[Cl-].[Al+3].[Cl-].[Cl-].[Cl:5][C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][C:7]=1[OH:12].[C:13]1(=[O:19])[O:18][C:16](=[O:17])[CH2:15][CH2:14]1.[CH:20](Cl)(Cl)C(Cl)Cl>Cl>[Cl:5][C:6]1[C:7]([OH:12])=[C:8]([CH:9]=[CH:10][CH:11]=1)[C:16]([CH2:15][CH2:14][C:13]([O:18][CH3:20])=[O:19])=[O:17].[Cl:5][C:6]1[CH:11]=[C:10]([CH:9]=[CH:8][C:7]=1[OH:12])[C:16]([CH2:15][CH2:14][C:13]([O:18][CH3:20])=[O:19])=[O:17]
Aluminium chloride powder (66.75 g, 0.5 mole) was added during one hour to a stirred mixture of dry 2-chlorophenol (27.3 g, 0.22 mole), powdered succinic anhydride (20 g, 0.2 mole) and dry sym-tetrachlorethane (150 ml) while the temperature was allowed to rise from 20°C to 40°C. The resultant mixture was heated in an oil bath at 135°C for 2 hours, then cooled in ice and hydrolysed with cold 10% hydrochloric acid solution (100 ml). Tetrachloroethane was removed by steam distillation and the aqueous residue precipitated a gum which was purified by standard procedures to give 31.97 g, 70%, of a mixture of 3-(3-chloro-2-hydroxybenzoyl) propionic and 3-(3-chloro-4-hydroxybenzoyl)propionic acids. Esterification of the mixed acids with methanol - hydrogen chloride and separation of the products by column chromatography (silica, 5/1 chloroform/petroleum ether B.p. 60°-80°C) gave methyl 3-(3-chloro-2-hydroxybenzoyl)propionate (m.p. 60°-62°C) and methyl 3-(3-chloro-4-hydroxybenzoyl)propionate (m.p. 85°-89°C). Hydrolysis of the latter ester with dilute sodium hydroxide solution gave 3-(3-chloro-4-hydroxybenzoyl)propionic acid (m.p. 155°-160°C). The pure acid, on recrystallisation from water, had m.p. 160°-162°C.
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