Derivatization of carboxylic acids by reaction with 4'-bromophenacyl trifluoromethanesulfonate prior to determination by high-performance liquid chromatography.

The use of 4'-bromo-2-hydroxyacetophenone trifluoromethanesulfonate ester (4'-bromophenacyl triflate) in the preparation of carboxylic acid 4'-bromophenacyl ester derivatives for spectrophotometric detection in high-performance liquid chromatography is described. The reagent is prepared in 66% yield by the reaction of 4'-bromo-2-diazoacetophenone with trifluoromethanesulfonic acid in anhydrous sulfur dioxide and is stable for 3-6 months. Reactions of 10(-6) M carboxylate N,N-diisopropylethylammonium salts with this reagent in acetonitrile at room temperature proceed to completion in 1-5 min. Optimal rates of reaction are obtained with a 10-fold equivalent excess of alkylating agent and 5 equivalents of N,N-diisopropylethylamine present. The process has been applied successfully to mono-, di- and tricarboxylic and sterically hindered carboxylic acids.