To a solution of 1-[9-chloro-1-(6-methoxy-2-methylpyridin-3-yl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]propan-1-ol (120.0 mg, 0.310 mmol) in tetrahydrofuran (3.0 mL) was added 1,1′-(azodicarbonyl)dipiperidine (156.4 mg, 0.620 mmol) and tributylphosphine (154.5 μL, 0.620 mmol). After 10 min, to the mixture was added 2,2,2-trifluoroethanol (225.9 μL, 3.100 mmol). The reaction mixture was stirred at 60° C. for 5 hrs. The mixture was concentrated. To the residue was added diethyl ether and the precipitate was removed by filtration. The residue was purified by silica gel column chromatography eluting with a 0-40% ethyl acetate/n-hexane gradient mixture. The resulting solid was recrystallized from diisopropyl ether/n-hexane to give the title compound as a colorless powder (56.5 mg, 0.120 mmol, 39).
