Unveiling the uncatalyzed reaction of alkynes with 1,2-dipoles for the room temperature synthesis of cyclobutenes

Alcaide, Benito; Almendros, Pedro; Fernández, Israel; Lázaro‐Milla, Carlos

doi:10.1039/c4cc10111a

Cited by 39 publications

(20 citation statements)

References 19 publications

(17 reference statements)

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“…Sterically less‐hindered alkynyldiphenylphoshines were also converted into the desired products ( 5 l – 5 o ), with aryl, alkyl, and trialkylsilyl substituents on the C(sp) atom. Notably, in these cases, the [2+2] cycloaddition products were not formed ,. In contrast, in‐situ‐generated compound 4 did not form any adducts during the reactions with some sulfides.…”

Section: Resultssupporting

confidence: 89%

Synthesis and Characterization of Stable Phosphorus Carbabetaines

Yanai

Almendros

Takahashi

et al. 2018

Chemistry An Asian Journal

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Phosphorus 1,3- and 1,4-carbabetaines with 'P(+)-C-C(-)' and 'P(+)-C-C-C(-)' structures, respectively, in which the carbanion moiety was significantly stabilized by two trifluoromethylsulfonyl groups, have been synthesized and characterized. Analysis of their X-ray crystal structures revealed that any attractive interactions between the anionic and cationic moieties were negligibly weak. This result was corroborated by using natural bond orbital (NBO) and Bader's quantum theory of atoms in molecules (QTAIM) models. In contrast, performing the same analysis of a known 1,3-carbabetaine equivalent, which can be drawn as a 'P(+)-C-C=C-O(-)' resonance structure, revealed pronounced charge-transfer interactions between the anionic and cationic moieties.

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Section: Resultssupporting

confidence: 89%

Synthesis and Characterization of Stable Phosphorus Carbabetaines

Yanai

Almendros

Takahashi

et al. 2018

Chemistry An Asian Journal

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“… 15 , 16 The reaction of propiolates and other alkynes bearing electron-withdrawing groups with alkenes in the presence of Lewis 17 or Brønsted 18 acids also leads to cyclobutenes. 19 Interestingly, in the presence of gold(I), this type of alkyne reacts with alkenes to form 1,3-dienes 5 or lactones 6 ( Scheme 1 ). 20 …”

Section: Introductionmentioning

confidence: 99%

Cyclobutene vs 1,3-Diene Formation in the Gold-Catalyzed Reaction of Alkynes with Alkenes: The Complete Mechanistic Picture

et al. 2017

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The intermolecular gold(I)-catalyzed reaction between arylalkynes and alkenes leads to cyclobutenes by a [2 + 2] cycloaddition, which takes place stepwise, first by formation of cyclopropyl gold(I) carbenes, followed by a ring expansion. However, 1,3-butadienes are also formed in the case of ortho-substituted arylalkynes by a metathesis-type process. The corresponding reaction of alkenes with aryl-1,3-butadiynes, ethynylogous to arylalkynes, leads exclusively to cyclobutenes. A comprehensive mechanism for the gold(I)-catalyzed reaction of alkynes with alkenes is proposed on the basis of density functional theory calculations, which shows that the two pathways leading to cyclobutenes or dienes are very close in energy. The key intermediates are cyclopropyl gold(I) carbenes, which have been independently generated by retro-Buchner reaction from stereodefined 1a,7b-dihydro-1H-cyclopropa[a]naphthalenes.

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“…We have recently communicated the cyclization reaction of alkynes and Tf2C=CH2 to afford 1-aryl-2-alkyl-4,4-bis(triflyl)cyclobutenes, but this method was restricted so far to 1-aryl-2alkyl(aryl)substituted alkynes. [3] Due to the marked influence on the physical, chemical, and biological properties of small molecules imparted by the presence of heteroatoms, we envisaged the development of a mild method for the preparation of cyclobutene derivatives bearing an extra heteroatom directly linked to a sp 2 carbon atom of the carbocycle (Scheme 1). These heteroatom-substituted cyclobutenetriflones.…”

Section: Introductionmentioning

confidence: 99%

Regioselective Synthesis of Heteroatom‐Functionalized Cyclobutene‐triflones and Cyclobutenones

2017

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The controlled metal-free synthesis of a vast variety of heteroatom-containing cyclobutene-triflones and cyclobutenones has been developed starting from heteroatomsubstituted alkynes and a pyridinium salt (a latent Tf2C=CH2 source). This powerful methodology, involving cyclization reactions allows for the selective preparation of oxygen-, nitrogen-, bromine-, chlorine-, iodine-, sulphur-, selenium-, tellurium-, phosphorus-, and silicon-functionalized cyclobutene derivatives.

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Unveiling the uncatalyzed reaction of alkynes with 1,2-dipoles for the room temperature synthesis of cyclobutenes

Abstract: 2-(Pyridinium-1-yl)-1,1-bis(triflyl)ethanides have been used as 1,2-dipole precursors in a metal-free direct [2+2] cycloaddition reaction of alkynes. Remarkably, this mild and facile uncatalyzed protocol requires neither irradiation nor heating.

Cited by 39 publications

References 19 publications

Synthesis and Characterization of Stable Phosphorus Carbabetaines

Synthesis and Characterization of Stable Phosphorus Carbabetaines

Cyclobutene vs 1,3-Diene Formation in the Gold-Catalyzed Reaction of Alkynes with Alkenes: The Complete Mechanistic Picture

Regioselective Synthesis of Heteroatom‐Functionalized Cyclobutene‐triflones and Cyclobutenones

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