Flash-vacuum pyrolysis of N-vinylbenzotriazoles: formation of N-phenylketenimines

Maquestiau, A.; Beugnies, Didier; Flammang, Robert; Katritzky, Alan R.; Soleiman, Mohammed; Davis, Terry C.; Lam, Jamshed N.

doi:10.1039/p29880001071

Cited by 30 publications

(7 citation statements)

References 3 publications

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“…392 More recent FVP studies demonstrate that indole 455 and N-phenylketenimine 456 are primary products formed in concurrent, parallel reactions (Scheme 60). 31,393 In contast, the sequential formation of N-phenylketenimine and indole in the FVP of 1-vinylbenzotriazole claimed by Katritzky, Maquestiau, and their co-workers 394 has been shown to be erroneous. 31 Following FVP at 900 °C, nearly all of the 1-vinylbenzotriazole was consumed, but phenylacetonitrile 458 had now replaced N-phenylketenimine.…”

Section: 23-triazolesmentioning

confidence: 99%

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

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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Section: 23-triazolesmentioning

confidence: 99%

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

2017

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“…Mass spectroscopy studies of flash-vacuum pyrolysis of β-substituted 1-vinylbenzotriazoles 1270 (Scheme ) suggest that the compounds, initially formed at 500−700 °C, are the corresponding N -phenylketenimines 1271 , which under more drastic conditions (∼800 °C) isomerize into indoles . Pyrolysis of 1270c at 800 °C gives 2- and 3-phenylindole 403 while of 1270d affords only 3-pentylindole …”

Section: Thermolysis (Graebe−ullmann Reaction) and Photolysis: Loss ...mentioning

confidence: 99%

“…Mass spectroscopy studies of flash-vacuum pyrolysis of β-substituted 1-vinylbenzotriazoles 1270 (Scheme 392) suggest that the compounds, initially formed at 500-700 °C, are the corresponding N-phenylketenimines 1271, which under more drastic conditions (∼800 °C) isomerize into indoles. 403 Pyrolysis of 1270c at 800 °C gives 2-and 3-phenylindole 403 while of 1270d affords only 3-pentylindole. 404 Amide 1272 is obtained as the only product in the flash-vacuum pyrolysis of 1270b, which supports the formation of a ketenimine in the pyrolysis of 1-vinylbenzotriazoles with an R-vinyl hydrogen.…”

Section: Bt−c−carbazole Derivativesmentioning

confidence: 99%

Properties and Synthetic Utility ofN-Substituted Benzotriazoles

et al. 1998

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“…The century old classical Graebe−Ullmann synthesis of carbazoles from 1-arylbenzotriazoles occurs at 360 °C via loss of a nitrogen molecule . Pyrolysis of N -vinylbenzotriazoles at 500−700 °C gave N -phenylketenimines . Recently photodecomposition of tris(benzotriazol-1-yl)methane in benzene gave phenanthridine .…”

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Synthesis of o-Sulfamidotriazobenzenes from 1,1‘-Sulfonylbis(benzotriazole)

Katritzky

Khelashvili

et al. 2007

J. Org. Chem.

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Easily accessible 1,1'-sulfonylbis(benzotriazole) (Bt2SO2, 1) reacts with secondary amines at room temperature to afford (i) the corresponding o-sulfamidotriazobenzenes 2a-d (53-75%) via concurrent substitution of the first and ring opening of the second benzotriazolyl group and (ii) N-sulfonylbenzotriazoles 3b,c,e,f (7-73%). 1-(Morpholine-4-sulfonyl)-1H-benzotriazole 3c reacts with piperidine, pyrolidine, and N-methylpiperazine under microwave irradiation (120 W) at 120 degrees C for 10 min to give the unsymmetrical sulfamides 4a-c (80-90%).

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Flash-vacuum pyrolysis of N-vinylbenzotriazoles: formation of N-phenylketenimines

Abstract: A real-time analysis of the flash-vacuum pyrolysis products of 1 -vinyl-, 1 -(2-methylprop-I -enyl)-, and 1 -styryl-benzotriazole (3), (16), and (18) has been performed by tandem mass spectrometry. In the

Cited by 30 publications

References 3 publications

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Properties and Synthetic Utility ofN-Substituted Benzotriazoles

Synthesis of o-Sulfamidotriazobenzenes from 1,1‘-Sulfonylbis(benzotriazole)

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