Synthesis and reactions of a tetraquinocyclobutane

Köster, Sandra; West, Robert

doi:10.1021/jo00904a007

Cited by 36 publications

(14 citation statements)

References 6 publications

(14 reference statements)

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“…This behavior contrasts strongly with that of the parent hydrocarbon [6]radialene (4), for which in short succession several methods of preparation were published (Scheme 19). @-9, ' ' I While the thermal isomerization of 3,5,9-above, Section 2.2), which allows the preparation of permethyl[6]radialene from 3,4-dibromo-2,5-dimethyl-2,5-hexadiene in excellent yields (63 can be developed further remains to be seen. Sobering is the observation that the diiodide 122 cannot be converted to the hydrocarbon 123,r771 but n 122 123 stimulating the fact that the dibromide 108, which has already been mentioned several times, may be trimerized with (121), which may be prepared from hexakis(bromomethy1)benzene (120) by conventional transf~rmationsl'~] (DDQ = 2,3-dichloro-5,6-dicyano-pbenzoquinone), belongs to the same class of compounds.…”

Section: )mentioning

confidence: 99%

Preparation and Properties, Reactions, and Applications of Radialenes

Hopf

Maas

1992

Angew. Chem. Int. Ed. Engl.

195

164

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The cover picture depicts in the colors of Princeton University two interpenetrating tetrahedra which are nonsuperposable mirror images of each other. According to one of the measures of chirality discussed by Mislow et al. on p. 989ff., these tetrahedra have attained the highest possible degree of asymmetry. Classical asymmetric shapes in organic chemistry result from the tetrdhedral arrangement of four different atoms around a central carbon atom, as illustrated by the ball-and-stick models of the enantiomers above the tetrahedra. The review by Mislow et al. offers a critical discussion of the measures of chirality as well as an up-to-date report on this field-and thus certainly provides food for thought, discussion, and Correspondence. Review ArticlesThe unusual molecular structures and rr-electron systems of radialenes are as much a challenge for preparative chemists as for theoreticians. Two proven methods of synthesis that afford this class of compounds with parent compounds 1-4 are olefin-forming reactions at an existing cycloalkane skeleton and the thermal and metal-induced cyclooligomerization of [n]

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Section: )mentioning

confidence: 99%

Preparation and Properties, Reactions, and Applications of Radialenes

Hopf

Maas

1992

Angew. Chem. Int. Ed. Engl.

195

164

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“…The trimer 4 shows intense absorptions in the visible region of about 400–600 nm which is responsible for its deep coloration. The absorption curve is similar to that of 2 ; the longest absorption band of 4 is 20–30 nm shorter and the second‐longest absorption band is ≈50 nm longer than those of 2 2. The carbonyl stretching of 3 (1586 cm −1 ) is almost similar to that of 1 (1590 cm −1 ), despite the extension of conjugation.…”

Section: Methodsmentioning

confidence: 65%

“…On the other hand, the relatively high values of 2 (1630 cm −1 ), 4 (1617 cm −1 ), 13 (1608 cm −1 ), and 15 (1609 cm −1 )11 are consistent with the order of distortion of the biphenoquinone structures. Because the average twist angle between the quinomethide rings of 2 2 (36°) is the largest in these compounds.…”

Section: Methodsmentioning

confidence: 99%

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A Hexapentaene‐Extended Quinocumulene Cyclotrimerized to a Tricyclobutabenzene Derivative

Kawase¹,

Minami²,

Nishigaki³

et al. 2004

Angew Chem Int Ed

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“…Bereits schwache Verdrillungen eines rr-Systems konnen jedoch die Frank-Condon-Zustande deutlich verschieben und damit den Habitus der langwelligen Banden drastisch verandern "). An Cyaninen ist dabei eine langwellige Verschiebung unter Abnahme des molaren Extinktionskoeffizienten und starke Verbreiterung der Banden nachgewiesen DaB 6 noch den Cyclobutanring enthalt, zeigt das typische 'H-NMR-Signal bei 6 = 5.00; dem Cyanincharakter entsprechen die drei unterschiedlichen 1-Methylpyridiniumsignale im Verhaltnis 1 : 1 : 2 .Es fallt auf, daB die dehydrierende Deprotonierung von 5 in Natronlauge auf der Stufe des Cyanins 6 stehen bleibt und nicht zu14 weiterlauft. Tatsachlich ist 14 als verunreinigtes Farbsalz (A, , , = 632 nm, E = 38000) zu isolieren, wenn 5 in Ethanol/ Natriumethanolat mit Luft dehydriert wird.…”

unclassified

Mehrstufige, reversible Redoxsysteme, XXXII. Pyridylsubstituierte Cyclobutanderivate: Synthese und Redoxreaktionen von Cyaninen sowie Cyclobutenen und ihren Ringöffnungsprodukten

