Interrogating Redox and Lewis Base Activations of Aminoboranes

Since their discovery, aminoboranes (R2N-BR2) have been applied as intermediates in chemical hydrogen storage devices, asymmetric catalysts, semi-conductors, and amination/borylation reagents. Recently, chemists have extended their application to reagents for difunctionalization reactions, wherein the N-B bond is cleaved and the amine and boronic ester fragments are distributed across an organic molecule. Generally, harsh conditions or loss of the borane/amine fragment as waste is required to enable reactivity of the enthalpically stable partial sp2-hybridized N-B bond. We sought to show that mild avenues also exist to disrupt the dative N-B pi-bond . Herein, we survey the coordinative capabilities of neutral Lewis bases to (amino)-pinacolboranes and whether the partial sp2-hybridized N-B bond can be oxidized electro-or photochemically in analogous fashion to C=C bonds. The results of these studies are strongly in the affirmative and should guide the thought processes of organic chemists when designing new reactions using aminoboranes.