Isolierbare cyclobutadiene-VI. 1,2,3,4-tetra-tert.butylbenzol, 2,3,4,5-tetra-tert.butylbiphenyl, 2,3,4,5-tetra-tert.butylpyridin und 2,3,4,5-tetra-tert.butylfuran

Krebs, Adolf; Franken, Erhard; Müller, Sigrid

doi:10.1016/s0040-4039(01)90408-3

Cited by 21 publications

(4 citation statements)

References 7 publications

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“…The 1 H NMR spectra of 6 – 8 in CDCl 3 exhibit classical features of other phenyl‐substituted carbo ‐benzenes, namely, a strong deshielding of the ortho ‐ 1 H nuclei at δ =9.5–9.6 ppm due to the diatropic ring current over the C 18 macrocycle . The t Bu 1 H nuclei of 5 – 8 also resonate at relatively low field ( δ ≈2.5 ppm; Figure ), with chemical shifts deshielded by 1 ppm with respect to those of 1,2,3,4‐ and 2,3,4,5‐tetra‐ tert ‐butylbenzene ( δ =1.27–1.49 ppm) . Notably, hexa‐ tert ‐butylbenzene, which is the parent of 5 , has been studied at the theoretical level only .…”

Section: Resultsmentioning

confidence: 89%

“…[1b, 4, 6, 13, 25] The tBu 1 Hn uclei of 5-8 also resonate at relativelyl ow field( d % 2.5 ppm;F igure 2), [8] with chemicals hifts deshielded by 1ppm with respect to those of 1,2,3,4-a nd 2,3,4,5-tetra-tertbutylbenzene (d = 1.27-1.49 ppm). [26] Notably,h exa-tert-butylbenzene, which is the parentof5,has been studied at the theoreticall evel only. [27] The magnetic aromaticity of 5-8 has been scrutinized in more detail by NICS calculations (see Section 2.7).…”

Section: Syntheses Of Pericyclynediols 9-12 and Carbo-benzenes 5-8mentioning

confidence: 99%

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Steric/π‐Electronic Insulation of the carbo‐Benzene Ring: Dramatic Effects of tert‐Butyl versus Phenyl Crowns on Geometric, Chromophoric, Redox, and Magnetic Properties

Listunov

Duhayon

Poater

et al. 2018

Chemistry A European J

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Hexa-tert-butyl-carbo-benzene (C tBu ) and three phenylated counterparts (C tBu Ph ; m=4, 2) have been synthesized. The peralkylated version (m=6) provides experimental access to intrinsic features of the insulated C core independently from the influence of π-conjugated substituent. Over the series, structural, spectroscopic, and electrochemical properties are compared with those of the hexaphenylated reference (m=0). Anchoring tBu substituents at the C macrocycle is shown to enhance stability and solubility, and to dramatically modify UV/Vis absorption and redox properties. Whereas all carbo-benzenes reported previously were obtained as dark-reddish/greenish solids, crystals and solutions of C tBu happen to be yellow (λ =379 vs. 472 nm for C Ph ). In comparison to C Ph , the reduction of C tBu remains reversible, but occurs at twice as high an absolute potential (E =-1.36 vs. -0.72 V). Systematic XRD analyses and DFT calculations show that the C ring symmetry is the nearest to D for m=6, which indicates a maximum geometric aromaticity. According to calculated nucleus-independent chemical shifts (NICS), the macrocyclic magnetic aromaticity is also maximum for C tBu : NICS(0)=-17.2 ppm versus (-18.0±0.1) ppm for the theoretical references C H and C F , and -13.5 ppm for C Ph . Accurate correlations of NICS(0) with experimentally recorded or calculated maximum UV/Vis absorption wavelengths, λ , and chemical hardness, η=E -E , are evidenced.

