Photoreduction of Cyclic α-Fluoroketones

Article abstract of DOI:10.1002/hlca.19830660819

Irradiation of the α-fluoroketones 1a and 6a in i-PrOH selectively affords the parent ketone 1b and 6b, respectively.It is concluded that in this solvent heterolytic C-F bond cleavage of the radical -formed by electron transfer to the excited fluoroketone- is a faster process than the subsequent protonation by the cation radical of the solvent.In cyclohexane 1b and 6b are only formed a minor amounts, the fluorinated RH-reduction product 4 now being the major product from 1a.In non-reducing solvents as t-BuOH or benzene 2-fluorocyclohexanone (1a) exhibits a similar behavior as cyclohexanone (1b) on excitation.The quantum yields for α-cleavage are alike for both compounds, but oxetane formation with 2-methylpropene as olefinic component occurs much more readily with 1a than with 1b.