Sodium hydride → Methyl (2-oxo-1,3-oxazinan-3-yl)acetate

A solution of 0.20 g (2.0 mmol) of 1,3-oxazinan-2-one from step A in 2 mL of anhydrous DMF was added to a 10 mL round bottom flask containing 0.13 g (3.2 mmol) of a 60% sodium hydride suspension in mineral oil under an atmosphere of nitrogen. After stirring for 10 min 0.37 g (2.4 mmol) of methyl brornoacetate was added in one portion and the reaction mixture was allowed to stir overnight. The reaction mixture was then quenched with 5 mL of a saturated aqueous ammonium chloride solution and then diluted with 20 mL of water. The resulting suspension was extracted with ethyl acetate (3×10 mL) and the combined organics were washed with water (2×3 mL), brine (1×3 mL) and dried over magnesium sulfate. The mixture was filtered, evaporated and purified by silica gel chromatography eluting with a 5% methanol in ethyl acetate mixture to afford the title compound as a clear oil (0.068 g, 20%). 1HNMR (500 MHz, CDCl3) δ: 4.28 (t, J=5.4 Hz, 2H), 4.03 (s, 2H), 3.70 (s, 3H), 3.36 (t, J=6.2 Hz, 2H), 2.08-2.04 (m, 2H). LC-MS: m/z (ES) 174 (MH)+.