Method for the preparation of 5-cyanophthalide

摘要

A method for the preparation of 5-cyanophthalide comprising treatment of a compound of formula IV wherein X is O or S; R¹-R² are each independently selected from hydrogen and C_1-6 alkyl, or R¹ and R² together form a C_2-5 alkylene chain thereby forming a spiro-ring; R³ is selected from hydrogen and C_1-6 alkyl, R⁴ is selected from hydrogen, C_1-6 alkyl, a carboxy group or a precursor group therefore, or R³ and R⁴ together form a C_2-5 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.