Electrophotocatalytic Si-H Activation Governed by Polarity-Matching Effects

Trialkylsilanes are important building blocks in organic synthesis; however, their widespread use in redox chemistry is limited by their high oxidation potentials and comparably high bond dissociation energies (BDEs) of Si-H and alpha-Si-C-H bonds (>92 kcal mol(-1)). Herein, we report a new strategy for Si-H bond homolysis enabled by the synergistic combination of electrooxidation, photoinduced ligand-to-metal charge transfer (LMCT), and radical-mediated hydrogen atom transfer (HAT). Governed by the polarity-matching effect, the HAT to electrophilic MeO. or [Cl-OHCH3] from the more hydridic Si-H instead of a C-H bond allows the selective generation of silyl radicals. This electrophotocatalytic protocol provides rapid access to Si-functionalized benzimidazo-fused isoquinolinones with broad functional-group compatibility. Mechanistic studies have shown that n-Bu4NCl is essential to the electrooxidation of CeCl3 to form the Ce(IV) species. [GRAPHICS] .

Automated summary

This study reports a new strategy for homolysis of Si-H bonds using electrooxidation, photoinduced ligand-to-metal charge transfer, and radical-mediated hydrogen atom transfer. This method provides rapid access to Si-functionalized benzimidazo-fused isoquinolinones with broad functional-group compatibility.