Patent ID: 7855287

Claim:
A synthetic process for the preparation of N-alkylsulfonates of phenothiazine of formula (I): where M + is a monovalent, polivalent, organic or inorganic cation, R 1 and R 2 are independently from each other H, linear or branched, substituted or unsubstituted alkyl radicals having a number of carbon atoms between 1 and 6, and linear or branched, substituted or unsubstituted alkyl ether radicals having a number of carbon atoms between 1 and 6, and n is an integer ≧2, wherein the process comprises the following steps: a. the preparation of the anion of phenothiazine, b. the reaction of said anion with a cyclic alkylsulfonic ester (sultone), with precipitation of said N-alkylsulfonates of phenothiazine of formula (I) in crystalline form, wherein the preparation of the anion of phenothiazine in step a, takes place in situ in a solution containing phenothiazine and an organic solvent by addition of a base, and wherein said cyclic alkylsulfonic ester is a four- to seven-membered ring.