INDUSTRIAL PROCESS FOR THE SYNTHESIS OF 2-SUBSTITUTED 1-(HYDROXY-ETHYLIDENE)-1,1-BIS-PHOSPHONIC ACIDS OF HIGH PURITY AND THE SALTS THEREOF

摘要

Process for the synthesis of high purity 2-substituted-1-(hydroxy-ethylidene)-1,1-bisphosphonic acid of formula (I), the salts and hydrates thereof - wherein the meaning of R is 3'-pyridyl or 2'-amino-ethylidene group - from compounds of formula (II) - wherein the meaning of R is as described above - or salts and hydrates thereof with phosphorous acid in the presence of methanesulfonic acid using phosphorus pentoxide as reagent and in given case the obtained acid is converted into a salt with base.