[CH2:1]([C:8]1[C:12]2[CH:13]=[C:14]([CH3:18])[CH:15]=[C:16]([Br:17])[C:11]=2[O:10][CH:9]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.P(Cl)(Cl)(Cl)=O.[OH-].[Na+].CN([CH:29]=[O:30])C>>[CH2:1]([C:8]1[C:12]2[CH:13]=[C:14]([CH3:18])[CH:15]=[C:16]([Br:17])[C:11]=2[O:10][C:9]=1[CH:29]=[O:30])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=13-Benzyl-7-bromo-5-methyl-benzofuran (3.93 g, 13.05 mmol) was mixed with 10 ml DMF. Phosphorus oxychloride (1.8 ml, 19.3 mmol) was added and the reaction mixture was heated to 50° C. for 16 hours. Additional phosphorus oxychloride (3.6 ml, 38.6 mmol) was added and the reaction mixture was heated to 90° C. for an hour, then to 100° C. for five hours. The mixture was cooled to room temperature, poured onto ice and aqueous sodium hydroxide was added until the mixture reached pH=3. The mixture was extracted with ethyl acetate, dried over magnesium sulfate, filtered, and absorbed onto 20 gm silica gel. The silica gel was layered over 100 gm silica gel in a fritted funnel and eluted with five portions of 400 ml hexanes (to give 0.33 g recovered starting material) and two portions of 400 ml of 10/90 ethyl acetate/hexane to give 3-benzyl-7-bromo-5-methyl-benzofuran-2-carbaldehyde (2.61 g, 61% yield). MS: (M+H)+ 330.
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