Mechanistic insights into the transmetalation step of a Suzuki–Miyaura reaction of 2(4)-bromopyridines: characterization of an intermediate

The mechanistic study of the palladium-catalyzed Suzuki–Miyaura cross-coupling between bromophenylpyridine compounds and phenylboronic acid led to the NMR identification of a transient intermediate in the transmetalation step. This species was identified by DFT calculations as a [Pd{Ph-B(OH)3−}{C5H2RN}(PR3)2] complex, containing a boronate ligand coordinated through an oxygen group to the metal center. The fitting of this intermediate within recent mechanistic proposals on the mechanism of transmetalation is discussed.