[CH3:1][O:2][C:3]([C:5]12[CH2:12][CH2:11][C:8](C(O)=O)([CH2:9][CH2:10]1)[CH2:7][CH2:6]2)=[O:4].[OH-].[Na+].[Br:18]Br>CC(C)=O.O.CCCCCC.[N+]([O-])([O-])=O.[Ag+].COC(C12CCC(C(O[Ag])=O)(CC1)CC2)=O>[Br:18][C:8]12[CH2:11][CH2:12][C:5]([C:3]([O:2][CH3:1])=[O:4])([CH2:10][CH2:9]1)[CH2:6][CH2:7]2
To a suspension of 4-(methoxycarbonyl)bicyclo[2.2.2]octane-1-carboxylic acid (11.0 g, 51.8 mmol) in acetone (80 mL) was added aqueous sodium hydroxide solution (1 M, 51.8 mL, 51.8 mmol) and a solution of silver nitrate (8.8 g, 51.9 mol) in water (10 mL). The precipitate formed was collected by filtration, washed with water, acetone and diethyl ether and dried in vacuo at 115° C. for 4 h. The obtained ((4-(methoxycarbonyl)-bicyclo[2.2.2]octane-1-carbonyl)oxy)silver (15.3 g, 47.9 mmol) was suspended in hexane (125 mL), followed by addition of bromine (7.7 g, 48.1 mmol) over 30 min at room temperature. After the addition was completed, the reaction mixture was stirred at room temperature for another 30 min. The reaction mixture was filtered to remove the solid, and the filter cake was washed with hexane (150 mL×4). The combined organic filtrates were washed with saturated aqueous sodium bicarbonate solution (150 mL×2) and brine (200 mL), then dried over magnesium sulfate. Concentration under reduced pressure gave the crude product, which was purified by silica gel column chromatography (5% ethyl acetate in petroleum ether) to afford the title compound (4.2 g, 0.17 mol, 33% yield over two steps). 1H NMR (400 MHz, CDCl3): δ ppm 3.64 (s, 3H), 2.27-2.20 (m, 6H), 1.98-1.94 (m. 6H).
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