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Section: Resultsmentioning

confidence: 89%

Section: Syntheses Of Pericyclynediols 9-12 and Carbo-benzenes 5-8mentioning

confidence: 99%

Steric/π‐Electronic Insulation of the carbo‐Benzene Ring: Dramatic Effects of tert‐Butyl versus Phenyl Crowns on Geometric, Chromophoric, Redox, and Magnetic Properties

Listunov

Duhayon

Poater

et al. 2018

Chemistry A European J

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“…To assess the accuracy of such methods, the structures and energies of various isomers and conformers of four known poly( tert -butyl)arenes and related compounds were calculated: 1,2,3,4-tetra( tert -butyl)benzene ( 4 , Table ), hexakis(trimethylsilyl)benzene ( 7 ), dimethyl 3,4,5,6-tetra( tert -butyl)phthalate ( 8 ), and 1,2,3,4-tetra( tert -butyl)naphthalene ( 9 ). Compounds 4 , 7 , and 9 preferentially exist as ordinary arenes, but benzene 8 undergoes thermal isomerization to one of its Dewar isomers . The Dewar isomers of 7 and 9 are also known but revert thermally to the arene, as expected. , To be useful, a computational method must reproduce the known relative stabilities of the valence isomers of these crowded arenes.…”

Section: Resultsmentioning

confidence: 84%

Synthesis of an Extremely Crowded Naphthalene via a Stable Norbornadienone

Zhang

Pascal

2001

J. Am. Chem. Soc.

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Computational studies at the HF/3-21G and B3LYP/6-31G(d) levels suggest that 5,6,8-tri(tert-butyl)-1,2,3,4-tetraphenylnaphthalene (2) is perhaps the most crowded naphthalene derivative that will show normal stability; more highly congested naphthalenes will prefer to exist as the corresponding Dewar isomers. Initial attempts to prepare 2 by reacting 3,4,5,6-tetraphenylbenzyne with 2,3,5-tri(tert-butyl)cyclopentadienone at 83 degrees C gave instead a stable norbornadienone, 1,2,4-tri(tert-butyl)-5,6,7,8-tetraphenyl-9-oxo-1,4-dihydro-1,4-methanonaphthalene (3), which was characterized by X-ray crystallography. The experimental and calculated (HF/3-21G) activation energies (E(a)) for the decarbonylation of 3 were quite high: 39 and 46 kcal/mol, respectively, a manifestation of the substantially increased strain in the transition state as the tert-butyl groups are forced together. The naphthalene 2 was obtained in good yield by heating 3 in refluxing toluene, and its X-ray structure showed exceptional distortions from a normal naphthalene geometry. However, 2 is not completely stable, and it decomposes upon prolonged heating in xylenes.

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“…Alle Befunde sind im Einklang mit der Annahme, daû die Bildung der 1k 5 ,3k 5 -Diphosphinine u È ber eine [2 + 2]-Cycloaddition mit nachfolgender spontaner Valenzisomerisierung verla È uft. Ein analoger Reaktionsmechanismus wird bei der Reaktion zwischen Cyclobutadienen und Nitrilen zu Pyridinen beobachtet [9]. Er entspricht auch der Cycloaddition-CycloreversionsFolge bei der Umsetzung von Phosphoryliden mit Acetylendicarbonsa È uredimethylester zu vinylsubstituierten Yliden [10].…”

Section: Introductionunclassified

Neue 1λ5, 3λ5-[1,3]Diphosphinine mit Thio- und Selenophosphonsäureresten - Darstellung, Kristallstruktur, NMR-Daten und Komplexbildung mit PdII

