Electrochemical Reactivity of N-Alkoxyphthalimides, Towards O Radicals Electrogeneration and Use in Electrosynthesis

Abstract

N-alkoxyphthalimides (NAPIs) are compounds known for the capability of oxygen-centered radical generation in the presence of tin reagents and radical initiators,[1] which have led to some inovative synthesis strategies.[2,3] Their reported electrochemical behavior is quite different: carbonylic compounds are obtained through cathodic reduction benzylic NAPIs.[4] Encouraged by an exciting "oxidation under cathodic conditions," we focus our studies on contrasting experimental with simulated cyclic voltammetry data using specialized software aiming to prove a plausible mechanism. The synthetic application to accessing carbonylic compounds through NAPIs electrochemical reduction has been assessed, evaluating different solvents, supporting electrolytes and current densities, and the tolerance of other reactive moieties to the reaction conditions.[1] Kim, S.; Lee, T. A.; Song, Y. Facile Generation of Alkoxy Radicals from N-Alkoxyphthalimides. Synlett 1998, No. 5, 471–472.[2] Cortezano-Arellano, O.; Quintero, L.; Sartillo-Piscil, F. Total Synthesis of Cephalosporolide E via a Tandem Radical/Polar Crossover Reaction. The Use of the Radical Cations under Nonoxidative Conditions in Total Synthesis. J. Org. Chem. 2015, 80 (5), 2601–2608.[3] Zhu, H.; Leung, J. C. T.; Sammis, G. M. Strategies to Control Alkoxy Radical-Initiated Relay Cyclizations for the Synthesis of Oxygenated Tetrahydrofuran Motifs. J. Org. Chem. 2015, 80 (2), 965–979.[4] Syroeshkin, M. A.; Krylov, I. B.; Hughes, A. M.; Alabugin, I. V.; Nasybullina, D. V.; Sharipov, M. Y.; Gultyai, V. P.; Terent’ev, A. O. Electrochemical Behavior of N-Oxyphthalimides: Cascades Initiating Self-Sustaining Catalytic Reductive N―O Bond Cleavage. J. Phys. Org. Chem. 2017, 30 (9), 1–15. Figure 1