[CH3:1][C:2]1[C:11]([Br:12])=[CH:10][C:9]([CH3:13])=[C:8]2[C:3]=1[C:4](=[O:14])[CH2:5][CH2:6][S:7]2.[Cl-].[Na+].[BH4-].[Na+].Cl>ClCCl.CO>[CH3:1][C:2]1[C:11]([Br:12])=[CH:10][C:9]([CH3:13])=[C:8]2[C:3]=1[CH:4]([OH:14])[CH2:5][CH2:6][S:7]2
100 ml of methanol and 30 ml of dichloromethane were added to 10 g (36.9 mmol) of 5,8-dimehyl-6-bromothiochroman-4-one. While the mixture was maintained at a temperature not exceeding 0° C. with a sodium chloride aqueous solution and an ice bath, 0.70 g (18.4 mmol) of sodium borohydride as a reducing agent was gradually added. The mixture was allowed to react at room temperature for 3 hours, and then the reaction mixture was poured into a 5% hydrochloric acid aqueous solution and extracted with dichloromethane. The resultant dichloromethane layer was dried over anhydrous sodium sulfate and concentrated to give 9.2 g (yield 91%) of 5,8-dimethyl-4-hydroxy-6-bromothiochroman (corresponding to compound of the formula (VI)).
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