Aminoboration of Directing-Group-Free Alkenes with R2N–H

Aminoboration of Directing-Group-Free Alkenes with R2N–H

Author: ChemistryViews

Aminoboration of simple alkenes with nitrogen nucleophiles is challenging. Catalytic conversion with palladium (aminopalladation followed by transmetalation with a diboron reagent) is difficult. The alkylpalladium(II) intermediate is unstable and rapidly tends to fall apart upon β-hydride elimination.

Kami L. Hull, University of Texas at Austin, USA, and colleagues have developed a palladium/iron co-catalyzed aminoboration to realize the directing-group-free aminoboration of terminal alkenes and norbornenes with common nitrogen nucleophiles and Bis(pinacolato)diboron (B2pin2). In their reaction, the transient alkylpalladium(II) undergos intermolecular transmetalation faster than intramolecular β-hydride elimination.

The iron cocatalyst is critical for achieving the desired reactivity. As a halophilic Lewis acid, it serves to release the transmetallation-active cationic alkylpalladium intermediate. In addition, it serves as a redox shuttle in the regeneration of the Pd(II) catalyst by reactivation of the nanoparticulate palladium.



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