C([O:3][C:4](=[O:23])[CH2:5][C:6]([C:9]1[CH:14]=[CH:13][C:12]([C:15]2[CH:20]=[CH:19][C:18]([F:21])=[CH:17][C:16]=2[F:22])=[CH:11][CH:10]=1)(O)[CH3:7])C.O.O.Cl[Sn]Cl.Cl.[OH-].[Na+].S>C(O)(=O)C>[F:22][C:16]1[CH:17]=[C:18]([F:21])[CH:19]=[CH:20][C:15]=1[C:12]1[CH:13]=[CH:14][C:9]([CH:6]([CH3:7])[CH2:5][C:4]([OH:23])=[O:3])=[CH:10][CH:11]=13.2 g. of 3-(2',4'-difluoro-4-biphenylyl)-3-hydroxybutyric acid ethyl ester are dissolved in 40 ml. of acetic acid. The solution is poured into a solution of 9 g. of SnCl2.2H2O in 20 ml. of concentrated hydrochloric acid. The mixture is heated under reflux for 3 hours and adjusted to pH 2 with sodium hydroxide solution. Hydrogen sulfide is passed in until no more SnS precipitates and the mixture is filtered and worked up in the customary manner to give 3-(2',4'-difluoro-4-biphenylyl)butyric acid, m.p. 109°-110°.
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