Selective cathodic cleavage of unsymmetrical imidodicarbonates, acylcarbamates and diacylamides

Abstract

A study of the selective cathodic cleavage of one of the alkoxycarbonyl or acyl groups from various imidodicarbonates, acylamides, and diacylamides is reported. The compounds investigated include all 15 possible combinations of the following groups in unsymmetrical N,N-diprotected derivatives, of benzylamine: p-nitrobenzyloxycarbonyl, trichloroethyloxycarbonyl, toluene-p-sulfonyl, benzoyl, benzyloxycarbonyl, and tert-butyloxycarbonyl which can all be electrochemically cleavaged, except the last one. Initially the compounds were examined by cyclic voltammetry in order to measure the potentials associated with the cleavage of each group and afterwards they were electrolysed at constant potential in the presence of a proton donor. The following ranges in negative potential were recorded: 1.03–1.13 V [Z(NO₂)], 1.8–2.14 V (Troc), 1.75–2.41 V (Tos), 1.88–2.52 V (Bz), and 2.83–2.9 V (Z), thus occasionally revealing a drastic effect of the auxiliary group. In the electrolytic experiments competitive attack by base occasionally led to mixtures of monoacylamides. However, all compounds apart from some of the trichloroethyloxycarbonyl derivatives could be selectively cleaved in 89–100% yields when an appropriate proton donor was used. Tentative explanations are given for the behaviour of the compounds studied and some conclusions are drawn.