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. 2023 Sep 20;145(37):20169-20175.
doi: 10.1021/jacs.3c06347. Epub 2023 Sep 7.

Ketyl Radical Coupling Enabled by Polycyclic Aromatic Hydrocarbon Electrophotocatalysts

Joseph M Edgecomb  1 , Sara N Alektiar  1 , Nicholas G W Cowper  1 , Jennifer A Sowin  1 , Zachary K Wickens  1
Affiliations

Ketyl Radical Coupling Enabled by Polycyclic Aromatic Hydrocarbon Electrophotocatalysts

Joseph M Edgecomb et al. J Am Chem Soc. .

Abstract

Herein, we report a new class of electrophotocatalysts, polycyclic aromatic hydrocarbons, that promote the reduction of unactivated carbonyl compounds to generate versatile ketyl radical intermediates. This catalytic platform enables previously challenging intermolecular ketyl radical coupling reactions, including those that classic reductants (e.g., SmI2/HMPA) have failed to promote. More broadly, this study outlines an approach to fundamentally expand the array of reactive radical intermediates that can be generated via electrophotocatalysis by obviating the need for rapid mesolytic cleavage following substrate reduction.

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Figures

Figure 1.
Figure 1.
Project overview
Scheme 1.
Scheme 1.
Catalyst discovery and optimizationa aReactions conducted in a divided cell on 0.2 mmol scale in DMF (0.6 M TEAPF6 cathode, 0.6 M TEABr anode) using 1.1 equivalents of styrene with an RVC cathode and zinc anode. Yield determined by GC analysis. All potentials applied are 120 mV more negative than the E1/2 and are reported relative to ferrocene. bAr = 4-n-butoxybenzene. DCA = 9,10-dicyanoanthracene, NpMI = naphthylmonoimide, Ir-1 = Ir(dF-CF3-ppy)2(dtbpy), 4DPAIPN = 2,4,5,6-Tetrakis(diphenylamino)isophthalonitrile, Rub = rubrene, Pery = perylene, BGP = Benzo[ghi]perylene, Anth = anthracene, Pyr = pyrene
Scheme 2.
Scheme 2.
Distinguishing thermal and photochemical SET pathwaysa aReactions were conducted under standard conditions from Scheme 1 in the light and the dark. See SI for further experimental details.
See this image and copyright information in PMC

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