Electrochemical synthesis of organophosphorus compounds through nucleophilic aromatic substitution: Mechanistic investigations and synthetic scope

Advantages of the electrochemical approach in the nucleophilic aromatic substitution reaction, such as (a) low cost and ready availability of reagents, (b) atom economy, and (c) high yields (approaching 100 %), are applied to rationalize the (polar or radical) mechanism and to develop new greener synthetic routes for the synthesis of substituted nitroaromatic organophosphorus compounds. The nucleophiles used to study the feasibility and viability of the reaction are the classical tervalent phosphorus nucleophiles: trimethylphosphane, triethylphosphane, triphenylphosphane, diphenylphosphane, trimethyl phosphite, triethyl phosphite, dimethyl phosphonate, diethyl phosphonate, oxo(diphenyl)phosphorane, with two nitroaromatic compounds 1,3,5-trinitrobenzene and 1-chloro-2,4,6-trinitrobenzene in a DMF solution containing 0.1 M tetrabutylammonium tetrafluoroborate. In all cases, in order to establish the feasibility or benefits of the electrochemical approach relative to the chemical approach, blank reactions were also performed. Electrochemical oxidation of σH complexes and zwitterionic complexes obtained by nucleophilic attack of phosphorus nucleophiles was studied by means of cyclic voltammetry and controlled-potential electrolysis. The oxidation mechanism of those intermediates was disclosed, and the synthetic scope of the reaction was explored. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.