[NH2:1][C:2]1[C:10]([Cl:11])=[CH:9][C:5]([C:6]([OH:8])=[O:7])=[C:4]([OH:12])[CH:3]=1.C[O-].[Na+].CO.S(OC)(O[CH3:22])(=O)=O>CO.O>[NH2:1][C:2]1[C:10]([Cl:11])=[CH:9][C:5]([C:6]([O:8][CH3:22])=[O:7])=[C:4]([OH:12])[CH:3]=1A solution of 4-amino-5-chloro-2-hydroxybenzoic acid (1.88 g, 10 mmol) in absolute methanol (20 mL) was treated with 25% sodium methoxide/methanol (2.16 g, 10 mmol), stirred for 30 minutes, and concentrated in vacuo. The solid residue was taken up in anhydrous acetone (30 mL), treated with dimethyl sulfate (1.64 g, 13 mmol), and refluxed for 2 hours. The resultant solution was diluted with water (100 mL), and the precipitate was filtered, washed with water, and dried exhaustively in vacuo to afford 1.75 g (87%) of fine colorless needles. The material was recrystallized from ethyl acetate/hexane; mp 138°-139° C.
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