Thermal and Base-Induced Cyclizations of N-Heteroarylamidinopropanoates

2004 ◽  
Vol 57 (6) ◽  
pp. 577 ◽  
Author(s):  
Adrian Clark ◽  
Rolf H. Prager
Keyword(s):  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

The potential cyclization of N-heteroarylamidines to annelated pyrimidines by flash vacuum pyrolysis or by treatment with bases has been investigated. The pyrolytic process with the title compounds is complicated by competing formation and rearrangement of an imidoylketene. The major pyrolysis products, the 4-aminopyrimidin-6-ones, were best prepared from the title compounds by reaction with hindered alkoxides, while the pyrolysis byproducts, the 4-alkoxypyrimidin-6-ones, were conveniently prepared from the appropriate isoxazol-5(2H)-one by reaction with the appropriate alkoxide, followed by acidic workup.

Methyleneketenes and methylenecarbenes. I. Formation of arylmethyleneketenes and alkylideneketenes by pyrolysis of substituted 2,2-Dimethyl-1,3-dioxan-4,6-diones

1974 ◽  
Vol 27 (11) ◽  
pp. 2373 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
KJ Harrington
Keyword(s):  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Infrared Measurements

Flash vacuum pyrolysis (430�) of 5-benzylidene-2,2-dimethyl-1,3-dioxan- 4,6-diones gives benzylidene-ketenes which dimerize to form 2,4- bis(benzylidene)cyclobutane 1,3-diones. Diphenylmethylene-,t- butylmethylene- and isopropylidene-2,2-dimethyl-1,3-dioxan-4,6-diones similarly give the substituted methylene ketenes which dimerize to form 2,4-bis(diphenylmethylene)-, 2,4-bis(t-butylmethylene)- and 2,4- bis(isopropylidene)-cyclobutane-1,3-dione respectively. Infrared measurements on the pyrolysis products kept at liquid nitrogen temperature showed absorption near 2100 cm-1 which was attributed to the methyleneketenes. Reaction of the pyrolysates of ethylidene- and isobutylidene-2,2-dimethyl-1,3-dioxan-4,6-diones with aniline vapour yielded but-3-enanilide and 4-methylpent-3-enanilide respectively.

Flash Vacuum Pyrolysis of Some N-Benzylbenzotriazoles and N-Benzylbenzisoxazolones

1998 ◽  
Vol 51 (10) ◽  
pp. 925 ◽  
Author(s):  
Jabbar Khalafy ◽  
Rolf H Prager
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Addition Reactions ◽  
Atom Transfer ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Intramolecular Hydrogen

The flash vacuum pyrolysis products of 2-(benzotriazol-1-ylmethyl)benzonitrile, methyl 2-(benzotriazol-1-ylmethyl)benzoate and the corresponding benzisoxazolones have been characterized. The benzotriazoles lose nitrogen to give diradicals which undergo intramolecular hydrogen-atom transfer or cyclization, while the benzisoxazolones rearrange initially to the corresponding benzaldehyde N-(2-carboxyphenyl)imines which undergo subsequent intramolecular addition reactions.

A Comparison of the Flash Vacuum Pyrolysis Products of Some N-Acylbenzotriazoles and N-Acylbenzisoxazolones

1999 ◽  
Vol 52 (8) ◽  
pp. 775 ◽  
Author(s):  
Mehdi M. Baradarani ◽  
Jabbar Khalafy ◽  
Rolf H. Prager
Keyword(s):  
Low Temperature ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Radical Processes ◽  
Benzotriazole Derivatives

The flash vacuum pyrolysis (f.v.p.) products of 2-(1H-benzotriazol-1-ylcarbonyl)benzonitrile, methyl 2-(1H-benzotriazol-1-ylcarbonyl)benzoate and 1-(2-chloromethylbenzoyl)-1H-benzotriazole and the cor- responding benzisoxazolones have been characterized. The benzotriazole derivatives gave compounds whose origin suggests the predominance of radical processes. At lower temperatures the benzisoxa- zolones gave benzoxazole products consistent with a singlet carbene intermediate, but which had triplet diradical properties at higher temperatures, leading to the formation of acridine from the chloromethyl compound. The major low-temperature f.v.p. product from the (chloromethylbenzoyl)benzisoxazolone was indolo[1,2-b]benzoxazole.

N-Benzylidene-2-nitrobenzenesulfenamide and 1-Nitro-2-(phenylthio)benzene: Comparison of Their Behavior on Flash Vacuum Pyrolysis and Under Electron Impact

1990 ◽  
Vol 43 (10) ◽  
pp. 1779 ◽  
Author(s):  
RG Gillis ◽  
QN Porter ◽  
LL Yeoh
Keyword(s):  
Mass Spectrum ◽  
Electron Impact ◽  
Preparative Thin Layer Chromatography ◽  
Gas Chromatography Mass Spectrometry ◽  
Base Peak ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Electron Impact Mass ◽  
Layer Chromatography

