New photochemical reactions of α-diketones

✍ Scribed by T.L. Burkoth; Edwin F. Ullman

• Publisher: Elsevier Science
• Year: 1970
• Tongue: French
• Weight: 206 KB
• Volume: 11
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)97661-0

✦ Synopsis

The most general known photochemical reaction of alkyl a-diketones is 2-hydroxycyclobutanone formation.

1 Recent reports2 of alternative photochemical.

pathways of a-diketones prompts us to describe our studies of three new reactions that take place in suitably designed molecules.

Formation of hydroxycyclobutanones from a-diketones probably proceeds by %-hydrogen abstraction through a pseudo six-membered ring transition state.

Although y-hydrogen abstraction should proceed through an equally strain-free pseudo six-membered ring, evidence for this process has not heretofore been obtained.

The absence of y-hydrogen abstraction suggests a statistical preference for a transition state incorporating an sp2 hybridized carbon in the pseudo ring. To determine if y-hydrogen abstraction could occur in a favorably substituted a-diketone, I3 was prepared by acyloin condensation of ethyl yphenylpropionate followed by oxidation with bismuth oxide in acetic acid. 4