Dry acetone (1500 ml) was added to a mixture comprising bis(2-chloro-4-fluoro-5-aminophenyl)carbonate (233 g, 0.68 mol) and potassium carbonate (188 g, 1.36 mol), and methyl chloroformate (126 g, 1.33 mol) was dropwise added to the resulting solution, and the mixture was heated at 60° C. for 4 hours with stirring. After reaction, acetone was removed by distillation under reduced pressure, acetic acid was added so that the reaction mixture was made acidic, and thereafter the acidic mixture was poured into ice-water. The solid as precipitated out was taken out by filtration, washed with water and fully dried to obtain a white solid of bis(2-chloro-4-fluoro-5-methoxycarbonylaminophenyl)carbonate (279 g, 0.60 mol). Yield: 88.2 %. Spectral data and other data of the product are those as shown in Example 11.
