Enhancement of Through-Space and Through-Bond .pi.-Orbital Interactions. Syntheses and Properties of Permethylated and Perspirocyclopropanated Cyclotetradeca-1,3,6,9,12-pentayne

Scott, Lawrence T.; Cooney, Mark J.; Otte, Carola; Puls, Carsten; Haumann, Thomas; Boese, Roland; Smith, Amos B.; Carroll, Patrick J.; Meijere, Armin de

doi:10.1021/ja00101a051

Cited by 57 publications

(42 citation statements)

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“…The macrocyclization of 22 to 23 was achieved through a modified Eglinton coupling as published by Scott et al [52] To facilitate selective formation of 23, a 0.55 mM solution of 22 in pyridine was added by a syringe pump over the course of 48 h to a solution of 15 equivalents CuCl and 21 equivalents Cu(OAc) 2 in 60 mL of pyridine. After aqueous workup, CC and size exclusion chromatography (BioBeads, SX-3) in toluene, the key intermediate 23 was isolated as a red amorphous solid in 33 % yield.…”

Section: Resultsmentioning

confidence: 99%

A Chiral Macrocyclic Oligothiophene with Broken Conjugation – Rapid Racemization through Internal Rotation

Weiland

Münch

Gschwind

et al. 2018

Helvetica Chimica Acta

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A macrocyclic oligothiophene with an integrated pseudo‐para substituted [2.2]paracyclophane has been achieved. The synthetic sequence relies on alternating steps of halogenation‐ and Suzuki‐coupling conditions. By employing a modified Eglinton reaction under high dilution conditions, the macrocycle is closed and the obtained diacetylene is efficiently transferred to the corresponding thiophene. The molecule is fully characterized and its dynamic racemization is analyzed by variable temperature NMR experiments. The racemization barrier hints with 38 kJ/mol at rapid enantiomerization at room temperature by Mislow’s ‘Euclidian rubber glove’ enantiomerization process. Macrocycle formation results in red‐shifted absorption and emission spectra, hinting at increased conjugation through the oligothiophene versus the trough space conjugation through the [2.2]paracyclophane.

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Section: Resultsmentioning

confidence: 99%

A Chiral Macrocyclic Oligothiophene with Broken Conjugation – Rapid Racemization through Internal Rotation

Weiland

Münch

Gschwind

et al. 2018

Helvetica Chimica Acta

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“…[1,2] Although applications of thiophenes in Diels-Alder reactions have been described, [3] am ore common way to use thiophenes as dienes is after oxidation to the corresponding thiopheneS ,S-dioxides. [4] Although non-stabilized thiophene dioxides easily undergod imerizationr eactions, [5,6] their stabilized analogues are used as dienes in cycloadditions with alkenes [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and alkynes, [22][23][24][25][26][27] mostly under drastic reactionc onditions. However,t he oxidation of thiophenes can be stoppeda tt he sulfoxide stage and the resulting thiopheneS -oxides undergo Diels-Alder reactions under much milder conditions.…”

Section: Introductionmentioning

confidence: 99%

Towards the Design of Optically Active Thiophene S‐Oxides using Quantum Chemistry

Verlinden

Woller

Proft

et al. 2019

Chemistry A European J

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The importance of axially chiral biaryls has risen steeply in the recent decades. This structural motif proved to be successful in catalytic asymmetric synthesis and the configuration of the biaryl axis is decisive for the biological activity. A new approach for the atroposelective synthesis of biaryls would be through a cycloaddition between an enantiopure phenyl‐substituted thiophene S‐oxide and an alkyne. Importantly, the chiral center of the thiophene S‐oxide needs to be stable enough to avoid pyramidal inversion during the cycloaddition. Considering that the racemization of thiophene monoxides has been scarcely investigated so far, we perform a thorough quantum chemical study on the inversion barriers of a large number of chiral thiophene S‐oxide derivatives. Our main goal is to identify substitution patterns leading to stable atropisomers at room temperature. Appealingly, the role of stereoelectronic effects and the position of the substituents as well as the importance of aromaticity on the pyramidal inversion barrier are elucidated for the first time.

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“…In any case, after a flurry of work in the 1950s [8][9][10] and 1970s, [11,12] followed by somewhat of a hiatus, the question of carbyne and polyynes emerged again in the 1990s, sparked in part by marvelous acetylenic structures reported by the groups of, for example, John Gladysz, [13,14] Uwe Bunz, [15,16] Yoshito Tobe, [17,18] Yves Rubin, [19] Larry Scott, [20] and, of course, François Diederich, [21][22][23][24] as well as others. [25] In 1997, I started at the University of Alberta with my own research group, and my thoughts returned quickly to polyynes, and how one might form polyynes.…”

Section: Introductionmentioning

confidence: 99%

“…In any case, after a flurry of work in the 1950s and 1970s, followed by somewhat of a hiatus, the question of carbyne and polyynes emerged again in the 1990s, sparked in part by marvelous acetylenic structures reported by the groups of, for example, John Gladysz, Uwe Bunz, Yoshito Tobe, Yves Rubin, Larry Scott, and, of course, François Diederich, as well as others …”

Section: Introductionmentioning

confidence: 99%

Carbyne: The Molecular Approach

Tykwinski

2015

The Chemical Record

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For the last 60+ years, the synthesis and study of cumulenes and polyynes have been the focus of a small, but dedicated, group of researchers. Many of the remarkable electronic, optical, and structural properties of cumulenes and polyynes had already been identified in the earliest reports. The molecular lengths achievable by the initial syntheses were, unfortunately, somewhat limited by synthetic methods available. For the past 15 years, we have worked toward expanding on the synthesis of cumulenes and polyynes through the development of new methods and stabilization motifs. As new compounds have become available, homologous series of cumulenes and polyynes have then been examined as a function of molecular length. While we are not yet there, we would like to eventually provide a general description of the sp-carbon allotrope carbyne, and this account presents some of our efforts toward this goal.

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Enhancement of Through-Space and Through-Bond .pi.-Orbital Interactions. Syntheses and Properties of Permethylated and Perspirocyclopropanated Cyclotetradeca-1,3,6,9,12-pentayne

Cited by 57 publications

References 0 publications

A Chiral Macrocyclic Oligothiophene with Broken Conjugation – Rapid Racemization through Internal Rotation

A Chiral Macrocyclic Oligothiophene with Broken Conjugation – Rapid Racemization through Internal Rotation

Towards the Design of Optically Active Thiophene S‐Oxides using Quantum Chemistry

Carbyne: The Molecular Approach

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