Process for the preparation of methylene blue

Abstract

Provided herein is a process for preparation of 3,7-bis-(dimethy-lamino)-phenothiazin-5-ium chloride: Formula (I). The said process comprises preparing 3,7-dibromophenothiazin-5-iumbromide wet Crude(III) from phenothiazine (II) alongpro-moter, catalyst and brominating agent in presence of organic solvent; preparing 3,7-bis-(dimethylamino)-phenothiazin-5-ium bromide (IV) from 3,7-dibromophenothiazin-5-ium bromide; preparing 3,7-bis(Dimethylamino)-phenothiazin-5-ium chloride from 3,7-bis-(dimethylamino)-phenothiazin-5-ium bromide and subsequently purifying and removing metal content through metal scavenger from 3,7-bis-(dimethylamino)-phenothiazin-5-ium chloride (I). The present process eliminates the additional step of ion exchange column in the reaction and provides 99 to 99.5 percentage of product purity.

Dependencies are inferred from the claim text.