Nitrene-Carbene-Carbene Rearrangement. Photolysis and Thermolysis of Tetrazolo[5,1-<i>a</i>]phthalazine with Formation of 1-Phthalazinylnitrene, <i>o-</i>Cyanophenylcarbene, and Phenylcyanocarbene

Høj, Martin; Kvaskoff, David; Wentrup, Curt

doi:10.1021/jo402448u

Section: General Phenomena and Reaction Typesmentioning

confidence: 99%

“…Calculations at the B3LYP/6-31G** level do not indicate the presence of a CN group at all in triplet phenylcyanocarbene ( 3 6), and it is also not observed in the experimental spectrum. 44 A shallow Ph−C−C angle of ca. 160°and equidistant CC and CN bonds in conformity with structure 3 6a are predicted.…”

Section: Nitrenes Are More Stable Than Carbenesmentioning

confidence: 99%

“…1). 44 2-Quinazolinylnitrene is isomeric with 1-phthalazinylnitrene, but there is no experimental evidence for interconversion of the two. Tetrazolo[1,5-a]quinazoline 250 exists exclusively in the tetrazole form 250T at ambient temperature, but the almost pure azide 250A is formed on sublimation at 105 °C, passing the vapor through the FVP tube at 200 °C and isolating the product in an Ar matrix.…”

Section: Chemical Reviewsmentioning

confidence: 99%

See 1 more Smart Citation

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Wentrup

¹

2017

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Flash vacuum pyrolysis (FVP) of azides is an extremely valuable method of generating nitrenes and studying their thermal rearrangements. The nitrenes can in many cases be isolated in low-temperature matrices and observed spectroscopically. NH and methyl, alkyl, aralkyl, vinyl, cyano, aryl and N-heteroaryl, acyl, carbamoyl, alkoxycarbonyl, imidoyl, boryl, silyl, phosphonyl, and sulfonyl nitrenes are included. FVP of triazoloazines generates diazomethylazines and azinylcarbenes, which often rearrange to the energetically more stable arylnitrenes. N elimination from monocyclic 1,2,3-triazoles can generate iminocarbenes, 1H-azirines, ketenimines, and cyclization products, and 1,2,4-triazoles are precursors of nitrile ylides. Benzotriazoles are preparatively useful precursors of cyanocyclopentadienes, carbazoles, and aza-analogues. FVP of 5-aryltetrazoles can result in double N elimination with formation of arylcarbenes or of heteroarylcarbenes, which again rearrange to arylnitrenes. Many 5-substituted and 2,5-disubstituted tetrazoles are excellent precursors of nitrile imines (propargylic, allenic, or carbenic), which are isolable at low temperatures in some cases (e.g., aryl- and silylnitrile imines) or rearrange to carbodiimides. 1,5-Disubstituted tetrazoles are precursors of imidoylnitrenes, which also rearrange to carbodiimides or add intramolecularly to aryl substituents to yield indazoles and related compounds. Where relevant for the mechanistic understanding, pyrolysis under flow conditions or in solution or the solid state will be mentioned. Results of photolysis reactions and computational chemistry complementing the FVP results will also be mentioned in several places.

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“…Interessanterweise wurde nach UV-Bestrahlung sowohl für das reine Alkinyltriazen als auch mit PBN als Spin-Trap ein Signal nachgewiesen. Dies könnte sowohl auf das Vorhandensein eines Triplett-Carbens [16,39] In früheren Berichten wurde NaSO 2 Ph zur Hydrosulfonylierung eines Alkins [40] oder eines Allens verwendet, [35] und es wurden Quenching-Experimente durchgeführt, die die Wechselwirkung zwischen Eosin Y und NaSO 2 Ph zeigten. [35] Nach Anregung von Eosin Y wird aus PhSO Entwicklungen auf diesem Gebiet ebnen werden (auch jenseits der Gold-Katalyse).…”

