Indirect Electrochemical Cyclisation of Bromoalkoxylated Derivatives using Environmentally Friendly Methodologies

The electrochemical intramolecular cyclization of bromoalkoxylated derivatives 1 using Ni(II) complex as mediator of electron transfer was carried out in ethanol by constant-current electrolysis in one-compartment cell in the absence of sacrificial anodes as an environmentally friendly systems. It is demonstrated that the electroreduction reaction of bromoalkoxylated derivatives was catalyzed by the electrogenerated Ni(I) complexes. Only cyclization to the five-membered-ring esters was obtained in moderate to good yields as the main products. Functionalyzed tetrahydrofurans are important intermediates in the synthesis of natural products such as lignans. A mechanistic scheme is proposed to explain the results obtained by means of cyclic voltammetry and constant-current electrolysis.