Process for the preparation of 2-alkylsulfonyl substituted benzoic acid derivatives

A process for the preparation of a compound of formula (I):

• wherein
• R1 represents C1-6 alkyl, C1-6 haloalkyl, phenyl or phenyl substituted with carboxylic acid;
• R2 represents hydrogen, C1-6 alkyl, C1-6 haloalkyl, C1-6 haloalkoxy, phenyl or phenyl substituted with halogen, carboxylic acid;
• which comprises
• a) reacting a compound of formula (II):
• wherein R1, and R2 are as hereinbefore defined;
• with an oxidizing reagent in the presence of an aqueous acid in a suitable solvent system to form a compound of formula (III) and the reaction is processed in the absence of a metal catalyst;
• wherein R1, and R2 are as hereinbefore defined;
• b) reacting the compound of formula (III) with an alkali hydroxide;
• c) mixing the reaction mixture from step (b) with a strong acid system to obtain the compound of formula (I).