Synlett, Table of Contents Synlett 2022; 33(15): 1527-1531DOI: 10.1055/a-1860-3405 letter Amine Oxidation by Electrochemically Generated Peroxodicarbonate Authors Author Affiliations Ann-Katrin Seitz a Department of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany Tim van Lingen a Department of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany Marco Dyga a Department of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany Philipp J. Kohlpaintner b Department of Chemistry, Johannes Gutenberg Universität Mainz, Duesbergweg 10-14, 55128 Mainz, Germany Siegfried R. Waldvogel b Department of Chemistry, Johannes Gutenberg Universität Mainz, Duesbergweg 10-14, 55128 Mainz, Germany Lukas J. Gooßen∗ a Department of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany Recommend Article Abstract Buy Article(opens in new window) All articles of this category(opens in new window) Abstract The N-oxidation of tertiary amines was achieved by using electrochemically generated peroxodicarbonate solutions as sustainable oxidizers. The presence of EDTA and 2,2,2-trifluoroacetophenone as a mediator was found to be crucial for converting water-insoluble substrates. Various tertiary amines were converted into their corresponding N-oxides in yields of up to 98%. The scope includes economically important surfactants and potential platform oxidizers. Key words Key wordsoxidation - peroxodicarbonate - boron-doped diamond - electrochemistry - amine oxides - organocatalysis Full Text References References and Notes 1a Holmberg K. In Ullmann’s Encyclopedia of Industrial Chemistry 2022; 1b Rice DP. Toxicol. Appl. 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Springer; Berlin: 2012 For their application in the synthesis of peroxodicarbonate, see: 15c Saha MS, Furuta T, Nishiki Y. Electrochem. Solid-State Lett. 2003; 6: D5 15d Saha MS, Furuta T, Nishiki Y. Electrochem. Commun. 2004; 6: 201 15e Chardon CP, Matthée T, Neuber R, Fryda M, Comninellis C. ChemistrySelect 2017; 2: 1037 16 Page PC. B, Marken F, Williamson C, Chan Y, Buckley BR, Bethell D. Adv. Synth. Catal. 2008; 350: 1149 17 Waldvogel S, Zirbes M, Neuber R, Matthée T. DE 102018128228, 2020 18 Gütz C, Stenglein A, Waldvogel SR. Org. Process Res. Dev. 2017; 21: 771 19 Electrosynthesis of Peroxodicarbonate An aqueous electrolyte solution (44 mL) containing K2CO3 (1.136 M), Na2CO3 (0.952 M), and KHCO3 (0.107 M) was added to a 100 mL Schott glass bottle, which was then placed in a cryostat bath (–5 °C). A temperature sensor was placed inside the electrolyte. The solution was circulated through the electrolysis system for 15 min at 50 mL/min until its temperature became constant. The target temperature of the cryostat was then set to –15 °C and the solution was electrolyzed under a circular flow (50 mL/min) using a cooled stainless-steel cathode and a BDD anode (10.8 cm² electrode surface area) at a constant current of 3.84 A (356 mA/cm²) for 1 h (1.5 F relative to CO3 2–). After the electrolysis, the concentration of peroxodicarbonate was determined by iodometric titration of a 4.0 mL aliquot against 0.1 M Na2S2O3. 20a Limnios D, Kokotos CG. J. Org. Chem. 2014; 79: 4270 20b Wang Z.-X, Tu Y, Frohn M, Zhang J.-R, Shi Y. J. Am. Chem. Soc. 1997; 119: 11224 21 Shu L, Shi Y. J. Org. Chem. 2000; 65: 8807 22 Mallat T, Bodmer M, Baiker A. Catal. Lett. 1997; 44: 95 23 N-Methylmorpholine N-Oxide (2a); Typical Procedure The titrated peroxodicarbonate solution (3.4 equiv) was added to N-methylmorpholine (101 mg, 1.00 mmol) and EDTA (73.1 mg, 0.25 mmol, 0.25 equiv) in a 50 mL vial containing a Teflon-coated stirring bar. The mixture was then stirred at RT for 5 h and extracted with EtOAc (20 mL). The aqueous phase was dried by lyophilization and the resulting solid was crushed, suspended in EtOAc, and filtered. The filter cake was washed with EtOAc (4 × 20 mL) and the organic solvent was removed under reduced pressure to give a white solid; yield: 113 mg (0.97 mmol, 97%). 1H NMR (300 MHz, CDCl3): δ = 4.50–4.39 (m, 2 H), 3.81–3.72 (m, 2 H), 3.36 (td, J = 11.4, 3.7 Hz, 2 H), 3.26 (s, 3 H), 3.15–3.06 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 66.0, 61.7, 61.2. HRMS (ESI): m/z [M + H]+ calcd for C5H12NO2: 118.0863; found: 118.0863. The analytical data (NMR) matched those reported in the literature.25a 24 N,N-Dimethyldodecylamine N-Oxide (2b); Typical Procedure for Lipophilic Amines The titrated peroxodicarbonate solution (3.4 equiv) was added to N,N-dimethyldodecylamine (1.00 mmol), EDTA (73.1 mg, 0.25 mmol, 0.25 equiv), and TFAP (35.5 μL, 0.25 mmol, 0.25 equiv) in a 50 mL vial containing a Teflon-coated stirring bar. The mixture was stirred at RT for 5 h and then extracted with EtOAc (5 × 20 mL). The organic solvent was removed under reduced pressure to give a white solid; yield: 226 mg (0.97 mmol, 97%); mp: 130–133 °C (Et2O). 1H NMR (300 MHz, CDCl3): δ = 3.28–3.20 (m, 2 H), 3.18 (s, 6 H), 1.95–1.81 (m, 2 H), 1.41–1.19 (m, 18 H), 0.87 (m, 3 H). 13C NMR (100 MHz, CDCl3): δ = 72.1, 58.9, 32.0, 29.7 (2 C), 29.6, 29.5, 29.4 (2 C), 26.8, 24.1, 22.8, 14.2. HRMS (ESI): m/z [M + H]+ calcd for C14H32NO: 230.2484; found: 230.2487. The analytical data (NMR) matched those reported in the literature.25b 25a Imada Y, Iida H, Ono S, Murahashi S.-I. J. Am. Chem. Soc. 2003; 125: 2868 25b Rauchdi M, Ait Ali M, Roucoux A, Denicourt-Nowicki A. Appl. Catal., A 2018; 550: 266 Supplementary Material Supplementary Material Supporting Information (PDF) (opens in new window)