Section: Methodsunclassified

Lichtinduzierte, metallfreie Erzeugung von Cyanocarbenen aus Alkinyltriazenen für die Synthese von Nitrilderivaten

Michel,

Grieser,

Mackenroth

et al. 2023

Angewandte Chemie

0

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The chemistry of alkynyl triazenes is an emerging field for organic chemists and especially acid‐induced nucleophilic functionalizations, either directly, or after a prior reaction towards aromatic triazenes under extrusion of nitrogen, paved the way for fruitful strategies. In contrast, the chemical behavior of alkynyl triazenes upon irradiation with light is still unknown. Herein we present the first photoactivation of alkynyl triazenes that triggers an uncommon reactivity pattern involving the cleavage of the N1‐N2 bond of the triazene moiety resulting in a unique approach to cyanocarbenes from a readily available, stable, and insensitive precursor. This allows to access various nitrile compounds without the use of a toxic cyanating agent by exploiting the reactivity pattern of carbenes. By variation of the reaction conditions and light sources, different substitution patterns can be obtained selectively in good yields under mild and metal‐free conditions, thus introducing the alkynyl triazene unit as a photo accessible methylene nitrile synthon. Using this synthon, subclasses like α‐alkoxynitriles, α‐aminonitriles and α‐cyanohydrazones become easily available. These exhibit synthetically valuable substitution patterns for the synthesis of pharmaceuticals, intermediates for total synthesis and amino acid synthesis.

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“…Interestingly, after UV irradiation, a signal was detected for both the pure alkynyl triazene and with PBN as a spin-trap. This could indicate both the presence of a triplet-type carbene [16,39] or an underlying radical mechanism. While all of the derived products indicate a carbene like mechanism, a parallel mechanism that is based on radicals at this stage cannot be excluded, hints for such type of side pathway come from another side product that can be explained in accordance with a radical path (dinitrile 6, see Supporting Information for further discussion).…”

Section: Methodsmentioning

confidence: 99%

Light‐Induced Metal‐Free Generation of Cyanocarbenes from Alkynyl Triazenes for the Synthesis of Nitrile Derivatives

Michel,

Grieser,

Mackenroth

et al. 2023

Angew Chem Int Ed

2

0

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The chemistry of alkynyl triazenes is an emerging field for organic chemists and especially acid‐induced nucleophilic functionalizations, either directly, or after a prior reaction towards aromatic triazenes under extrusion of nitrogen, paved the way for fruitful strategies. In contrast, the chemical behavior of alkynyl triazenes upon irradiation with light is still unknown. Herein we present the first photoactivation of alkynyl triazenes that triggers an uncommon reactivity pattern involving the cleavage of the N1‐N2 bond of the triazene moiety resulting in a unique approach to cyanocarbenes from a readily available, stable, and insensitive precursor. This allows to access various nitrile compounds without the use of a toxic cyanating agent by exploiting the reactivity pattern of carbenes. By variation of the reaction conditions and light sources, different substitution patterns can be obtained selectively in good yields under mild and metal‐free conditions, thus introducing the alkynyl triazene unit as a photo accessible methylene nitrile synthon. Using this synthon, subclasses like α‐alkoxynitriles, α‐aminonitriles and α‐cyanohydrazones become easily available. These exhibit synthetically valuable substitution patterns for the synthesis of pharmaceuticals, intermediates for total synthesis and amino acid synthesis.

show abstract

Nitrene-Carbene-Carbene Rearrangement. Photolysis and Thermolysis of Tetrazolo[5,1-a]phthalazine with Formation of 1-Phthalazinylnitrene, o-Cyanophenylcarbene, and Phenylcyanocarbene

Cited by 8 publications

References 41 publications

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Lichtinduzierte, metallfreie Erzeugung von Cyanocarbenen aus Alkinyltriazenen für die Synthese von Nitrilderivaten

Light‐Induced Metal‐Free Generation of Cyanocarbenes from Alkynyl Triazenes for the Synthesis of Nitrile Derivatives

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