Catalytic generation of borenium ions by cooperative B-H bond activation: the elusive direct electrophilic borylation of nitrogen heterocycles with pinacolborane

Timo Stahl; Kristine Müther; Yasuhiro Ohki; Kazuyuki Tatsumi; Martin Oestreich

doi:10.1021/ja405925w

Catalytic generation of borenium ions by cooperative B-H bond activation: the elusive direct electrophilic borylation of nitrogen heterocycles with pinacolborane

J Am Chem Soc. 2013 Jul 31;135(30):10978-81. doi: 10.1021/ja405925w. Epub 2013 Jul 17.

Authors

Timo Stahl¹, Kristine Müther, Yasuhiro Ohki, Kazuyuki Tatsumi, Martin Oestreich

Affiliation

¹ Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany.

PMID: 23855894
DOI: 10.1021/ja405925w

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.