Preparation of dyes derived from Eriochrome Red B and Acid Alizarin Violet N soluble in organic solvents

Both hydroxy groups of Eriochrome Red B are protected by acetylation and the sulfonic acid group is converted to the sulfonyl chloride with phosphorus pentachloride. Reaction with dibutylamine or N-butylbenzeneethanamine followed by the deprotection gives red azo dyes 7a or 7b, readily soluble in chloroform and toluene. A similar procedure applied to Acid Alizarin Violet N gives only a multicomponent mixture. Friedel-Crafts reaction between dibutylsulfamoyl chloride and 2-nitrophenol gives N,N-dibutyl-4-hydroxy-3-nitrobenzenesulfonamide (11). Reduction of the nitro group gives amine 14 which is diazotized and coupled with 2-naphthol to give the required dye 13 giving deep-red solutions in methanol, chloroform and acetone.