Format:
Online-Ressource
ISSN:
1099-0690
Content:
Abstract: The thermally induced ring opening of 1 and 5 proceeds with high stereospecifity in a conrotatory fashion in agreement with the Woodward‐Hoffmann rules. Upon flash pyrolysis of 1 the matrix‐isolated (Xe, 12 K) products 2a and 2b were found, whereas the corresponding reaction of 5 yielded 3a and 3b. The s‐cis conformers 2b and 3b were identified for the first time by comparison of the experimental and calculated (BLYP‐6‐311G*) IR absorptions. A non‐stereospecific photochemical reaction could be observed if matrix‐isolated (Ar or Xe, 12 K) 1 was excited directly with λ = 193 nm. Products of the allowed disrotatory pathway as well as those of the forbidden conrotatory reaction were found, a behaviour that corresponds with the known photochemistry of cyclobutenes. A surprising reaction was found if 1 and 5 were irradiated in a xenon matrix with λ 〉 270 nm. The precursors, which were photostable in an argon matrix, opened the ring in a conrotatory fashion, the expected pathway for a thermal reaction. In this case the light is absorbed by the solid xenon in a cooperative process with the precursor molecules. A detailed discussion of the possible energy transfer mechanisms is given. Most probably, a hot ground‐state reaction of vibrationally excited 1 and 5 occurs, although the reaction of the radical cations cannot be excluded.
In:
volume:1998
In:
number:10
In:
year:1998
In:
pages:2063-2072
In:
extent:10
In:
European journal of organic chemistry, Weinheim : Wiley-VCH Verl., 1998-, 1998, Heft 10 (1998), 2063-2072 (gesamt 10), 1099-0690
Language:
English
DOI:
10.1002/(SICI)1099-0690(199810)1998:10〈2063::AID-EJOC2063〉3.0.CO;2-F
URN:
urn:nbn:de:101:1-2023113005022825485231
URL:
https://doi.org/10.1002/(SICI)1099-0690(199810)1998:10〈2063::AID-EJOC2063〉3.0.CO;2-F
URL:
https://nbn-resolving.org/urn:nbn:de:101:1-2023113005022825485231
URL:
https://d-nb.info/1311686436/34
URL:
https://doi.org/10.1002/(SICI)1099-0690(199810)1998:10〈2063::AID-EJOC2063〉3.0.CO;2-F
Bookmarklink