Process for the preparation of one or more compounds of thiopyridinone type

Process for the preparation of at least one compound of following formula (I):

• in which formula (I):
• A represents a saturated or unsaturated, preferably saturated, cyclic or acyclic, preferably acyclic, linear or branched, divalent hydrocarbon chain comprising from 1 to 10 carbon atoms, optionally interrupted by one or more heteroatoms, such as an oxygen atom or a sulfur atom, or groups chosen from an NR2 or (thio)carbonyl group, or their combinations, such as thioester, with R2 representing a hydrogen atom or a C1-C4 alkyl group;
• M represents a hydrogen atom, an alkali metal or alkaline earth metal, an ammonium group;
• R1 represents a hydrogen atom, a linear or branched C1-C10 alkyl group, optionally substituted by an OR3, SR3 group with R3 corresponding to a hydrogen atom or a linear or branched C1-C10 alkyl group,
• and also one of its optical isomers, geometrical isomers and tautomers, and also one of its organic or inorganic acid or base salts, and one of its solvates, such as hydrates;
• said process taking place according to the following synthesis scheme (1):
• in which:
• Hal and Hal′, which are identical or different, represent a halogen atom, and
• M, A and R1 have the same meanings as in the formula (I);
• at least stage (iii) is at acidic pH, i.e. less than 7.