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Visible-Light Mediated Oxidative Fragmentation of Ethers and Acetals by Means of Fe(III) Catalysis

Rickard Lindroth, Alica Ondrejková and Carl-Johan Wallentin*

*Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden, Email: carl.wallentinchem.gu.se

R. Lindroth, A. Ondrejková, C.-J. Wallentin, Org. Lett., 2022, 24, 1662-1667.

DOI: 10.1021/acs.orglett.2c00231


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Abstract

Iron(III) acetylacetonate catalyzes an oxidative ring opening of cyclic ethers and acetals under visible light irradiation with unparalleled efficiency. This photocatalytic radical chemistry approach enables the conversion of relatively inert cyclic ethers into useful synthetic intermediates and illustrates that simple Fe(III) complexes can initiate redox processes from 4LMCT excited states.


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proposed mechanism



Experimental procedure for photoreaction

All reactions were run in duplicate unless otherwise stated. Dichloroethane (DCE, anhydrous) and BrCCl3 were deoxygenated by sparging with argon for 20 min. Cyclic ether or acetal (0.2 mmol), Fe(acac)3 (1 mol%) and a stir bar was added to a Biotage MW vial (10 ml) and capped. Reaction atmosphere was exchanged to argon by "sparging" head space for 10 min. Then BrCCl3 (3 eq. 60 µL) followed by DCE (0.1 M, 2 ml) was added. The capped end of the vial was wrapped with parafilm and then placed in a photoreactor and irradiated with 455 nm light for 18 h at 27°C (with fan). The two duplicated reactions were combined and adsorbed onto Celite and purified on silica. Isolated yields were thereby obtained as an average.


Key Words

Bromides, Ketones, Photochemistry


ID: J54-Y2022