EPR-electrochemical monitoring of P–C coupling: Towards one-step electrochemical phosphorylation of acridine

• Published in: Electrochimica acta 2022-10, Vol.428, p.140946, Article 140946
• Main Authors: Gryaznova, Tatyana V., Nikanshina, Elizaveta O., Fayzullin, Robert R., Islamov, Daut R., Tarasov, Maxim V., Kholin, Kirill V., Budnikova, Yulia H.
• Format: Article
• Language: English
• Subjects: Acridine; Electrochemistry; EPR; Phosphorylation; Voltammetry
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2022.140946

•EPR spectra of the spin trap bound radical species of (RO)3P oxidation are described.•Co-electrolysis of phosphites and acridine yields aryldialkylphosphonates in one step.•Oxidation potentials of all reaction participants are determined.•The intermediates of the CH phosphorylation were fixed, isolated, and characterized.•CH phosphorylation mechanisms are proposed. A mild, efficient electrochemical approach for the site-selective direct C(sp2)–H phosphonation of acridine with triorganyl phosphites has been developed. Catalyst-, external oxidant- and metal-free joint electrosynthesis leads to selective C9-phosphorylation in good yields. The mechanism of these one-pot oxidative transformations was investigated by voltammetry and electron paramagnetic resonance (EPR) spectroscopy methods. The reaction intermediates, such as dihydroacridine dialkylphosphonates, have been isolated, proven, and investigated by voltammetry, X-ray diffraction, etc. The magnetic resonance parameters of intermediates, the radical cations of triorganyl phosphites captured by a spin trap PBN, acridine, as well as phosphorylated acridine derivatives, have been determined. The EPR and voltammetry data made it possible to reconsider the reaction pathways of 9-phosphono-10-hydroacridanes and 9-diethylphosphono-10-methylacridane and convert them into target derivatives of phosphorylated acridine in electrochemical oxidation reaction.