Toward a General Protocol for Catalytic Oxidative Transformations Using Electrochemically Generated Hypervalent Iodine Species
Mohamed Elsherbini and Wesley J. Moran*
*Department of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.,
Email: w.j.moran
hud.ac.uk
M. Elsherbini, W. J. Moran, J. Org. Chem., 2023, 88, 1424-1433.
DOI: 10.1021/acs.joc.2c02309
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Abstract
Using a simple catalytic electrosynthetic protocol, an in situ generated hypervalent iodine species eliminates chemical oxidants and the inevitable chemical waste associated with their mode of action. The developed method has been used for syntheses of dihydrooxazole and dihydro-1,3-oxazine derivatives, and the α-tosyloxylation of ketones.
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proposed mechanism
Catalytic Electrosynthetic Oxidative Cyclization of N-Allyl/Homoallyl Amides
A solution of amide substrate (0.3 mmol, 1 equiv) and tosylic acid (0.75 mmol, 2.5 equiv) in a mixture of HFIP (4 mL) and acetonitrile (1 mL) containing iodobenzene (18.4 mg, 10 μL, 0.09 mmol, 0.3 equiv) was electrolyzed using an ElectraSyn undivided cell (5 mL glass vial) equipped with graphite anode and platinum cathode under constant current of 5 mA with stirring (400 rpm) for 4.82 h (3.0 F). After electrolysis, the electrodes were rinsed with DCM, combined with the reaction mixture, then treated with sat. aq. Na2S2O3 solution (5 mL) and sat. aq. NaHCO3 solution (5 mL), and diluted with DCM (10 mL). The phases were separated, and the aqueous layer was extracted with DCM (2×). The combined organic layers were washed with water (1×) and brine (1×), then dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by flash chromatography using Biotage Isolera Four, applying ethyl acetate/pet. ether 12–100% gradient.
Catalytic Electrosynthetic α-Tosyloxylation of Ketones
A solution of ketone substrate (0.3 mmol, 1 equiv) and tosylic acid (0.75 mmol, 2.5 equiv) in a mixture of HFIP (4 mL) and acetonitrile (1 mL) containing iodobenzene (18.4 mg, 10 μL, 0.09 mmol, 0.3 equiv) was electrolyzed using an ElectraSyn undivided cell (5 mL glass vial) equipped with graphite anode and platinum cathode under constant current of 5 mA with stirring (400 rpm) for 4.82 h (3.0 F). After electrolysis, the electrodes were rinsed with DCM and combined with the reaction mixture, then treated with sat. aq. Na2S2O3 solution (5 mL) and sat. aq. NaHCO3 solution (5 mL), and diluted with DCM (10 mL). The phases were separated, and the aqueous layer was extracted with DCM (2×) The combined organic layers were washed with water (1×) and brine (1×), then dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by flash chromatography using Biotage Isolera Four, applying ethyl acetate/pet. ether 4–40% gradient.
Key Words
2-oxazolines, α-hydroxy ketones, Koser's reagent, electrochemistry
ID: J42-Y2023
