Catalytic Approach to Diverse α-Aminoboronic Acid Derivatives by Iridium-Catalyzed Hydrogenation of Trifluoroborate-Iminiums

A series of structurally diverse benzyl protected trifluoroborate-ammoniums were prepared in good to high yields by an efficient hydrogenation of corresponding trifluoroborate-iminiums using Crabtree's catalyst. Subsequent N- and B-deprotections were demonstrated on selected examples to provide several alpha-aminoboronic acids. Preliminary experiments on asymmetric version of the reaction indicated a correlation between E/Z-ratio in the trifluoroborate-iminium substrate and enantioselectivity. The broad scope, operational simplicity and efficiency of the presented method imply its high potential for a facile access to libraries of alpha-aminoboronic acid derivatives that can be used in medicinal chemistry applications and beyond.

Automated summary

A series of structurally diverse benzyl protected trifluoroborate-ammoniums were efficiently prepared by hydrogenation of corresponding trifluoroborate-iminiums using Crabtree's catalyst, with subsequent deprotections yielding alpha-aminoboronic acids. Initial experiments on asymmetric reactions showed a correlation between E/Z-ratio in the substrate and enantioselectivity, highlighting the potential of this method for accessing libraries of alpha-aminoboronic acid derivatives for medicinal chemistry applications and beyond.