Horner

Hünig

1983

Liebigs Ann. Chem.

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Die Bis(pyridinium)cyclobutane 1 und 3 gehen im basischen Medium durch Luftoxidation in die blauen Cyanine 2 und 4 iiber. Methylierung von 4 fiihrt zum Cyanin 6, das sich auch aus dem Tetrakis(pyridinium)cyclobutan 5 durch oxidative Deprotonierung bildet. 6 steht in einer Natriumethanolat-Losung mit dem ,,Quadratsaurederivai" 14 im Gleichgewicht. Durch Protonierung entsteht aus 6 das Cyclobuten cis-13, das basenkatalysiert in fruns-13 ubergeht. Elektrocyclische Ringoffnung verwandelt stereoselektiv cis-13 in das Butadien Z,E-15 ( t t I 2 = 75 min, 60°C, DMSO) und trans-13 in Z,Z-15 = 6 h, 30"C, DMSO). Unter Redoxkatalyse entsteht aus Z,Z-l5 schliefllich das stabilste lsomere E,E-15. -Die Cyanine 4 , 6 und 14 sind elektrochemisch rweistufig reversibel reduzierbar, aber nur einstufig oxidierbar. 13 ist ein typisches zweistufiges Rcdoxsystem, vergleichbar mit seinem offenkcttigen Analogen 16. Die Butadiene Z,Z-15 und E,E-15 stellen weitere Beispiele fur die seltenen vierstufigen Redoxsysteme dar. Der EinfluO der Pyridiniumgruppen auf das Kedoxverhalten von 4, 6 und 13 -15 wird diskutiert. Multistep, Reversible Redox Systems, XXXIl I). -Pyridyl-substituted Cyclobutane Derivatives: Syntheses and Redox Reactions of Cyanines, Cyclobutenes, and their Ring Opening ProductsBis(pyridinio)cyclobutanes 1 and 3 are transformed by air oxidation in basic media to give the blue cyanines 2 and 4. Methylation of 4 yields the cyanine 6 which also results from oxidative deprotonation of tetrakis(pyridinio)cyclobutane 5. In solutions of sodium ethanolate the cyanine 6 equilibrates with the "squaric acid" derivative 14. Protonation of 6 produces the cyclobutene cis-13 which changes into trans-13 on base catalysis. Electrocyclic ring opening transforms cis-13 stcrcoselectively into the butadiene Z,E-15 (f,,* = 75 min, 60°C, DMSO) and trans-13 into Z,Z-15 (f1,2 = 6 h, 30"C, DMSO). Finally, the most stableisomerE,E-15 is formed from Z,Z-15 by redox catalysis. -The cyanines 4, 6 and 14 are electrochemically reversibly reduced in two steps, but undergo only one-electron oxidations. The cyanine 13 is a typical two-step redox system, comparable to its open-chain analogue 16. The butadienes Z,Z-15 and E,E-15 represent other examples of very rare four-step redox systems. The effect of pyridinium groups on the rcdox properties of 4, 6, and 13 -15 is discussed.

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Synthesis and reactions of a tetraquinocyclobutane

Cited by 36 publications

References 6 publications

Preparation and Properties, Reactions, and Applications of Radialenes

Preparation and Properties, Reactions, and Applications of Radialenes

A Hexapentaene‐Extended Quinocumulene Cyclotrimerized to a Tricyclobutabenzene Derivative

Mehrstufige, reversible Redoxsysteme, XXXII. Pyridylsubstituierte Cyclobutanderivate: Synthese und Redoxreaktionen von Cyaninen sowie Cyclobutenen und ihren Ringöffnungsprodukten

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