Homoallyl bromide → Diethyl 2-(but-3-enyl)-2-(tert-butoxycarbonylamino)malonate

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To a suspension of sodium hydride (8.7 g, 218 mmol, 60% suspension) in dimethylformaamide (250 mL) at 0° C. was added diethyl 2-(tert-butoxycarbonylamino)malonate (50.0 g, 182 mmol) in dimethylformaamide (250 mL). After stirring for 30 minutes, 4-bromobut-1-ene (29.5 g, 218 mmol, 22.2 mL) was added and the mixture was warmed to 90° C. After stirring an additional 4 h, the solution was cooled to room temperature and the solvents were removed by evaporation. The resulting residue was diluted with ethyl acetate (1.0 L), washed successively with water (2×250 mL), saturated aqueous sodium chloride (1×200 mL) and concentrated. Purification using a combiflash system (330 g silica column, eluted with 15-50% ethyl acetate in heptanes) gave diethyl 2-(but-3-enyl)-2-(tert-butoxycarbonylamino)malonate (54 g, 90%). 1H NMR (CDCl3) δ 5.92 (bs, 1H), 5.79-5.71 (m, 1H), 5.03-4.93 (m, 2H), 4.24-4.19 (m, 4H), 2.36 (m, 2H), 1.96-1.93 (m, 2H), 1.42 (s, 9H), 1.27-1.24 (m, 6H).

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