Patent ID: 6958403

Claim:
A method of preparing a pyrazoline compound with the formula (±)-9 wherein each of R 1 and R 3 which may be the same or different is selected from the group consisting of hydrogen, chlorine, fluorine, methyl, trifluoromethyl and methoxy; and each of R 2 and R 4 which may be the same or different is selected from the group consisting of hydrogen, chlorine, fluorine, methyl, trifluoromethyl, methoxy, trifluoromethoxy, methylsulphonyl, aminosulphonyl and sodium sulphonate; and with the condition that one of the substituents R 2 or R 4 is a sodium sulphonate group (SO 3 Na); said method comprising: (a) reacting a pyrazoline compound with the formula (±)-10 wherein each of R 1 and R 3 which may be the same or different is selected from the group consisting of hydrogen, chlorine, fluorine, methyl, trifluoromethyl and methoxy; and each of R 2 and R 4 which may be the same or different is selected from the group consisting of hydrogen, chlorine, fluorine, methyl, trifluoromethyl, methoxy, trifluoromethoxy, methylsulphonyl and aminosulphonyl; with the condition that one of the substituents R 2 or R 4 represents an atom of hydrogen; with chlorosulphonic acid, without a solvent or with a chlorinated solvent at temperatures between 0° C. and 100° C. to form an intermediate compound; and (b) reacting said intermediate compound with sodium hydroxide resulting in the pyrazoline with the formula (±)-9.