ISSN:
1434-193X
Keywords:
Pyrolysis
;
1,3-Hexadien-5-ynes
;
Cyclization, radical
;
13C, D labelling
;
Naphthalene isotopomers
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The thermal cycloisomerization of the isotope-labelled 1-phenyl-1-buten-3-ynes 1 {including the [3-13C,4-D]1-phenyl-1-buten-3-yne (6) and the [4-D]1-phenyl-1-buten-3-yne (9) formed as intermediates} has been studied. The investigations were performed in a quartz flow system at a temperature of 650 °C (1, 6) [and over the range 625-750 °C for (9)] at a reaction time of 0.3 s in the presence of different diluent gases (H2, N2, N2-toluene). Spectroscopic analyses of the naphthalene isotopomers formed allow the evaluation of competing radical reaction channels in addition to reactions occuring by electrocyclic and carbene-like ring closure.[1] A mechanistic analysis for the conversion of 1 undoubtedly suggests a predominant reaction course via phenyl-type radical intermediates (1c/6c), followed by their exocyclization to the indenylcarbenyl radicals 1f/6f and the homoallyl-like rearrangement of the latter to the 1,2-dihydronaphthyl radicals 1i/6i at 650 °C. With increasing temperature, other competing reactions (endocyclizations of vinyl- and phenyl-type radicals as well as neophyl-like rearrangements of the indenylcarbinyl radicals 1f/6f) gain in importance.
Type of Medium:
Electronic Resource
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