Electrochemical reduction of tertiary nitroalkanes to amines.

Abstract

Electrochemical reduction of tertiary nitroalkanes, 2-substituted-1, 1-dimethyl-1-nitroethanes (1), was investigated in aqueous buffer solutions. In polarography, 1 with a phenyl group and/or a hydroxyl group at the 2-position showed an ill-defined wave in the weakly acidic and neutral pH region at relatively high negative potentials, in addition to a well-defined wave arising from the reduction of 1 to the corresponding hydroxylamine (2). Controlled potential electrolysis of 1 at the potential of the former wave gave the 1, 1-dimethylethylamines (3) as well as the hydroxylamines 2. The amines 3 are formed exclusively from 2, probably via the O-protonated form. It is suggested that a phenyl group at the 2-position facilitates the reduction of 2 to 3 by enhancing the adsorption of 2 at the mercury cathode and that a hydroxyl group, while it interferes with the adsorption, assists the reduction by intramolecular hydrogen-bonding to stabilize the O-protonated form of 2.