title: Catalytic generation of borenium ions by cooperative B-H bond activation: the elusive direct electrophilic borylation of nitrogen heterocycles with pinacolborane.
abstract: The B-H bond of typical boranes is heterolytically split by the polar Ru-S bond of a tethered ruthenium(II) thiolate complex, affording a ruthenium(II) hydride and borenium ions with a dative interaction with the sulfur atom. These stable adducts were spectroscopically characterized, and in one case, the B-H bond activation step was crystallographically verified, a snapshot of the σ-bond metathesis. The borenium ions derived from 9-borabicyclo[3.3.1]nonane dimer [(9-BBN)2], pinacolborane (pinBH), and catecholborane (catBH) allowed for electrophilic aromatic substitution of indoles. The unprecedented electrophilic borylation with the pinB cation was further elaborated for various nitrogen heterocycles.
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Stahl
authors.forename: Kristine
authors.initials: K
authors.lastname: Müther
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ohki
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tatsumi
authors.forename: Martin
authors.initials: M
authors.lastname: Oestreich