Bond-shift isomers: the co-existence of allenic and propargylic phenylnitrile imines

Nunes, Cláudio M.; Reva, Igor; Fausto, Rui; Bégué, Didier; Wentrup, Curt

doi:10.1039/c5cc03518j

Cited by 37 publications

(83 citation statements)

References 42 publications

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“…The 1734 cm –1 band could correspond to the strongest calculated band of the diazirine 4b (1718 cm –1 , B3LYP/6‐311++G(3df,3dp)). Weak absorptions similar to this, often broad or structured, have been observed for several 1 H ‐diazirines , , . However, the band is too weak to allow the detection of other infrared bands potentially belonging to the diazirine, and the attribution must, therefore, remain tentative.…”

Section: Resultssupporting

confidence: 87%

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Photolysis and Pyrolysis of Phenyltetrazoles: Formation of Phenylcarbodiimide, N‐Phenylnitrile Imine, Phenylnitrene, Indazole, and Fulvenallene

et al. 2019

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Photolysis of 1‐phenyltetrazole 2b at either 193 or 266 nm in a Ne matrix as well as flash vacuum pyrolysis (FVP) of the same compound with isolation of the products in Ne matrix generate phenylcarbodiimide PhN=C=NH 6 very efficiently as the principal product in an almost pure state. Minor amounts of phenyl azide 8 and 1‐azacyclohepta‐1,2,4,6‐tetraene 10, the product of ring expansion of phenylnitrene, are also formed, and the amounts of both substances increase as a function of photolysis time. The photolysis of 2‐phenyltetrazole 1b in a Ne matrix at 266 nm for 0.5 min generates the allenic N‐phenylnitrile imine PhN=N(+)=CH(–) 3b, absorbing strongly and cleanly at 2021 cm–1 in the IR spectrum. At longer photolysis times peaks ascribed to phenyl azide, phenylnitrene, 1‐azacycloheptatetraene, and phenylcarbodiimide 6 become prominent. FVP of 2‐phenyltetrazole yields indazole 15 as the major product together with a small amount of phenylcarbodiimide 6. Indazole formation is ascribed to cyclization of the nitrile imine in the ground state. It is not formed on FVP of 1‐phenyltetrazole in agreement with the computational result that the thermodynamically most favourable path for rearrangement of the putative N‐phenylimidoylnitrene 5b yields phenylcarbodiimide 6 rather than phenylnitrile imine 3b. Further pyrolysis of indazole affords a minor yield of fulvenallene 18.

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Section: Resultssupporting

confidence: 87%

“…The photolysis of 2b is expected to lead initially to the open‐shell singlet imidoylnitrene 5b , which rearranges rapidly to phenylcarbodiimide 6 , i.e. the same product as obtained from 1a , . The carbodiimide 6 is known to isomerize in part to phenylcyanamide 7 on matrix photolysis , .…”

Section: Resultsmentioning

confidence: 99%

Photolysis and Pyrolysis of Phenyltetrazoles: Formation of Phenylcarbodiimide, N‐Phenylnitrile Imine, Phenylnitrene, Indazole, and Fulvenallene

et al. 2019

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“…[37] Geometry optimizations were followed by vibrational frequency calculations, which allowed characterization of the nature of stationary points. [38] The scaling procedure was applied to correct for vibrational anharmonicity, basis set truncation, and the neglected part of the electron correlation. The animation of the normal coordinates associated with the imaginary frequencies shows the expected reaction coordinates.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

