Malonyldichloride (168 g, 1.2 mole) was added with stirring to N-cyclohexyl-N'-(2-fluorosulphonylphenyl)urea (270 g, 0.9 mole) in dry chloroform (1500 ml). This mixture was heated for 6 hours at 40°-50° C. and then cooled below 20° C., whereupon 300 ml of methanol were added cautiously. The reaction mixture was then evaporated under reduced pressure yielding 253 g of 1-cyclohexyl-3-(2-fluorosulphonylphenyl)barbituric acid. This sulphofluoride was converted into the sulphonamide as described under b) with a nearly quantitative yield.
