3-Pyridineacetic acid → Risedronate

Participants

Reaction Conditions

Reaction Steps

3-Pyridine acetic acid (100 g) added to acetonitrile (1.0 L). To the reaction mixture was added phosphorous acid (142 g). The reaction mass was heated up to reflux temperature (70-75° C.). To this phosphorous trichloride (271 g) was added slowly at 70° C. and the reaction mass was refluxed for 5.0 hours. The solvent was distilled off completely under vacuum. Demineralized water (400 ml) was added to the reaction mass at ambient temperature and charcoalised. The filtered mass was refluxed for 4.0 hours at 85° C. The reaction mass was cooled to 0-5° C. and stirred for 2 hours. It was filtered and washed with demineralized water to get risedronic acid as a white crystalline solid. The wet material was dissolved in demineralized water (300 ml) and 50% sodium hydroxide solution was added to reaction mass to make the pH basic, charcoalised and acidified with concentrated hydrochloric acid. The reaction mass was stirred further for 1.0 hour. The solid was filtered, washed with demineralized water to get the pure risedronic acid (160 g, yield 77.33%) having purity of 99.25% by HPLC.

Provenance & Evidence