Amine–borane dehydrogenation chemistry: Metal-free hydrogen transfer, new catalysts and mechanisms, and the synthesis of polyaminoboranes

Over the past decade it has been shown that amine–boranes RR′R″N·BH3 (R, R′, R″ = H, alkyl, aryl) undergo efficient catalytic dehydrocoupling/dehydrogenation using transition metal or main group precatalysts to produce various classes of products including aminoboranes, borazanes, borazines, and, most recently, the first examples of soluble high molecular weight polyaminoboranes. Furthermore, related studies have also demonstrated that amine–boranes can act as hydrogen sources in metal-catalyzed or metal-free transfer hydrogenation reactions of unsaturated organic species, including imines and polar olefins. Our group has shown that metal-free hydrogen exchange reactions are also possible between amine–boranes and aminoboranes under mild conditions. This review provides an overview of our recent work in each of these areas.