Dual N‑Heterocyclic Carbene/Photoredox-Catalyzed Coupling of Acyl Fluorides and Alkyl Silanes

The combination of N-heterocyclic carbene (NHC) organocatalysis
with photochemical activation is becoming increasingly established
as an approach for conducting radical organic reactions under mild
and practical conditions. As comparatively easy to prepare and handle
organic compounds, alkyl silanes are attractive substrates for radical
chemistry as desilylative mesolysis of the corresponding radical cations
is known to be rapid. Here, we report the successful application of
benzyl silane derivatives as source of alkyl radicals in dual NHC/photoredox-catalyzed
radical–radical coupling reactions with acyl fluorides. Relatively
electron-rich benzyl silanes reacted smoothly to afford the corresponding
ketones in generally good yields, while optimization of the NHC and
photocatalyst allowed for a wider scope including primary benzyl substrates.
Furthermore, initial experiments revealed that organosilanes bearing
N-, O- and S-heteroatoms can also serve as alkyl radical sources under
these conditions.