[Br:1][C:2]1[CH:3]=[C:4]([CH:7]=[CH:8][C:9]=1[OH:10])[CH:5]=[O:6].C(=O)([O-])[O-].[Cs+].[Cs+].Br[CH2:18][C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20]>CN(C=O)C>[Br:1][C:2]1[CH:3]=[C:4]([CH:5]=[O:6])[CH:7]=[CH:8][C:9]=1[O:10][CH2:18][C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20]To a solution of 3-bromo-4-hydroxybenzaldehyde (5 g, 25 mmol, 1 eq, Aldrich, Milwaukee, Wis., USA) in DMF (200 mL) was added solid cesium carbonate (16.25 g, 50 mmol, 2 eq) followed by dropwise addition of t-butyl 2-bromoacetate (4.4 mL, 30 mmol, 1.2 eq, Aldrich, Milwaukee, Wis., USA). After stirring at room temperature for 18 h, the DMF was removed in vacuo and the resultant residue was extracted between EtOAc (50 mL) and brine (50 mL). The separated organic layer was dried (Na2SO4), and concentrated in vacuo to give 7.74 g (98.4%) of t-butyl 2-(2-bromo-4-formylphenoxy)acetate (1). 1HNMR (CDCl3, 300 MHz): δ 9.83 (s, 1H), 8.08 (d, 1H), 7.76 (dd, 1H), 6.83 (d, 1H), 4.67 (s, 1H).1.44 (s, 9H).
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