Patent ID: 7332603

Claim:
A process for preparing bisphosphonic acids and their salts of formula in which R 1 has the meanings indicated in the following Table 1: R 1 = CH3, Etidronic acid Zoledronic acid Risedronic acid Minodronic acid Pamidronic acid Alendronic acid Neridronic acid Olpadronic acid Ibandronic acid and in which M 1 , M 2 , M 3 , M 4 are selected from H, and a monovalent cation, comprising the reaction of acids of formula R 1 -CO 2 H, in which R 1 has the aforesaid meanings, with acids and phosphorus trichloride, wherein the reaction is conducted in ionic liquids as the reaction solvents, at a temperature of between 15° C. and 120° C. wherein said ionic liquids are selected from the group consisting of salts of ammonium, sulphonium or phosphonium having the following formulas in which each R may be independently a linear or branched C 1 —C 20 alkyl group, a cycloalkyl containing from 5 to 6 carbon atoms, alkylene aryl, or aryl; R 2 is H or a linear or branched C 1 —C 18 alkyl group, X − is an anion selected the group consisting of halogenide, BF 4 − , PF 6 − , and AlCl 4 − .