RESUMO
Herein, a photocatalytic Giese-type reaction with alkylsilicates bearing C,O-bidentate ligands as stable alkyl radical precursors has been reported. The alkylsilicates were prepared in one step from organometallic reagents. Not only primary, secondary, and tertiary alkyl radicals, but also elusive methyl radicals, could be generated by using the present reaction system. The generated radicals were trapped by electron-deficient olefins bearing various functional groups to give the desired alkyl adducts. The silicon byproduct can be recovered after the photoreaction. The radical generation process was investigated by theoretical calculations, which provided an insight into the facile generation of methyl radicals from methylsilicate bearing C,O-bidentate ligands.
RESUMO
We report the photocatalytic C-H alkylations of heteroarenes with alkylsilicates bearing C,O-bidentate ligands under acidic conditions. Irradiation of heteroaromatics in the presence of the silicates and trifluoroacetic acid produced the corresponding alkylated compounds. The present reaction system does not require any terminal oxidant although the reaction seems to be a formal oxidation reaction. This study demonstrates that alkylsilicates can be used in photocatalytic radical chemistry under acidic conditions.
RESUMO
We report the photocatalytic C-H amination of aromatics overcoming redox potential limitations. Radical cations of aromatic compounds are generated photocatalytically using Ru(phen)3(PF6)2, which has a reduction potential at a high oxidation state (Ered(RuIII/RuII) = +1.37 V vs SCE) lower than the oxidation potentials of aromatic substrates (Eox = +1.65 to +2.27 V vs SCE). The radical cations are trapped with pyridine to give N-arylpyridinium ions, which were converted to aromatic amines.
