Hydrochloric Acid → 8-fluoro-3-(4-fluorophenyl)-2,3-dihydro-4H-1-benzothiopyran-4-one

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The acid from Step C (4.5 g, 15 mmole) was dissolved in 30 ml of thionyl chloride and refluxed for four hours. After cooling the thionyl chloride was concentrated and the residue taken up in carbon tetrachloride. The carbon tetrachloride was concentrated and the residue was taken up in 30 ml of dichloroethane. To the dichloroethane solution being cooled in an ice bath, was added aluminum trichloride (total of 2.1 g, 16 mmole) in three portions every 15 min. After stirring the black solution for an additional 30 min at 0° C., a 5% aqueous HCl solution was added. The aqueous phase was separated and extracted twice with methylene chloride. The organic phases were combined, dried (MgSO4), and concentrated to give the crude product as a yellow oil (3.4 g, 82% yield).

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