Process for Preparing Diaminophenothiazinium Compounds

A process for preparing a compound corresponding to formula (I) below:

• in which each of R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 is chosen, independently of the others, from the group constituted of:
• a hydrogen atom,
• saturated or unsaturated, linear, or branched C1-C6 alkyl groups, or C3-C6 cycloalkyl groups, optionally substituted with one or more functions chosen from a halogen atom, and a C1-C6 alkoxy, C1-C6 alkoxycarbonyl or —CONH2 function,
• aryl groups optionally substituted with one or more functions chosen from:
• a C1-C4 alkyl, a halogen atom, and a C1-C6 alkoxy, C1-C6 alkyloxycarbonyl or —CONH2 function,
• X− represents an organic or inorganic anion,
• wherein the process comprises at least one step during which a compound of formula (II):
• in which R represents a group chosen from:
• a phenyl or benzyl group, optionally substituted with one or more functions chosen from:
• a C1-C4 alkyl, a halogen atom, a C1-C4 haloalkyl and a nitro group,
• a phenyloxy or benzyloxy group optionally substituted on the aromatic nucleus with one or more functions chosen from:
• a C1-C4 alkyl, a halogen atom, a C1-C4 haloalkyl and a nitro group,
• Z represents an atom chosen from O and S,
• is subjected to a purification step, this step comprising at least one filtration through a filtration support chosen from:
• a silica gel, a neutral, basic or acidic alumina gel, a microporous membrane, a resin grafted with metal-capturing groups, and fibers grafted with metal-capturing groups,
• and thereafter a step for deprotection of the amine of the phenothiazine ring of the compound of formula (II).