Method for the preparation of pure citalopram

A process for the preparation of citalopram

• 9
• in which a compound of formula II
• 10
• wherein Z is iodo, bromo, chloro or CF3—(CF2)n—SO2—O—, n being 0, 1, 2, 3, 4, 5, 6, 7 or 8, is subjected to a cyanide exchange reaction with a cyanide source;
• the resultant crude citalopram product is optionally purified and subsequently treated with an amide or an amide-like group forming agent selected from the compounds of Formulas (a), (b) or (c):
• 11
• where X is halogen or a group O—CO—R′, Hal is halogen, Y is O or S, W is O, N or S and R, R′, R″ and R′″ are each selected from the group consisting of hydrogen, alkyl, and optionally substituted aryl or aralkyl;
• the reaction mixture is then subjected to an acid/base wash or crystallisation and recrystallisation of citalopram in order to remove amides formed from the crude citalopram mixture;
• and
• the resulting citalopram product is optionally purified and isolated as the base or a pharmaceutically acceptable salt thereof.