Theoretical description for the Rh(I)-catalyzed borylation mechanism of a typical aryl cyanide

• DFT calculations elucidate the mechanism details of the Rh-catalytic borylation reaction.
• The iminoacyl species is more favorable than the iminylrhodium species.
• The catalytically active species is the Rh–B complex rather than the Rh–Cl one.
• Molecular structures of iminoacyl and boryl isocyanide species are established.

A recent experimental study by Tobisu et al. (J. Am. Chem. Soc. 2012, 134, 115–118.) reported a new type of catalytic borylation reactions, the Rh-catalytic reaction of aryl cyanides with diboron to afford arylboronic acids. To better understand the borylation mechanism at the molecular level, this work provides a theoretical description for the elementary steps of the reaction of a typical aryl cyanide with diboron in the presence of a rhodium catalyst [RhCl(cod)]2 with the aid of DFT calculations. It is found that i) the catalytically active species is the Rh–B complex rather than the Rh–Cl one, ii) the Rh–Ar intermediate is formed through the iminoacyl species rather than the iminylrhodium species previously proposed by Tobisu et al., and iii) the structures of iminoacyl and boryl isocyanide species are also disagreement with those experimental studied by Tobisu et al. Calculated results show a clear mechanistic picture of the catalytic borylation reaction of the aryl cyanide.

DFT calculations show the [RhCl(cod)]2 catalyzed borylation mechanism of a typical aryl cyanide using diboron reagent.Figure optionsDownload as PowerPoint slide