Hydrofluoromethylation of alkenes with fluoroiodomethane and beyond.

ABSTRACT

A process for the direct hydrofluoromethylation of alkenes is reported for the first time. This straighforward silyl radical-mediated reaction utilises CH2FI as a non-ozone depleting reagent, traditionally used in electrophilic, nucleophilic and carbene-type chemistry, but not as a CH2F radical source. By circumventing the challenges associated with the high reduction potential of CH2FI being closer to CH3I than CF3I, and harnessing instead the favourable bond dissociation energy of the C-I bond, we demonstrate that feedstock electron-deficient alkenes are converted into products resulting from net hydrofluoromethylation with the intervention of (Me3Si)3SiH under blue LED activation. This deceptively simple yet powerful methodology was extended to a range of (halo)methyl radical precursors including ICH2I, ICH2Br, ICH2Cl, and CHBr2F, as well as CH3I itself; this latter reagent therefore enables direct hydromethylation. This versatile chemistry was applied to 18F-, 13C-, and D-labelled reagents as well as complex biologically relevant alkenes, providing facile access to more than fifty products for applications in medicinal chemistry and positron emission tomography.