Scalable, Green Synthesis of Heteroaromatic Amine-boranes

In situ generated, transient sodium monohydroxyborohydride readily reacts with a present amine to form amine-borane adducts in ethyl acetate at room temperature. Synthesis of heteroaromatic pyridine-, 2-picoline-, and 5-ethyl-2-methylpyridine-boranes, those relevant large-scale reductive aminations, has been demonstrated 100 mmol scale, pyridine-borane 1.1 mole scale. This first report substituting for tetrahydrofuran, the traditional solvent synthesis, allows activation borohydride by aqueous portion heterogeneous dual-solvent system. These factors make this green protocol more economical than currently available production amine-boranes as demonstrated, quantitatively, computed chemistry metrics.