Palladium-Catalysed Cross-Coupling of Benzylammonium Salts with Boronic Acids under Mild ConditionsWe are grateful to the Engineering and Physical Sciences Research Council (EPSRC, Grant Number EP/N005422/1) and Pfizer for a CASE studentship (H.J.D.), the EPSRC and the Royal Society for a University Research Fellowship (R.J.P.). P.L.T. thanks the Swiss-European Mobility Programme for Traineeships for funding his stay in Cambridge.
Received: 15 June 2017
Accepted after revision: 20 July 2017
23 August 2017 (eFirst)
Published as part of the Bürgenstock Special Section 2017 Future Stars in Organic Chemistry
Herein, we give a full account of the development of the palladium-catalysed cross-coupling of benzylammonium salts with boronic acids. A range of benzylamine-derived quaternary ammonium salts can be coupled with boronic acids under relatively mild conditions. Our optimization has identified ligands that can be used to chemoselectively cross-couple at the ammonium in the presence of chlorides. We demonstrate that intramolecular palladium-catalysed C–H activation is also a viable pathway for the putative benzyl-Pd(II) intermediate obtained upon oxidative addition and have optimised this to obtain fluorene in good yield.