Synlett 2017; 28(09): 1011-1017
DOI: 10.1055/s-0036-1588709
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© Georg Thieme Verlag Stuttgart · New York

Ion-Pair-Directed meta-Selective C–H Borylation of Aromatic Quaternary Ammonium Salts

Madalina T. Mihai, Robert J. Phipps*
  • Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK   Email: rjp71@cam.ac.uk
Further Information

Publication History

Received: 06 December 2016

Accepted after revision: 23 January 2017

Publication Date:
13 February 2017 (eFirst)

Abstract

We recently reported the use of ion pairing as a key noncovalent interaction to control regioselectivity in the iridium-catalyzed C–H borylation of aromatic quaternary ammonium salts. Two classes of substrates, benzylamine- and aniline-derived ammonium salts were selectively borylated at the meta position by employing a newly developed anionic ligand for the iridium. It was proposed that the ligand interacts with the cationic substrate via an ion-pairing interaction, positioning the substrate in the optimal orientation for selective activation of the meta C–H bond.

1 Introduction

2 Ion-Pair-Directed meta C–H Borylation

3 Control Experiments

4 Unexpected Selectivity with dtbpy in Cyclohexane

5 Conclusions