Intermediates for the preparation of pramipexole

A process for the preparation of pramipexole, or a pharmaceutically acceptable salt thereof, comprising the acylation of a compound of formula (VII), either as the single (S) enantiomer or as mixture of (R,S) enantiomers

• wherein R3 is hydrogen and Ra is a free or protected amino group, by reaction with propionic anhydride, and subsequent reduction of the resulting compound of formula (IX)
• wherein Ra is as defined above, by treatment with an alkali metal borohydride and molecular iodine, to obtain a compound of formula (VIII)
• wherein R3 is hydrogen and Ra is as defined above;
• followed, if necessary, by deprotection of the primary amino group and/or by resolution of the mixture of (R,S) enantiomers into the single (S) enantiomer and, if desired, by conversion of pramipexole to a pharmaceutically acceptable salt thereof.