C1(C)C=CC=CC=1.S(=O)(=O)(O)O.[Cl:13][C:14]1[CH:22]=[C:21]([Cl:23])[CH:20]=[C:16]([C:17]([OH:19])=[O:18])[C:15]=1[OH:24].[C:25](OC(=O)C)(=[O:27])[CH3:26]>O>[C:25]([O:24][C:15]1[C:14]([Cl:13])=[CH:22][C:21]([Cl:23])=[CH:20][C:16]=1[C:17]([OH:19])=[O:18])(=[O:27])[CH3:26]A 1 L, round-bottom, three neck flask equipped with: a mechanical stirrer, a thermometer and a 125 mL dropping funnel with pressure equilibration was placed in a water bath maintained at 65° C. The following reagents were subsequently charged to the flask with an efficient stirring: 250 mL of dry toluene, 2.5 mL of concentrated sulfuric acid and 207 g of well ground, solid 3,5-dichlorosalicylic acid, which forms a mobile suspension. When the temperature of this constantly stirred mixture reached 60° C. (with the water bath temperature maintained at 65° C.) a drop-wise addition of 108 g (100 mL) of acetic anhydride was initiated and completed within 30 min. During the acetic anhydride addition the temperature of the reaction mixture was not allowed to exceed 75° C. After completing the addition, the mixture was stirred and heated to 70° C. for another 4 h. After this time, the agitation was stopped and the mixture cooled over night to room temperature. The white crystals that separated from the mixture were filtered off, washed with 2×10 mL of ice-cold toluene and vacuum dried at 50° C. to yield 206 g (82.7% yield) of 2-acetoxy-3,5-dichlorobenzoic acid. An additional 30.6 g (12.3%% yield) of the product was recovered by: concentrating the filtrate to ½ of the original volume, cooling the solution in an ice-water bath, filtering off the crystalline product and vacuum drying it at 50° C.
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