Specifically π→π* Induced Photoreactions of α,β-Unsaturated Ketones: Hydrogen Abstraction by the α-carbon. (Preliminary Communication)

✍ Scribed by Jean Gloor; Gérald Bernardinelli; Raymond Gerdil; Kurt Schaffner

• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: German
• Weight: 260 KB
• Volume: 56
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19730560735

✦ Synopsis

Abstract

Irradiations at 254 nm of the α,β‐unsaturated γ‐dimethoxy‐methyl ketone 7 in iso‐octane and t‐butyl alcohol afforded in a specifically π→π*induced process and in high chemical yield the epimeric products 9 and 10. These products were not formed on n→π* excitation of 7 at > 340 nm, but triplet energy transfer to 1,3‐cyclohexadiene could be observed. Photolyses of the hexadeuterio analog 7‐d~6~ at 254 nm led to the fully deuteriated products (cf. 9‐d~6~) in both solvents, with stereospecific incorporation of a deuterium atom in position C(1α). The structures of 9 and 10 were determined by an X‐ray diffraction analysis of 9 and chemical correlations of the two products. The structural constraints in 7 demand a hitherto unprecedented direct transfer of a methoxyl hydrogen to the α‐carbon of the excited enone and formation of intermediate 8.