To stirred solution of 3-(benzyloxy)-N′-(2-(4-fluorophenyl)acetyl)-9,9-dimethyl-4-oxo-4,6,7,9-tetrahydropyrimido[2,1-c][1,4]oxazine-2-carbohydrazide (0.075 g, 0.16 mmol), Ph3P (0.074 g, 0.28 mmol) and DIEA (0.16 mL, 0.91 mmol) in anhydrous CH3CN (3 mL) was added hexachloroethane (0.048 g, 0.20 mmol) all at once at room temperature. After 4 h, the resulting greenish-yellow reaction mixture was purified by preparative HPLC on a C18 column using water/MeOH containing 0.1% TFA as eluent to afford title compound (0.072 g, 86% yield) as a yellow solid. 1HNMR (500 MHz, CDCl3) δ: 7.42-7.40 (2H, m), 7.30-7.28 (3H, m), 7.24 (2H, dd, J=8.2, 5.55.34 (2H, s), 4.20 (2H, s), 4.07-4.01 (4H, m), 1.64 (6H, s). Hz)), 6.99 (2H, t, J=8.6 Hz), HRMS (M+H) calcd for C25H24N4O4F: 463.1782. found: 463.1788.
