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Photochemische Reaktionen. 97 Mitteilung [1]. Zur Photochemie konjugierter Epoxy‐diene II . Versuche mit ( E )‐β‐Jonyliden‐epoxiden
Author(s) -
Alder Alex Peter,
Wolf Hans Richard,
Jeger Oskar
Publication year - 1978
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19780610737
Subject(s) - chemistry , isomerization , cyclopropene , photochemistry , acetone , excitation , photodissociation , conjugated system , stereochemistry , medicinal chemistry , organic chemistry , catalysis , polymer , electrical engineering , engineering
Photolysis of Conjugated Epoxy‐dienes Direct and sensitized excitation of the ( E )‐β‐ionylidene‐epoxides 1 and 4 leads to different types of isomerizations. Thus photocycloelimination to the cyclopropene‐ketones 2 and 6 is only achieved by 1 (π, π*)‐excitation (λ=254 nm), whereas 3 (π, π*)‐excitation (λ > 280 nm, acetone) gives selective C(1′), O‐cleavage of the oxirane ( 1 → 7 – 10 and 4 → 11 – 13 ). In contrast to 1 the twofold methylsubstituted epoxy‐diene 4 shows mainly ( E / Z )‐isomerization ( 4 → 5 ) on both 1 (π, π*)‐ and 3 (π, π*)‐excitation while the isomerizations 4 → 6 and 4 → 11 – 13 are minor processes, only.