Plank

Heckmann

Schwarz

et al. 1999

Z. anorg. allg. Chem.

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Inhaltsu È bersicht. Die Darstellung von N,N,N',N'-Tetraethyl-P-(phenylethinyl)phosphono-thiosa È ure-diamid (2) und des entsprechenden Phosphonoselenosa È ure-diamids (3) wird beschrieben. Mit 1,1,3,3-Tetrakis(dimethylamino)-1k 5 ,3k 5 -diphosphet (1) reagieren 2 und 3 zu den 1k 5 ,3k 5 -[1,3]Di-phosphininderivaten 4 und 5. 5 bildet mit (Bzl) 2 Cl 2 Pd die Koordinationsverbindung 6. Alle neuen Verbindungen 2±6 werden durch ihre NMR-und IR-Spektren charakterisiert und die Strukturen von 4±6 durch Kristallstrukturanalysen belegt.Diphosphabenzenes. VI. New 1k 5 , 3k 5 -[1,3]Diphosphinines with Thio and Seleno Phosphonic Acid Groups ± Preparation, Crystal Structure, NMR Data, and Coordination to Pd II Abstract. Preparation of N,N,N',N'-tetraethyl-P-phenylethinyl phosphonothioacid diamide (2) and the corresponding phosphonoselenoacid diamide (3) are described. 2 and 3 react with 1,1,3,3-tetrakis(dimethylamino)-1k 5 ,3k 5 -diphosphete (1) to yield 1k 5 ,3k 5 -[1,3]diphosphinine derivatives 4 and 5. With (bzl) 2 Cl 2 Pd 5 forms the coordination compound 6. All new compounds 2±6 are characterized by their nmr and ir spectra, the structures of 4±6 are further elucidated by X-ray structural analyses. Keywords: 1k 5 ,3k 5 -Diphosphete; 1k 5 ,3k 5 -[1,3]Diphosphinine; Phenylethinyl phosphonothioic diamide; Phenylethinyl phosphonoselenoic diamide; Palladium(II) complex of [1,3]diphosphinine derivative; n.m.r, ir spectra; X-ray structure Einleitung Wie wir in einer Reihe von Untersuchungen [1±7] zeigen konnten, erlaubt die Umsetzung von 1k 5 ,3k 5 -Diphospheten mit Acetylen und Acetylenderivaten einen einfachen Zugang zu 1k 5 ,3k 5 -Diphosphininen. Elektronenarme CºC-Bindungssysteme wie Acetylendicarbonsa È ureester [3, 4, 8] oder Trifluormethylacetylen [3] reagieren mit 1,1,3,3-Tetrakis(dimethylamino)-1k 5 ,3k 5 -diphosphet (1) schon in der Ka È lte sehr rasch, wa È hrend elektronenreichere Systeme wie Tolan [4] in siedendem Toluol Reaktionszeiten von mehreren Ta-gen bis zur vollsta È ndigen Umsetzung beno È tigen. Alle Befunde sind im Einklang mit der Annahme, daû die Bildung der 1k 5 ,3k 5 -Diphosphinine u È ber eine [2 + 2]-Cycloaddition mit nachfolgender spontaner Valenzisomerisierung verla È uft. Ein analoger Reaktionsmechanismus wird bei der Reaktion zwischen Cyclobutadienen und Nitrilen zu Pyridinen beobachtet [9]. Er entspricht auch der Cycloaddition-Cycloreversions-Folge bei der Umsetzung von Phosphoryliden mit Acetylendicarbonsa È uredimethylester zu vinylsubstituierten Yliden [10].Mit phosphorsubstituierten Acetylenen bildet 1 phosphorsubstituierte 1k 5 ,3k 5 -Diphosphinine, die ungewo È hnliche Liganden in Metallkomplexen darstellen [7,11]. Um die Kenntnisse u È ber Liganden dieser Art und ihre komplexbildenden Eigenschaften zu erwei-1712

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Isolierbare cyclobutadiene-VI. 1,2,3,4-tetra-tert.butylbenzol, 2,3,4,5-tetra-tert.butylbiphenyl, 2,3,4,5-tetra-tert.butylpyridin und 2,3,4,5-tetra-tert.butylfuran

Cited by 21 publications

References 7 publications

Steric/π‐Electronic Insulation of the carbo‐Benzene Ring: Dramatic Effects of tert‐Butyl versus Phenyl Crowns on Geometric, Chromophoric, Redox, and Magnetic Properties

Steric/π‐Electronic Insulation of the carbo‐Benzene Ring: Dramatic Effects of tert‐Butyl versus Phenyl Crowns on Geometric, Chromophoric, Redox, and Magnetic Properties

Synthesis of an Extremely Crowded Naphthalene via a Stable Norbornadienone

Neue 1λ5, 3λ5-[1,3]Diphosphinine mit Thio- und Selenophosphonsäureresten - Darstellung, Kristallstruktur, NMR-Daten und Komplexbildung mit PdII

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