4-Fluoro-6-methyl-1-[1-(tetrahydro-2H-pyran-4-yl)-4-piperidinyl]-1,3-dihydro-2H-benzimidazol-2-one free base (1.499 mmol, 500 mg, 1 wt) was weighed into a 250 ml round bottomed flask, acetonitrile (95 vol., 47.5 ml) and n-propanol (80 vol., 40 ml) were added, giving a white slurry. Methanesulfonic acid (1 eq, 1.499 mmol, 97 □l) was pipetted into the flask. The contents of the flask were heated using a hot air gun—the slurry dissolved and a white precipitate formed. The precipitate was magnetically stirred at 35° C. for four days under nitrogen. After cooling to ambient temperature, the solid was isolated by vacuum filtration and washed with acetonitrile (10 vol. 5 ml). The white solid was dried under high vacuum at 60° C. for 25 hours. 561 mg, 87%, white solid.