On the Photochemistry of 1,2‐Benzisoxazole: Capture of Elusive Spiro‐2H‐azirine and Ketenimine Intermediates

et al. 2016

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The photochemistry of 1,2‐benzisoxazole (1) was studied using low‐temperature matrix isolation coupled with infrared spectroscopy and quantum chemistry calculations. We identified, for the first time, spiro‐2H‐azirine 2 and ketenimine 3 as intermediates in the photoisomerization of 1 to 2‐cyanophenol (4). These results constitute indirect evidence for the existence of vinylnitrene intermediates in the photochemistry of 1,2‐benzisoxazoles. The potential energy surface (PES) resulting from the N–O bond cleavage of 1 was compared with the respective PES of the parent isoxazole. Calculations at the CBS‐QB3 level show that no stabilization is gained for the triplet vinylnitrene upon introduction of a benzene ring fused with isoxazole. However, the energies of 2 and 3 are higher by 13–15 kcal/mol comparing with the 2H‐azirine and ketenimine analogs resulting from isoxazole, which explains why they had not been observed before. Our general mechanistic proposal also predicts well the photoisomerizations of 2 and 3 to 4.

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“…Einige Nitrilimine,w ie die C-Alkylund C-Aryl-N-silylnitrilimine 86,sind allerdings stabil genug, dass sie mittels FVP bei 400-500 8 8Chergestellt [Gl. [58,155,156] Nitrilimine lagern sich bei hçheren Te mperaturen in Carbodiimide 88 um [Gl. [58] Sie wurden durch Online-MS und -PES sowie Tieftemperatur-IR-Spektroskopie charakterisiert, wodurch sie sich klar von den isomeren Diazoverbindungen und Carbodiimiden unterscheiden lassen.…”

Section: Angewandte Chemieunclassified

“…[58] Sie wurden durch Online-MS und -PES sowie Tieftemperatur-IR-Spektroskopie charakterisiert, wodurch sie sich klar von den isomeren Diazoverbindungen und Carbodiimiden unterscheiden lassen. [156] Des Weiteren wurden Nitril-Ylide RCN + C À R'R" durch FVP generiert. [58,155,156] Nitrilimine lagern sich bei hçheren Te mperaturen in Carbodiimide 88 um [Gl.…”

Section: Angewandte Chemieunclassified

Flash‐Vakuumpyrolyse – Techniken und Reaktionen

Wentrup

2017

Angewandte Chemie

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Die Anfänge der Flash‐Vakuumpyrolyse (FVP) ergaben sich in den 1940er und 1950er Jahren hauptsächlich aus dem massenspektrometrischen Nachweis pyrolytisch entstandener freier Radikale. In den 1960er Jahren begannen Organiker mit der Durchführung von FVP‐Experimenten zum Zweck der Isolierung neuer und interessanter Verbindungen und zum Verständnis pyrolytischer Prozesse. Seitdem wurden viele unterschiedliche Typen von Apparaten und Techniken entwickelt. Zielsetzung dieses Aufsatzes ist es, die wichtigsten Methoden vorzustellen wie auch eine Übersicht über typische Reaktionen und Beobachtungen zu geben, die mit den verschiedenen Techniken erreicht werden können. Dies umfasst unter anderem präparative FVP, chemische Abfangreaktionen, Matrixisolierung sowie Tieftemperatur‐Spektroskopie reaktiver Intermediate und instabiler Moleküle. Darüber hinaus ist die Kombination von FVP mit Matrixisolierung und Photochemie ein wirkungsvolles Instrument für Untersuchungen von Reaktionsmechanismen.

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Bond-shift isomers: the co-existence of allenic and propargylic phenylnitrile imines

Cited by 37 publications

References 42 publications

Photolysis and Pyrolysis of Phenyltetrazoles: Formation of Phenylcarbodiimide, N‐Phenylnitrile Imine, Phenylnitrene, Indazole, and Fulvenallene

Photolysis and Pyrolysis of Phenyltetrazoles: Formation of Phenylcarbodiimide, N‐Phenylnitrile Imine, Phenylnitrene, Indazole, and Fulvenallene

On the Photochemistry of 1,2‐Benzisoxazole: Capture of Elusive Spiro‐2H‐azirine and Ketenimine Intermediates

Flash‐Vakuumpyrolyse – Techniken und Reaktionen

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