79238-27-0Relevant articles and documents
PHOTOCHEMISTRY OF β,γ-UNSATURATED KETONES - V ; THE DIRECT IRRADIATION OF SOME γ-PHENYL β;γ-ENONES
Weerdt, Anton J. A. Van Der,Cerfontain, Hans
, p. 2121 - 2130 (2007/10/02)
The photochemistry of some members of the two series of γ-phenyl substituted acyclic β,γ-unsaturated ketones 1 and 2 upon direct irradiation with λ 310 nm has been investigated, viz 1c-1h and 2b+2c.The alkyl substituted (E)-5-phenyl-4-penten-2-ones 1c-1h yield the corresponding 1,3-acyl shift products and (Z)-isomers, and 1g and 1h in addition two decarbonylated products. 2b only yields the (Z)-isomer and some benzaldehyde, but 2c yields the 1,3-acyl shift product, the ODPM product, three hydrocarbons formed by disproportionation of the allyl radical, and some benzaldehyde.The β-phenyl β,γ-UK 3a proved to be photostable.The 1,3-acyl shift products of 1c-1h result mainly from the singlet excited state in a cage radical process.The exclusive formation of the (E)-configuration of the 1,3-acyl shift product is explained in terms of conformational preference of the intermediate allyl radical.It is proposed that the formation of the (Z)-isomer proceeds from 1T(?-?*) which is populated according to .Evidence is presented which supports the proposed mechanism.The β,γ-UK 2b containing a benzoyl moiety leads to a higher degree of (E)-(Z) isomerization than the corresponding 1d which has an acetyl moiety.The triplet energies of (E)- and (Z)-1h are 56 and ca 70 kcal/mol respectively.
