Cooperative catalytic activation of Si-H bonds by a polar Ru-S bond: Regioselective low-temperature c-h silylation of indoles under neutral conditions by a Friedel-crafts mechanism

Klare HFT, Oestreich M, Ito J, Nishiyama H, Ohki Y, Tatsumi K

Abstract

Merging cooperative Si-H bond activation and electrophilic aromatic substitution paves the way for C-3-selective indole C-H functionalization under electronic and not conventional steric control. The Si-H bond is heterolytically split by the Ru-S bond of a coordinatively unsaturated cationic ruthenium(II) complex, forming a sulfur-stabilized silicon electrophile. The Wheland intermediate of the subsequent Friedel-Crafts-type process is assumed to be deprotonated by the sulfur atom, no added base required. The overall catalysis proceeds without solvent at low temperature, only liberating dihydrogen.