Electrophotocatalytic Si–H Activation Governed by Polarity-Matching Effects

Abstract

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 α-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-OHCH 3 ]• 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-Bu 4 NCl is essential to the electrooxidation of CeCl 3 to form the Ce (IV) species.

Exploring the regioselectivity of the cyanoalkylation of 3-aza-1,5-dienes: photoinduced synthesis of 3-cyanoalkyl-4-pyrrolin-2-ones

“…Such selectivity might stem from the polar effect. 20 Fig. 1 Examples of 4-pyrrolin-2-one alkaloids.…”

Metal-Free Synthesis of N-Heterocycles via Intramolecular Electrochemical C-H Aminations

“…Recently, organic electrosynthesis has undergone considerable renaissance, and provided unique reactivities that are not accessible with traditional synthetic methodologies. With these benefits, organic electrosynthesis has widely been employed in the construction of C-C ( Pollok and Waldvogel, 2020 ; Zhang et al, 2021 ), C-O ( Herszman et al, 2019 ; Zhang et al, 2019 ), C-S ( Zhang et al, 2020 ) and C-Si ( Ke et al, 2021 ; Jiang et al, 2022 ) bonds in green manners. In the context of intramolecular C-H aminations, organic electrosynthesis has also showed great synthetic potentials.…”

Direct Electrochemical Selenylation/Cyclization of Alkenes: Access to Functionalized Benzheterocycles

“…In the past few years, electrochemistry has emerged as an attractive approach in the field of organic synthesis to introduce chemical functionality into organic molecules because of its environmentally benign and practical nature . Synthetic electrochemistry could achieve redox reactions without needing transition-metal catalysts or toxic reagents due to the use of electrons as oxidizing or reducing reagents . In 2019, our research group reported an environment-friendly and efficient electrochemical fluoroalkylation/cyclization of N -aryacryamide to access fluorinated oxindoles and quinolinones with wide functional groups (Scheme c) .…”