Electrochemical conversion of 4-phenylbuten-2-ones into 4-phenylbutan-2-ones. Electrocatalytic hydrogenation at a nickel surface

The electrocatalytic hydrogenation of 4-(4-hydroxyphenyl)buten-2-one at a nickel cathode in aqueous ethanol containing sulphuric acid has been examined. HPLC was used for the analysis of reaction mixtures. The product composition is critically dependent on the method used for electrodeposition of the nickel-black surface. An electrochemically deposited nickel-black will catalyse the electrochemical hydrogenation of this substrate. Formation of 4-(4-hydroxyphenyl)butan-2-one is favoured at high concentrations of substrate and a minor amount of the corresponding secondary alcohol is also formed. The process was applied also to hydrogenation of 4-(4-methoxyphenyl)buten-2-one and 4-(4-hydroxy-3-methoxyphenyl)buten-2-one with 63-68% current efficiency. An alternative process, the reduction of these enones at a lead cathode in presence of sodium hydrogen carbonate, gave an unsatisfactory mixture of products. (C) 1997 Elsevier Science Ltd.