[Cl:1][C:2]1[C:11]([CH:12]=[N:13][OH:14])=[C:10]([S:15]([CH3:18])(=[O:17])=[O:16])[CH:9]=[CH:8][C:3]=1[C:4]([O:6][CH3:7])=[O:5].Cl[O-].[Na+].[C:22]([O-])(=[O:24])[CH3:23].[Na+].C(=O)C>C(Cl)Cl>[Cl:1][C:2]1[C:11]([C:12]2[O:24][CH:22]([CH3:23])[O:14][N:13]=2)=[C:10]([S:15]([CH3:18])(=[O:17])=[O:16])[CH:9]=[CH:8][C:3]=1[C:4]([O:6][CH3:7])=[O:5]8.0 g (27.4 mmol) of methyl 2-chloro-3-(hydroxyiminomethyl)-4-methylsulfonylbenzoate in 150 ml of methylene chloride were admixed dropwise with 16.0 g (27.4 mmol) of a 12.5% strength sodium hypochlorite solution, and a spatula-tip of sodium acetate was added. After 1 hour, 34.4 g (0.74 mol) of acetaldehyde were added a little at a time within a period of 36 hours, and the mixture was slowly heated to 55° C. The mixture was subsequently stirred at room temperature for 48 hours, washed with water, dried and concentrated. The residue was then taken up in methylene chloride, 10.0 g (0.23 mol) of acetaldehyde and a spatula-tip of sodium acetate were added and the mixture was heated under reflux for 8 hours. After 72 hours, a further 10.0 g (0.23 mol) of acetaldehyde were added and the mixture was stirred at room temperature. The mixture was subsequently washed with water, dried and concentrated. The residue was passed through silica gel (eluent: isopropanol:cyclohexane=1:9). This gave 5.0 g (55% of theory) of methyl 2-chloro-3-(2-methyl-2H-1,3,4-dioxazol-5-yl)-4-methylsulfonylbenzoate.
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