The Transmetalation Process in Suzuki-Miyaura Reactions: Calculations Indicate Lower Barrier via Boronate Intermediate

Recent experimental reports have called into question the validity of the boronate mechanism (through a R-B(OH3- intermediate) for the transmetalation step in the Suzuki-Miyaura cross-coupling, favoring instead the palladium hydroxo pathway (through an [LnPd(R′)(OH)] intermediate). Herein we report DFT calculations with the M06 functional performed on realistic model systems, including a combination of explicit solvent molecules along with a continuum method. These computational results support the boronate mechanism. The mechanistic proposal is shown to be compatible with the available experimental evidence.