Sodium Cyanoborohydride [Reducing Agent]

Typical Procedure:
To a stirred solution of N-ethylbenzylamine (675 mg, 5 mmol) and 37% aqueous formaldehyde (2 mL, 25 mmol) in acetonitrile (15 mL) is added sodium cyanoborohydride (500 mg, 8 mmol). A vigorous exothermic reaction ensues, and a dark residue separates. The reaction mixture is stirred for 15 min, and then glacial acetic acid is added dropwise until the solution tests neutral on wet pH paper. Stirring is continued for an additional 45 min, glacial acetic acid being added occasionally to maintain the pH near neutrality. The solvent is evaporated at reduced pressure, and 2 N KOH (20 mL) is added to the residue. The resulting mixture is extracted with ether (3 × 20 mL). The combined ether extracts are washed with 0.5 N KOH (20 mL) and then extracted with 1 N HCl (3 × 10 mL). The acid extracts are combined and neutralized with solid KOH and then extracted with ether (3 × 20 mL). The combined ether extracts are dried (K₂CO₃) and evaporated in vacuo to give N-methyl-N-ethylbenzylamine (735 mg, Y. 98%) as a colorless, GPLC-pure oil.