Patent ID: 7655814

Claim:
A process for producing croconic acid or a salt thereof comprising reacting a hydrocarbon compound consisting of a five-membered ring having an oxo group and/or a monovalent group linked via an oxygen atom selected from the group consisting of cyclopentanol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, cyclopentanone, 1,3-cyclopentanedione, 1,2-cyclopentanedione, 1,2,4-cyclopentanetrione, 3-cyclopentene-1,2-dione, 2,4-cyclopentadiene-1-one, 2-cyclopentene-1-one, 4-cyclopentene-1,3-dione and 3-methoxy-2-cyclopentene-1-one with a halogenating agent.