Use of MEA technology in the synthesis of pharmaceutical compounds: The electrosynthesis of N-acetyl-L-cysteine

The electrosynthesis of N-acetyl-L-cysteine (NAC) from the electroreduction of N,N-diacetyl-L-cystine (NNDAC) using a Polymer Electrolyte Membrane Electrochemical Reactor (PEMER) has been carried out. The Membrane Electrode Assembly (MEA) was formed by a cathode with a catalyst layer made of Pb/C 20 wt% supported on Toray Paper and a catalyst loading of 0.5 mg Pb cm(-2). The anode was a 2 mg Pt cm(-2) gas diffusion anode fed with H(2). The main advantages of this process are: (1) the electrochemical reactor allows to carry out the electrosynthesis without supporting electrolyte, improving in this way the NAC purification and (2) a pronounced decrease of the electrosynthesis energy consumption due to both, the small internal resistance of the PEMER (electrode gap very small and electrolyte very conductive) and the choice of the H(2) oxidation as anodic reaction in stead of the oxygen evolution reaction from water oxidation. The large number of pharmaceutical applications of NAC, as well as the high versatility of the PEMER for electrosynthesis processes, makes interesting the use of MEAs for electroorganic synthesis. (C) 2009 Elsevier B.V. All rights reserved.