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Magnesium turnings (0.24 g) were placed in a two-neck 100 mL round-bottom flask fitted with a reflux condenser and a magnetic stir bar. The whole apparatus was flame-dried and allowed to cool to ambient temperature. Dry THF (17 mL) and a small crystal of iodine were then introduced followed by slow addition of 4-bromophenyl triisopropylsilyl ether (3.5 g) while stirring at ambient temperature. The reaction mixture was warmed to a gentle reflux for 1 h or until the magnesium turnings were completely consumed to give a 0.5 M solution of the Grignard reagent. This freshly prepared Grignard solution (15 mL) was added slowly to a stirring solution of 6-benzyloxy-2-(dimethylamino)benzo[b]thiophen-3-yl 3-methoxy-4-[(1-pyrrolidinyl)methyl]phenyl ketone (2.5 g, 5.0 mmol) in THF (15.0 mL) at 0° C. under argon. The mixture was stirred at 0° C. for 2 h before quenching with saturated aqueous NH4Cl solution (50 mL) and extraction with CH2Cl2 (50 mL×3). The combined organic layers were dried with sodium sulfate and concentrated under reduced pressure. Chromatography with EtOAc afforded a oily brown material as the major fraction. This material was dissolved in THF (25 mL), treated with a solution of tetrabutylammonium fluoride (1.0 M in THF, 6 mL) at ambient temperature for 1 h, and then concentrated under reduced pressure. Chromatography with Et3N:MeOH:EtOAc (5:10:85) afforded the title compound as a yellow foam (2.75 g, 100%).

1. custombefore quenching with saturated aqueous NH4Cl solution (50 mL) and extraction with CH2Cl2 (50 mL×3)
2. dry with materialThe combined organic layers were dried with sodium sulfate
3. concentrationconcentrated under reduced pressure
4. customChromatography with EtOAc afforded a oily brown material as the major fraction
5. concentrationconcentrated under reduced pressure