Process for the preparation of 2,4,5-trifluorophenylacetic acid

Process for the preparation of 2,4,5-trifluorophenylacetic acid of formula (I) or a salt thereof:

• comprising the following steps:
• (a) halogenation of the compound of formula (VII):
• in which X is a halogen atom,
• to give the compound of formula (V):
• in which X and X′ are independently halogen atoms,
• and/or the compound of formula (VI):
• in which X and X′ are independently halogen atoms,
• (b) dehydrohalogenation of the compound/s of formula (V) and/or of formula (VI) obtained in the step (a) to give the compound of formula (IV):
• in which X is a halogen atom;
• (c) conversion of the compound of formula (IV) obtained in the step (b) into the compound of formula (II):
• in which R is a linear or branched C1-C5 alkyl or is an aryl or benzyl group;
• and/or into the compound of formula (III):
• in which X is a halogen atom and R is a linear or branched C1-C5 alkyl or is an aryl or benzyl group;
• (d) hydrolysis of the compound/s of formula (II) and/or of formula (III) obtained in the step (c) to give the compound of formula (I) or salts thereof:
• or, alternatively to the steps (c) and (d) the following step:
• (e) direct hydrolysis of the compound of formula (IV) obtained in the step (b) to give the compound of formula (I) or salts thereof.