The molecular ion of N-benzylidene-2-nitrobenzenesulfenamide (1) loses SO2 and N2 and gives a base peak at m/z 165, C13H9, and another abundant peak at m/z 166, C13H10. Analysis, by gas chromatography/mass spectrometry and by preparative thin-layer chromatography, of the products of flash vacuum pyrolysis at 500-800°C of (1) showed no detectable hydrocarbon, but dibenzothiophen (mol. wt 184) was isolated and identified. The abundance of m/z 184 in the positive-ion mass spectrum of (1) is about 1%. In the mass spectrum of 1-nitro-2-( phenylthio )benzene (2a) the base peak is at m/z 167, C12H9N, and there is a fragment ion at m/z 184, C12H8S (35%). However, carbazole (3) could not be isolated from the flash vacuum pyrolysis products, but dibenzothiophen (4) was obtained in increasing yield as the pyrolysis temperature was raised from 500 to 800°C. It is clear from these results that drawing analogies between electron impact mass spectra and flash vacuum pyrolysis results is somewhat hazardous.

Methyleneketenes and methylenecarbenes. VII. Evidence for the pyrolytic generation of methyleneketene (propadienone)

1977 ◽  
Vol 30 (1) ◽  
pp. 179 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
GL McMullen
Keyword(s):  
Mass Spectrometry ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Methylene Chloride ◽  
Liquid Nitrogen Temperature ◽  
Pyrolysis Products ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Infrared Measurements ◽  
Methanol Vapour

Oxidation of 2,2,5-trimethyl-5-phenylseleno-1,3-dioxan-4,6-dione with m-chloroperbenzoic acid in methylene chloride gives a solution containing 2,2-dimethylspiro[1,3-dioxan-5,2'-oxiran]-4,6-dione and the unstable 2,2-dimethyl-5-methylene-1,3-dioxan-4,6-dione, which forms stable adducts with cyclohexadiene and cyclopentadiene. Flash vacuum pyrolysis of the cyclopentadiene adduct over the temperature range 460- 570° and detection of the components present in the pyrolysate by mass spectrometry showed that cyclopentadiene, acetone, carbon dioxide and methyleneketene (CH2=C=C=O) are formed; the last breaks down into acetylene and carbon monoxide at higher temperatures (520-570°). Infrared measurements on the pyrolysis products kept at liquid nitrogen temperature showed absorption near 2100 cm-1 which is attributed to methyleneketene. Reaction of the pyrolysate with aniline vapour or methanol vapour yielded acrylanilide and methyl acrylate respectively. Pyrolysis in the absence of trapping agents gave a glassy solid on an uncooled glass surface. This solid is considered to be formed by addition of methyleneketene to 2,2-dimethyl-5-methylene-1,3-dioxan-4,6- dione. Methanolysis of the solid and esterification with diazomethane gave dimethyl 2-methoxycarbonyl-4-methylenepentanedioate.

Sulfonyl isocyanides RSO2NC

2017 ◽  
Author(s):  
Curt Wentrup ◽  
Horst Briehl
Keyword(s):  
Ir Spectrum ◽  
Reaction Conditions ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

Flash vacuum pyrolysis (FVP) of 5-azido-1-aryltetrazoles results in triple N<sub>2</sub> elimination and formation of aryl isocyanides RNC, which rearrange in part to aroylnitriles RCN under the reaction conditions. Similar FVP of 5-azido-1-arenesulfonyltetrazoles generates a compound absorbing in the IR spectrum (77 K) at 2090 cm<sup>-1 </sup>and assigned the structure of arenesulfonyl isocyanide, ArSO<sub>2</sub>NC <b>11</b>. FVP at temperatures above 600 <sup>o</sup>C results in progressively more nitrile ArSO<sub>2</sub>CN <b>12</b>. Compound <b>11</b> also disappears on warming above -80 <sup>o</sup>C

Sulfonyl isocyanides RSO2NC

2017 ◽  
Author(s):  
Curt Wentrup ◽  
Horst Briehl
Keyword(s):  
Ir Spectrum ◽  
Reaction Conditions ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

Flash vacuum pyrolysis (FVP) of 5-azido-1-aryltetrazoles results in triple N<sub>2</sub> elimination and formation of aryl isocyanides RNC, which rearrange in part to aroylnitriles RCN under the reaction conditions. Similar FVP of 5-azido-1-arenesulfonyltetrazoles generates a compound absorbing in the IR spectrum (77 K) at 2090 cm<sup>-1 </sup>and assigned the structure of arenesulfonyl isocyanide, ArSO<sub>2</sub>NC <b>11</b>. FVP at temperatures above 600 <sup>o</sup>C results in progressively more nitrile ArSO<sub>2</sub>CN <b>12</b>. Compound <b>11</b> also disappears on warming above -80 <sup>o</sup>C

Characterization of Vacuum Pyrolysis Products from Phenolic Resin Laminate Substrate

2010 ◽  
Vol 38 (1) ◽  
pp. 72-76
Author(s):  
Wen-Biao WU ◽  
Ke-Qiang QIU ◽  
Cheng-Long LI ◽  
Xiao-Qun XU
Keyword(s):  
Phenolic Resin ◽  
Pyrolysis Products ◽  
Vacuum Pyrolysis
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