Indirect electrochemical synthesis of p-hydroxyphenylacetic acid

p-Hydroxyphenylacetic acids are used in the synthesis of pharmaceutical dru gs such as atenolol betaxolol, or bufexamac. In this work, the indirect ele ctrosynthesis of p-hydroxyphenylacetic acid is carried out using the redox system Cr(II)/Cr(III) as a mediator. Effluents that are not contaminated by chromium salts are obtained because the reductant, Cr(II), can be electroc hemically regenerated. Voltammetric and galvanostatic studies were performe d to find the best reaction conditions for the reduction of Cr(III) to Cr(I I). An "ex-cell" procedure has been used for this process. Current efficien cy, for Cr(II) synthesis, higher than 90% was reached using a bismuth-doped carbon-felt electrode. In the chemical reduction of the p-hydroxymandelic acid by electrochemically generated Cr(II), the presence of a cosolvent, re action temperature, and molar Cr(II)/p-hydroxymandelic acid relationship wa s investigated. High material conversion and nearly quantitative yield was obtained at 90 degrees C using 2-propanol as the cosolvent.