[CH3:1][N:2]([C:4]([NH:6][C:7]1[S:8][C:9]([C:12]([F:15])([F:14])[F:13])=[N:10][N:11]=1)=[O:5])[NH2:3].[CH2:16]=O.[OH-].[K+]>CO>[CH3:1][N:2]1[C:4](=[O:5])[N:6]([C:7]2[S:8][C:9]([C:12]([F:15])([F:13])[F:14])=[N:10][N:11]=2)[CH2:16][NH:3]1The 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)semicarbazide prepared in Example 2 was dissolved in methanol (100 ml) in a glass reaction flask equipped with a mechanical stirrer and thermometer. Aqueous formaldehyde (12 ml; 37% concentration) was then added to the flask with stirring. The reaction mixture warmed to a temperature of about 35° C. Sufficient aqueous potassium hydroxide was then added to adjust the pH of the reaction medium to from about 7 to 8. A solid precipitate was formed. The precipitate was then recovered by filtration, was recrystallized from an ethyl acetate-heptane mixture and was dried under vacuum to yield the desired product 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one having a melting point of 187° to 188° C.
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