[CH3:1][O:2][C:3](=[O:15])[C:4]1[CH:9]=[CH:8][C:7]([OH:10])=[C:6]([CH2:11][CH2:12][CH3:13])[C:5]=1[OH:14].[Cl:16]N1C(=O)CCC1=O.O>C(Cl)(Cl)(Cl)Cl>[CH3:1][O:2][C:3](=[O:15])[C:4]1[CH:9]=[C:8]([Cl:16])[C:7]([OH:10])=[C:6]([CH2:11][CH2:12][CH3:13])[C:5]=1[OH:14]A solution of 2.1 g (0.01 mol) of 2,4-dihydroxy-3-propylbenzoic acid methyl ester and 1.6 g (0.012 mol) of N-chlorosuccinimide in 50 mL of carbon tetrachloride was stirred at reflux for 9.5 hours. Additional N-chlorosuccinimide (1.6 g) was added and reflux was continued for 17 hours. 0.8 g of N-chlorosuccinimide was added and reflux was continued for 8 hours. Water was added. The organic layer was separated and washed with sodium thiosulfate solution, sodium bicarbonate solution, dried and concentrated under reduced pressure to give 5-chloro-2,4-dihydroxy-3-propylbenzoic acid methyl ester. Recrystallization from hexane gave analytically pure material, mp 75°-76°.
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