A solution of DMSO (0.25 mL, 3.5 mmol) in CH2Cl2 (10 mL) at −78 C was treated with a solution of oxallyl chloride (2N in CH2Cl2, 0.8 mL, 1.6 mmol) dropwise. After stirring for 15 min, a solution of 9-(2-hydroxy-4-phenyl-butyl)-2-pyridin-4-yl-3-(3-trifluoromethyl-phenyl)-6,7,8,9-tetrahydro-pyrimido[1,2-a]pyrimidin-4-one (227 mg, 0.43 mmol) in CH2Cl2 (15 mL) was added. The mixture was stirred at −60 C for 15 min before a solution of Et3N (0.5 mL, 3.6 mmol) in CH2Cl2 (3 mL) was added. The reaction mixture was allowed to warm to room temperature overnight and was washed with NaHCO3 (aq). The organic layer was dired (Na2SO4), and concentrated. The residue was eluted on silica gel with 0-5% (2N NH3-MeOH in CH2Cl2) to afford the product as a light yellow solid (148 mg, 63%). M+1 519.
