Novel synthetic approach for the preparation of mono- and bis-aminoboranes and their initial reactivity studies

We wish to report a new approach, based on controlled hydroboration of imines, for synthesising mono- and acyclic bis-aminoboranes. This was made possible by the formation and isolation of imine-BH3 adducts, which represented a crucial step for the overall synthetic method. These adducts were then converted to mono-aminoboranes via a 1,3-hydride shift which most likely occurred intermolecularly. Further reaction of mono-aminoboranes with imines yielded a variety of acyclic (a)symmetric bis-aminoboranes. Additionally, the reduction of carbonyl groups such as aldehydes by mono-aminoboranes was established to be mainly due to the potential hydride activity of these compounds via the formation of “four-coordinate boranes” Lastly, deoxygenating coupling was observed when hydroboration of carbonyl compounds, including CO2, was carried out using bis-aminoboranes.