Process for the preparation of paliperidone

The present invention provides a process for the preparation of paliperidone or a pharmaceutically acceptable salt thereof, wherein the process comprises condensing a compound of formula (II) with a compound of formula (III) or a salt thereof, in a suitable solvent and a base, in the presence of a catalyst and an inhibiting agent, wherein the inhibiting agent is added to the reaction system before the compound of formula (II) and compound of formula (III) have reacted or as the reaction of the compound of formula (II) and compound of formula (III) is initiated, and optionally converting the paliperidone to a salt thereof, wherein X is a suitable leaving group. The present invention also provides substantially pure paliperidone or a salt thereof, paliperidone or a salt thereof as prepared by the process and uses of the paliperidone or salt thereof.