Cl[O-].[Na+].[OH-].[K+].[F:6][CH:7]([F:19])[O:8][C:9]1[CH:14]=[CH:13][C:12]([C:15](=[O:17])C)=[C:11]([CH3:18])[CH:10]=1.S(S([O-])=O)([O-])(=O)=[O:21].[Na+].[Na+].Cl>>[F:19][CH:7]([F:6])[O:8][C:9]1[CH:14]=[CH:13][C:12]([C:15]([OH:17])=[O:21])=[C:11]([CH3:18])[CH:10]=1A stirred solution of sodium hypochlorite (5.25% Aqueous, 204 mL, 143 mmol) and 2N aqueous KOH (22 mL, 44 mmol) are heated to 50° C. and 1-(4-difluoromethoxy-2-methyl-phenyl)-ethanone (A4) (5.8 g, 29 mmol) is added. After maintaining the temperature at 50-70° C. for 3 h and keeping at RT overnight, the reaction is reheated to 50° C. and sodium metabisulfite (4.5 g) is added in 3 portions. The reaction is then acidified with 12N HCl and stirred well. The precipitated white solid is filtered off, rinsed with a little water and air dried to afford 4-difluoromethoxy-2-methyl-benzoic acid (242) (5.4 g, 92%). The product is recrystallized from 1:1 mixture of ACN and water. mp: 117-119° C. Elemental Analysis: Actual C (53.23), H (3.88), F (18.66) Theoretical C (53.47), H (3.99), F (18.80).
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