Synthesis of several 2,7-dibromoacridine derivatives, including 4-[2-(succinimidyloxycarbonyl)ethyl]phenyl 2,7-dibromo-10-methylacridinium-9-carboxylate trifluoromethanesulfonate

The reaction of bis(4-bromophenyl)amine and oxalyl chloride gave N-(4-bromophenyl)-5-bromoisatin, which on treatment with potassium hydroxide yielded 2,7-dibromoacridine-9-carboxylic acid. Treatment of acridine- 9-carboxylic acid with freshly redistilled thionyl chloride followed by reaction with benzyl 3-(4- hydroxyphenyl)propanoate gave the corresponding benzyl ester. Hydrolysis of the benzyl ester gave the corresponding acid, which, on reaction with N-hydroxysuccinimide in the presence of dicyclohexylcarbodiimide, gave the corresponding ester. Finally, methylation of the N-hydroxysuccinimide ester gave the corresponding 10-methylacridinium trifluoromethanesulfonate.