Electro-organic chemistry of fullerenes. Part 1. Indirect cathodic reduction of vic-dihalides and perfluoroalkyl halides using C 60 as mediator. Cyclic voltammetric study and preparative-scale electrolysis

Abstract

Although a number of electrochemical studies on the redox behaviour of C 60 and its derivatives have been carried out, there has been no report dealing with C 60 as a redox mediator for preparative-scale indirect cathodic reduction of organic molecules. In this work, C 60 was studied as a redox mediator by both cyclic voltammetry and preparative-scale electrolysis. It was suggested that meso-1,2-dibromo-1,2-diphenylethane could be reduced by electrogenerated C 60 3− while erythro-ethyl-2,3-dibromo-3-phenylproponate and 4meso-diethyl 2,3-dibromosuccinate could be reduced by electrogenerated C 60 2− by cyclic voltammetric studies of C 60 and these bromides. Cyclic voltammetric study also showed that perfluoroalkyl iodide and bromide could be reduced catalytically by electrogenerated C 60 2− and C 60 3− respectively. Preparative indirect cathodic reduction of these vic-dibromides using a catalytic amount (0.02 to 0.04 mol per mol substrate) of C 60 as mediator provided the corresponding olefines in good yield and with high current efficiencies. However, preparative indirect cathodic reduction of perfluorohexyl halides failed because of the strong passivation of the cathode. Thus, C 60 was shown to work as an efficient mediator for preparative-scale indirect cathodic reduction. It is noted that C 60 is a potential power-variable organic reagent since the reducing power of C 60 anion can be easily changed electrochemically without any modification of the C 60 molecule.