Photochemische Reaktionen. 97 Mitteilung [1]. Zur Photochemie konjugierter Epoxy-diene II. Versuche mit (E)-β-Jonyliden-epoxiden

✍ Scribed by Alex Peter Alder; Hans Richard Wolf; Oskar Jeger

• Publisher: John Wiley and Sons
• Year: 1978
• Tongue: German
• Weight: 923 KB
• Volume: 61
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19780610737

✦ Synopsis

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.