Improving Carbene–Copper-Catalyzed Asymmetric Synthesis of α-Aminoboronic Esters Using Benzimidazole-Based Precursors

By using a benzimidazole core and N-substitutions to tune the electronic properties of the corresponding N-heterocyclic carbenes, a one-pot protocol for efficient synthesis of α-aminoboronic esters without the need of a glovebox was developed in this work. The starting materials for the transformation can also be extended from aldehydes to ketones. An alternative protocol with short reaction time using preformed carbene-copper chloride is also described.