A mixture of [1-(3,5-dichloro-benzyl)-1H-imidazol-2-ylmethyl]-(3-fluoro-benzyl)-amine, (200 mg, 0.55 mmol), acetone (81 uL, 1.10 mmol) and 3A molecular sieves (300 mg) in MeOH (3 mL) was stirred at ambient temperature under N2. After 5 h, NaBH3CN was added and the mixture stirred for an additional 2 h. Water (2 mL) was added and the reaction mixture concentrated in vacuo. The residue was taken up in 1N NaOH (20 mL) and extracted with CH2Cl2 (3×30 mL). The combined extracts were dried over Na2SO4 and concentrated in vacuo. The crude material was purified by chromatography (silica gel, 100% EtOAc) and the isolated product converted to the di-hydrochloride salt by treatment with excess anhydrous HCl in methanol solution. The volatiles were removed in vacuo to afford the desired product 6a (58 mg, 26%) as an off-white solid: ESI MS m/z 406 [C21H22Cl2FN3+H]+.
