Photochemische Reaktionen. 118. Mitteilung [1] Zur vinylogen β-Spaltung von Enonen. UV.-Bestrahlung von 4-(3',7',7'-Trimethyl-2'-oxabicyclo [3.2.0]hept-3'-en-1'-yl)but-3-en-2-on

✍ Scribed by Kazuo Murato; Hans Richard Wolf; Oskar Jeger

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: German
• Weight: 557 KB
• Volume: 64
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19810640123

✦ Synopsis

Vinylogous β‐Cleavage of Enones: UV.‐irradiation of 4‐(3′,7′,7′‐trimethyl‐2′‐oxabicyclo[3.2.0]hept‐3′‐ene‐1′‐yl)but‐3‐ene‐2‐on

On ^1^π,π*‐excitation (λ = 254 nm) in acetonitrile (E/Z)‐2 is converted into the isomers 4–9 and undergoes fragmentation yielding 10; in methanol (E/Z)‐2 gives 7–10 and is transformed into 11 by incorporation of the solvent.

On ^1^π,π*‐excitation (λ λ⩾347 nm; benzene‐d~6~) (E)‐2 is isomerized into (Z)‐2, which is converted into the isomers 3 and 4 by further irradiation.

^1^π,π*‐Excitation (λ = 254 nm; acetonitrile) of 4 gives 6 and (E)‐9, whereas UV.‐irradiation (λ = 254 nm; acetonitrile‐d~3~) of 5 yields (E)‐7 and 8.

On ^1^π,π*‐excitation (λ = 254 nm; acetonitrile) of (E/Z)‐12 the compounds (E)‐14 and (E)‐15 are obtained.