Journal of the Electrochemical Society, Vol.146, No.4, 1492-1495, 1999
Cathodically promoted addition of nitroalkanes to ferrocenecarboxaldehyde
The addition of ferrocenecarboxaldehyde, 5, to nitromethane and nitroethane has been studied through the use of cathodically generated superoxide as an electrogenerated base to catalyze the reaction. The electrolyses were conducted in the pure nitroalkane as solvent. The nitroalcohol obtained from nitromethane, (1-hydroxy-2-nitroethyl)ferrocene, (6), was produced in higher yield than obtained in earlier work. Approximately equal amounts of the two diastereomers of (1-hydroxy-2-nitropropyl)ferrocene (8) were produced from reaction with nitroethane. The threo isomer was separated and crystallized, and its stereochemical identity was proven by X-ray crystallography. Conditions were found for which reaction of 5 with nitromethane produced the double addition product, [2-nitro-1-(nitromethyl)ethyl]ferrocene, 7, in almost quantitative yield. Reversible potentials for oxidation of the ferrocene moiety of 5-8 and other ferrocene derivatives were measured by means of cyclic voltammetry in acetonitrile. The nitroalcohols (6 and 8) are only slightly more difficult to oxidize than ferrocene (75 and 65 mV, respectively) whereas the potential for 1,3-dinitro compound 7 is 140 mV positive of that of ferrocene. Irreversible reduction peak potentials are also reported.