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Review
. 2016 May 25;2(5):293-301.
doi: 10.1021/acscentsci.6b00090. Epub 2016 May 3.

Photoredox Catalysis Unlocks Single-Electron Elementary Steps in Transition Metal Catalyzed Cross-Coupling

Mark D Levin  1 , Suhong Kim  1 , F Dean Toste  1
Affiliations
Review

Photoredox Catalysis Unlocks Single-Electron Elementary Steps in Transition Metal Catalyzed Cross-Coupling

Mark D Levin et al. ACS Cent Sci. .

Abstract

Since initial reports, cross-coupling technologies employing photoredox catalysts to access novel reactivity have developed with increasing pace. In this Outlook, prominent examples from the recent literature are organized on the basis of the elementary transformation enabled by photoredox catalysis and are discussed in the context of relevant historical precedent in stoichiometric organometallic chemistry. This treatment allows mechanistic similarities inherent to odd-electron transition metal reactivity to be generalized to a set of lessons for future reaction development.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Generalized mechanism for cross-coupling and representative nucleophiles and electrophiles. Tf = trifluoromethanesulfonyl.
Figure 2
Figure 2
Simplified photoabsorption scheme and commonly employed photoredox catalysts.
Figure 3
Figure 3
Stoichiometric precedent: radical chain oxidative addition to Pt(II) and Au(I).
Figure 4
Figure 4
Generalized scheme for photoredox catalysis of oxidative addition.
Figure 5
Figure 5
Catalytic application: palladium-catalyzed C–H functionalization at room temperature via Pd(IV) intermediates generated by photoredox catalysis.
Figure 6
Figure 6
Catalytic application: gold-catalyzed arylative ring expansion of vinylcyclobutanols via aryl–Au(III) intermediates generated by photoredox catalysis.
Figure 7
Figure 7
Catalytic application: copper-catalyzed C–S bond formation via photoinduced electron transfer. Mechanistic experiments have not distinguished the two potential pathways.
Figure 8
Figure 8
Stoichiometric precedent: oxidatively induced reductive elimination from Fe(IV) and Ni(III). Cp = cyclopentadienyl.
Figure 9
Figure 9
Generalized scheme for photoredox catalysis of reductive elimination.
Figure 10
Figure 10
Catalytic application: nickel-catalyzed etherification with C–O reductive elimination enabled via photoredox catalysis.
Figure 11
Figure 11
Catalytic application: nickel-catalyzed Larock-type indoline synthesis with C–N reductive elimination enabled via photoredox catalysis. IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene.
Figure 12
Figure 12
Generalized scheme for photoredox catalysis of transmetalation.
Figure 13
Figure 13
Catalytic applications: nickel-catalyzed Csp3–Csp2 coupling reactions of alkyltrifluoroborates (racemic) and amino acids (enantioselective). TBAI = tetrabutylammonium iodide, DME = 1,2-dimethoxyethane, Boc = tertbutoxycarbamoyl.
Figure 14
Figure 14
Redox catalysis of migratory insertion. Fc+ = ferrocenium.
Figure 15
Figure 15
Stereoconvergence and diastereoselectivity in nickel-catalyzed radical cross-coupling.
See this image and copyright information in PMC

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