Process for the synthesis of Dapsone and its intermediates

A process for the synthesis of Dapsone comprising the following steps:

• a) a condensation reaction between a compound of formula (II)
• with a compound of formula (III)
• to give a compound of formula (IV)
• in the presence of a base in an aprotic polar solvent, and a catalytic amount of an amine in apolar solvent;
• wherein:
• R1 is selected from the group consisting of H atom and an acetyl group,
• X is selected from the group consisting of F, I, Cl and Br,
• and
• R2 is selected from the group consisting of a linear C1-10 alkyl and a branched C1-10 alkyl;
• b) b.i)—the oxidation reaction to sulfone of a compound of formula (IV), to give a compound of formula (V)
• and
• the hydrolysis reaction of a compound of formula (V) to give a compound of formula (VI)
• in the presence of a base in a solvent;
• or
• b.ii)—a saponification reaction of the compound of formula (IV) to give the compound of formula (XIII)
• in the presence of a base in a solvent
• and
• an oxidation reaction to sulfone of the compound of formula (XIII) to give the compound of formula (VI);
• c) the conversion of the compound of formula (VI), into the corresponding hydroxamic acid of formula (VII)
• by reaction with hydroxylamine hydrochloride, in the presence of a condensing agent in a polar aprotic solvent;
• d) the Lossen rearrangement reaction of the compound of formula (VII) to give the compound of formula (VIII)
• e) the reaction of the compound of formula (VIII) with:
• an alcohol to give a compound of formula (IX)
• wherein
• R3 is selected from the group consisting of a C1-10 linear alkyl and a C1-10 branched alkyl;
• or
• with water to give the compound of formula (X)
• f) deprotection of the functional groups of compound of formula (IX) or (X) to give Dapsone.