title: Electrophilic Aromatic Substitution with Silicon Electrophiles: Catalytic Friedel-Crafts C-H Silylation.
abstract: Electrophilic aromatic substitution is a fundamental reaction in synthetic chemistry. It converts C-H bonds of sufficiently nucleophilic arenes into C-X and C-C bonds using either stoichiometrically added or catalytically generated electrophiles. These reactions proceed through Wheland complexes, cationic intermediates that rearomatize by proton release. Hence, these high-energy intermediates are nothing but protonated arenes and as such strong Brønsted acids. The formation of protons is an issue in those rare cases where the electrophilic aromatic substitution is reversible. This situation arises in the electrophilic silylation of C-H bonds as the energy of the intermediate Wheland complex is lowered by the β-silicon effect. As a consequence, protonation of the silylated arene is facile, and the reverse reaction usually occurs to afford the desilylated arene. Several new approaches to overcome this inherent challenge of C-H silylation by SEAr were recently disclosed, and this Minireview summarizes this progress.
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany.
authors.forename: Susanne
authors.identifier: 0000-0001-5113-7646
authors.initials: S
authors.lastname: Bähr
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany.
authors.forename: Martin
authors.identifier: 0000-0002-1487-9218
authors.initials: M
authors.lastname: Oestreich
keywords: C−H functionalization; Si−H activation; cations; electrophilic aromatic substitution; homogeneous catalysis