A synthetic route to 3-(dialkylamino)phenothiazin-5-ium salts and 3,7-disubstituted derivatives containing two different amino groups

Phenothiazin-5-ium tetraiodide hydrate ( 2 ), the suggested oxidation product of phenothiazine with iodine, is treated with two equivalents of a dialkylamine to give 3-(dialkylamino)phenothiazin-5-ium triiodides, 3-6 . 3,7-Disubstituted phenothiazin-5-ium iodides, 7-9 , are obtained by the reaction of 3-6 with an amine.