Premium
Electrophilic Aromatic Substitution with Silicon Electrophiles: Catalytic Friedel–Crafts C−H Silylation
Author(s) -
Bähr Susanne,
Oestreich Martin
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201608470
Subject(s) - electrophile , protonation , silylation , chemistry , electrophilic aromatic substitution , electrophilic substitution , substitution reaction , carbocation , friedel–crafts reaction , nucleophile , nucleophilic aromatic substitution , cationic polymerization , medicinal chemistry , catalysis , nucleophilic substitution , organic chemistry , ion
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 S E Ar were recently disclosed, and this Minireview summarizes this progress.