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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-methoxy-phenyl)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.

One electron reduction of aryl halides is known to generate the aryl radical and halide ion. These aryl radicals will cyclize onto an adjacent benzene ring in a reaction that is potentially useful in organic synthesis and which is well documented at a mercury cathode. 5-(2-Halophenyl)-1-(4-fluorophenyl)tetrazoles are used here as representative substrates and the cyclization reaction to 7-fluorotetrazolo[1,5-f]phenanthridine is developed at cathodes of cadmium, zinc and mild-steel. A high yield of the desired cyclization product is achieved using a mild-steel cathode and a sacrificial magnesium anode in an undivided cell with acetonitrile, 0.1 M tetraethyl ammonium tetrafluoroborate as electrolyte and under an air atmosphere.

Non-stoichiometric manganese dioxide prepared electrochemically at room temperature and suspended in dilute sulphuric acid is used to oxidise isosafrole to piperonal in 54% isolated yield. The manganese dioxide-manganese(II) sulphate system can be recycled electrochemically at high current density. It has the further advantage that water-soluble materials derived from the chemical oxidation step can be removed by filtration at the manganese dioxide stage. Direct oxidation of isosafrole at a lead dioxide anode leads to further oxidation of the piperonal.