O.P([O-])(O)(O)=O.[Na+].OO.Cl([O-])=O.[Na+].[Cl:14][C:15]1[C:24]([CH:25]=[O:26])=[C:23]([Cl:27])[CH:22]=[CH:21][C:16]=1[C:17]([O:19][CH3:20])=[O:18].Cl.S([O-])(O)=[O:30].[Na+]>O.C(#N)C>[Cl:14][C:15]1[C:24]([C:25]([OH:30])=[O:26])=[C:23]([Cl:27])[CH:22]=[CH:21][C:16]=1[C:17]([O:19][CH3:20])=[O:18]At 5° C., 5.9 g (0.043 mol) of sodium dihydrogen phosphate monohydrate in 70 ml of water, 20.5 g (0.181 mol) of 30% strength hydrogen peroxide solution and 27.3 g (0.241 mol) of 80% strength sodium chlorite solution were added in succession to a solution of 40.0 g (0.172 mol) of methyl 2,4-dichloro-3-formylbenzoate and 500 ml of acetonitrile. The reaction solution was stirred for 1 hour at 5° C. and for 12 hours at room temperature. Subsequently, the pH was adjusted to 1 with 10% strength hydrochloric acid and 500 ml of 40% strength sodium hydrogen sulfite solution were added. After stirring for 1 hour at room temperature, the aqueous phase was extracted three times with ethyl acetate and the combined organic phases were washed with 1.0 l of 10% strength sodium hydrogen sulfite solution and then dried. Removal of the solvent by distillation gave 40.0 g of methyl 2,4-dichloro-3-hydroxycarbonylbenzoate. (1H NMR (d6-DMSO, δ in ppm): 3.90 (s, 3H); 7.69 (d, 1H); 7.89 (d, 1H).)
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