Yield:54260-84-3 43%

Reaction Conditions:

with bromine in diethyl ether at 0; for 3 h;

Steps:

7.A Step A: ethyl 3-bromo-4-oxopentanoate

To a solution of ethyl 4-oxopentanoate (4.92 mL, 34.7 mmol) in Et₂O (180 mL) at about 0° C. was added bromine (1.8 mL, 34.7 mmol) in Et₂O (10 mL) and the reaction was stirred for about 3 h. To the reaction mixture was added saturated aqueous sodium thiosulfate (50 mL) and stirred for about 10 min. The reaction was warmed to ambient temperature. The organic layer was separated and the aqueous layer was back extracted with Et₂O (30 mL). The combined organic layers were washed with water (20 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The resulting oil was purified by column chromatography (SiO₂, EtOAc/heptane 100:0 to 0:20) to afford ethyl 3-bromo-4-oxopentanoate (3.29 g, 14.6 mmol, 43%). ¹H NMR (CDCl₃) δ 4.67-4.33 (m, 1H), 4.15 (q, J=7.1 Hz, 2H), 3.29-3.22 (m, 1H), 2.90-2.86 (m, 1H), 2.42 (s, 3H), 1.26 (t, J=7.1 Hz, 3H).

References:

US2014/179676,2014,A1 Location in patent:Paragraph 0961