2,3-Dichloropropene → 5-Bromo-2-methyl-1-benzothiophene

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Reaction Steps

4-Bromobenzenethiol (10.0 g, 52.8 mmol) was dissolved in acetone (100 ml), and anhydrous potassium carbonate (8.8 g, 63 mmol), and 2,3-dichloropropene (7.0 g, 63 mmol) were added. The mixture was stirred at room temperature for 14 hr. Acetone was distilled away under reduced pressure and toluene and water were added to the residue. The toluene layer was separated. The organic layer was washed with water, and dried over anhydrous sodium sulfate. The desiccant was filtered away and the filtrate was concentrated under reduced pressure to give a pale-yellow oil (13.9 g). This oil was dissolved in diethyl aniline (45 ml), and the mixture was stirred at 205° C. for 50 hr with heating. Diethyl aniline was distilled away under reduced pressure, and 3N hydrochloric acid and toluene were added to the residue. After the toluene layer was separated, the organic layer was dried over anhydrous sodium sulfate. The desiccant was filtered off, and the filtrate was concentrated under reduced pressure. The residual crystalline oil was dissolved in hexane, and the insoluble oil was removed by decantation. After concentration under reduced pressure, the residue was recrystallized from a small amount of hot hexane to give the objective compound (5.9 g, 58%) as colorless crystals.

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