3 (X = Cl; X' = Cl (4 a), PF6 (4 b), BF4 (4 c)) and syn-[Au4 (meso-dpmppm)2]X4 (X = PF6 (4 d), BF4 (4 e), TfO (4 f); TfO = triflate) involved a bent tetragold(I) core with a counter anion X incorporated into the bent pocket. Complexes anti-[Au4 (meso-dpmppm)2]X4 (X = PF6 (5 d), BF4 (5 e), TfO (5 f)) contain a linearly ordered Au4 string and complexes syn-[Au4 (rac-dpmppm)2X2]X'2 (X = Cl, X' = Cl (6 a), PF6 (6 b), BF4 (6 c)) and syn-[Au4 (rac-dpmppm)2]X4 (X = PF6 (6 d), BF4 (6 e), TfO (6 f)) consist of a zigzag tetragold(I) chain supported by the two syn-arranged rac-dpmppm ligands. Complexes 4 d-f, 5 d-f, and 6 d-f with non-coordinative large anions are strongly luminescent in the solid state (λmax = 475-515 nm, Φ = 0.67-0.85) and in acetonitrile (λmax = 491-520 nm, Φ = 0.33-0.97); the emission was assigned to phosphorescence from (3) [dσ*σ*σ* pσσσ] excited state of the Au4 centers on the basis of DFT calculations as well as the long lifetime (a few μs). The emission energy is predominantly determined by the HOMO and LUMO characters of the Au4 centers, which depend on the bent (4), linear (5), and zigzag (6) alignments. The strong emissions in acetonitrile were quenched by chloride anions through simultaneous dynamic and static quenching processes, in which static binding of chloride ions to the Au4 excited species should be the most effective. The present study demonstrates that the structures of linear tetranuclear gold(I) chains can be modified by utilizing the stereoisomeric tetraphosphines, meso- and rac-dpmppm, which may lead to fine tuning of the strongly luminescent properties intrinsic to the Au(I) 4 cluster centers.

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“…In an attempt to develop milder conditions for preparing alkynyl ethers, 38 we reasoned that elimination reactions of enol triflates derived from α-alkoxy ketones might be performed with weaker, non-nucleophilic bases. Following the procedure of Muthusamy et al, 21 α-alkoxy ketones were prepared in a single step from α-diazo ketones and alcohols in the presence of catalytic quantities of indium triflate (Scheme 7).…”

Section: [33]-sigmatropic Rearrangement Of Allylmentioning

confidence: 99%

Tandem Bond-Forming Reactions of 1-Alkynyl Ethers

Minehan

2016

Acc. Chem. Res.

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Electron-rich alkynes, such as ynamines, ynamides, and ynol ethers, are functional groups that possess significant potential in organic chemistry for the formation of carbon-carbon bonds. While the synthetic utility of ynamides has recently been expanded considerably, 1-alkynyl ethers, which possess many of the reactivity features of ynamides, have traditionally been far less investigated because of concerns about their stability. Like ynamides, ynol ethers are relatively unhindered to approach by functional groups present in the same or different molecules because of their linear geometry, and they can potentially form up to four new bonds in a single transformation. Ynol ethers also possess unique reactivity features that make them complementary to ynamides. Research over the past decade has shown that ynol ethers formed in situ from stable precursors engage in a variety of useful carbon-carbon bond-forming processes. Upon formation at -78 °C, allyl alkynyl ethers undergo a rapid [3,3]-sigmatropic rearrangement to form allyl ketene intermediates, which may be trapped with alcohol or amine nucleophiles to form γ,δ-unsaturated carboxylic acid derivatives. The process is stereospecific, takes place in minutes at cryogenic temperatures, and affords products containing (quaternary) stereogenic carbon atoms. Trapping of the intermediate allyl ketene with carbonyl compounds, epoxides, or oxetanes instead leads to complex α-functionalized β-, γ-, or δ-lactones, respectively. [3,3]-Sigmatropic rearrangement of benzyl alkynyl ethers also takes place at temperatures ranging from -78 to 60 °C to afford substituted 2-indanones via intramolecular carbocyclization of the ketene intermediate. tert-Butyl alkynyl ethers containing pendant di- and trisubstituted alkenes and enol ethers are stable to chromatographic isolation and undergo a retro-ene/[2 + 2] cycloaddition reaction upon mild thermolysis (90 °C) to afford cis-fused cyclobutanones and donor-acceptor cyclobutanones in good to excellent yields and diastereoselectivities. This process, which takes place under neutral conditions and proceeds through an aldoketene intermediate, obviates the need to employ moisture-sensitive and/or unstable acid chlorides under basic conditions for intramolecular [2 + 2] cycloaddition reactions. Furthermore, Lewis acid-catalyzed intramolecular condensations of both ethyl and tert-butyl ynol ethers with tethered acetals efficiently provide protected five-, six-, and seven-membered cyclic Baylis-Hilman adducts. Metalated ethoxyacetylene can also participate in multiple bond-forming reactions that avoid isolation of the alkynyl ether intermediate. Lewis acid-promoted tandem additions employing epoxides/oxetanes and carbonyl compounds give rise to (Z)-α-alkylidene and α-benzylidene lactones stereoselectively in high overall yields. Three new carbon-carbon bonds and a ring are formed in this atom-economical single-flask transformation, resulting in a significant increase in molecular complexity. This Account provides a detailed overview of these...

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Transition‐Metal‐Free Synthesis of Aryl‐Substituted tert‐Butyl Ynol Ethers through Addition/Elimination Substitution at an sp Centre

Cited by 21 publications

References 52 publications

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands, meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane

Tandem Bond-Forming Reactions of 1-Alkynyl Ethers

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