To a solution of [9-chloro-1-(2-chloro-4-methoxyphenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl](cyclopropyl)methanol (120 mg, 0.26 mmol), 1,1′-(azodicarbonyl)dipiperdine (131 mg, 0.52 mmol) in tetrahydrofuran (5.0 mL) was added tri(n-butyl)phosphine (0.130 mL, 0.52 mmol) at room temperature. After the mixture was stirred at room temperature for 10 min under nitrogen atmosphere, 2,2-difluoroethanol (0.165 mL, 2.61 mmol) was added to the reaction mixture. The mixture was stirred at 50° C. for 16 hr under nitrogen atmosphere. The mixture was concentrated in vacuo and diethyl ether was added to the residue. The solid was removed by filtration and the filtrate was concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with a 10-50% ethyl acetate/n-hexane gradient mixture and recrystallization from ethyl acetate/n-hexane to give the title compound (72.8 mg, 0.155 mmol, 58%) as colorless crystals.
