Br[CH2:2][C:3]1[C:4]([F:13])=[C:5]([CH:10]=[CH:11][CH:12]=1)[C:6]([O:8][CH3:9])=[O:7].C(=O)(O)[O-:15].[Na+].CS(C)=O>C(OCC)(=O)C>[F:13][C:4]1[C:3]([CH:2]=[O:15])=[CH:12][CH:11]=[CH:10][C:5]=1[C:6]([O:8][CH3:9])=[O:7]Dimethylsulfoxide was degassed with argon for 1 h. Methyl 3-(bromomethyl)-2-fluorobenzoate (3.6 g, 14.5 mmol) from Step B above and solid sodium bicarbonate (10.5 g, 124.6 mmol) were added to the DMSO and the mixture was heated at 115° C. for 2 h. The reaction mixture was then diluted with ethyl acetate, washed with brine, dried (Na2SO4), filtered, concentrated under reduced pressure and purified by column chromatography (silica gel, 0% to 2% ethyl acetate in hexanes) to give methyl 2-fluoro-3-formylbenzoate (1.8 g, 67%): 1H NMR (500 MHz, CDCl3) δ 10.43 (s, 1H), 8.22-8.19 (m, 1H), 8.09-8.06 (m, 1H), 7.37-7.34 (m, 1H), 3.98 (s, 3H).
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