Purification of α,β-unsaturated carboxylic acids as their potassium carboxylate salts using dry column vacuum chromatography

Carboxylic acids are ubiquitous functional groups and are used widely in the bulk chemistry and fine pharmaceutical industries. During the development of novel methodology for the synthesis of α,β-unsaturated carboxylic acids, it was found that established methods for the purification of the product carboxylic acids led to unsatisfactory outcomes. However, chromatographic purification of the products of these reactions as their potassium carboxylate salts proved highly successful. Unlike their parent carboxylic acids, the carboxylate salts could be separated readily from the other constituents of the reaction mixture using dry column vacuum chromatography (DCVC). The yields of the carboxylic acid products obtained by subsequent protonation of the carboxylate salts were found to depend strongly on the identity of the acid used to effect the protonation, with methanesulfonic acid and (+) camphorsulfonic acid resulting in the highest recoveries of pure products. The combined DCVC and acidification protocols developed were shown to be effective for the purification of numerous functionalised α,β-unsaturated carboxylic acids