A method for the preparation of 5-cyanophthalide comprising treatment of a compound
of formula IV
##STR1##
wherein X is O or S;
- R1-R2 are each independently selected from hydrogen
and C1-6 alkyl, or R1 and R2 together form a C2-5
alkylene chain thereby forming a spiro-ring; R3 is selected from
hydrogen and C1-6 alkyl, R4 is selected from hydrogen, C1-6
alkyl, a carboxy group or a precursor group therefore, or R3 and
R4 together form a C2-5 alkylene chain thereby forming a
spiro-ring; with a dehydration agent or alternatively where X is S, thermally cleavage
of the thiazoline ring or treatment with a radical initiator, such as peroxide
or with light, to form 5-cyanophthalide, which is an important intermediate used
in the preparation of the antidepressant drug citalopram.
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