[Br:1][C:2]1[CH:7]=[CH:6][C:5]([S:8][CH2:9][C:10]([OH:12])=O)=[CH:4][CH:3]=1.S(Cl)(Cl)=O.[Cl-].[Al+3].[Cl-].[Cl-].Cl>O.ClCCl.CN(C)C=O>[Br:1][C:2]1[CH:7]=[CH:6][C:5]2[S:8][CH2:9][CH:10]([OH:12])[C:4]=2[CH:3]=1
To dichloromethane (750 mL) suspension of 250 g of (4-bromophenylthio)acetic acid were added 2.5 mL of N,N-dimethylformamide and 132 g of thionyl chloride, which was then refluxed for 1 hour. After cooling the reaction mixture to 20° C., thereto was dropwise added dichloromethane (1500 mL) suspension of 148 g of aluminum chloride at 5 to 15° C., which was then stirred at 15 to 25° C. for 1.5 hours. Next, this reaction mixture was added dropwise to a mixed solution of 1310 mL of water and 188 mL of hydrochloric acid under cooling. The organic layer was separated, thereto was added 1250 mL of water, and the pH was adjusted to 3.0 with 5% potassium carbonate aqueous solution. The organic layer was separated and cooled to 5° C. Thereto were added 15.3 g of sodium borohydride and 500 mL of methanol, which was then stirred at 10 to 20° C. for 2 hours. To the reaction solution was added 750 mL of water, followed by adjustment to pH7.0 using acetic acid and left unattended in room temperature overnight. To the reaction solution was added 200 mL of 5% potassium hydroxide aqueous solution, and the organic layer was separated. To the organic layer was 25.0 g of activated carbon, which was then stirred at room temperature. Insoluble matter was filtered off, and the solvent of filtrate was distilled off. To the resultant residue was added cyclohexane, the crystals precipitated were collected by filtration to provide 194 g of 5-bromo-2,3-dihydro-1-benzothiophen-3-ol as pale red solid form.
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