Patent ID: 6911548

Claim:
A method for the preparation of 5-cyanophthalide comprising reacting a compound of Formula IV wherein X is O or S; R 1 -R 2 are each independently selected from hydrogen and C 1-6 alkyl, or R 1 and R 2 together form a C 2-5 alkylene chain thereby forming a spiro-ring; R 3 is selected from hydrogen and C 1-6 alkyl, R 4 is selected from hydrogen, C 1-6 alkyl, a carboxy group or R 3 and R 4 together form a C 2-5 alkylene chain thereby forming a spiro-ring; with a dehydration agent or alternatively where X is S, by thermal cleavage of the thiazoline ring or treatment with a radical initiator, to form 5-cyanophthalide having the formula