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. 2014 Apr 1;54(4):351-360.
doi: 10.1002/ijch.201300136.

The Development of Visible-Light Photoredox Catalysis in Flow

Zachary J Garlets  1 , John D Nguyen  1 , Corey R J Stephenson  1
Affiliations

The Development of Visible-Light Photoredox Catalysis in Flow

Zachary J Garlets et al. Isr J Chem. .

Abstract

Visible-light photoredox catalysis has recently emerged as a viable alternative for radical reactions otherwise carried out with tin and boron reagents. It has been recognized that by merging photoredox catalysis with flow chemistry, slow reaction times, lower yields, and safety concerns may be obviated. While flow reactors have been successfully applied to reactions carried out with UV light, only recent developments have demonstrated the same potential of flow reactors for the improvement of visible-light-mediated reactions. This review examines the initial and continuing development of visible-light-mediated photoredox flow chemistry by exemplifying the benefits of flow chemistry compared with conventional batch techniques.

Keywords: Photochemistry; Radical reactions; Radicals; Redox chemistry.

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Figures

Figure 1
Figure 1
Proposed mechanism of bromination.
Figure 2
Figure 2
Stephenson’s flow reactor setup.
Figure 3
Figure 3
Gagné’s flow reactor setup (reprinted with permission from Ref. [5e]).
Figure 4
Figure 4
Batch to flow photoredox-mediated deoxygenation.
Figure 5
Figure 5
Photoredox flow setup for the synthesis of aryl sulfides (reprinted with permission from Ref. [20]).
Scheme 1
Scheme 1
Visible-light photoredox reactions in flow.
Scheme 2
Scheme 2
THIQ iminium trapping in batch and flow.
Scheme 3
Scheme 3
Other visible-light-mediated reactions in flow. dF-(CF3)ppy) = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine, dtbbpy = 4,4′-di-tert-butyl-2,2′-dipyridyl.
Scheme 4
Scheme 4
Conjugate addition of glycosyl radicals to acrolein. dmb = 4,4′-dimethyl-2,2′-bipyridine, /Bu-HEH = diisobutyl 2,6-di-methyl-1,4-dihydropyridine-3,5-dicarboxylate.
Scheme 5
Scheme 5
Zeitler’s comparative study of the synergistic effect of organocatalytic α-alkylations.
Scheme 6
Scheme 6
Reductive deiodination in flow.
Scheme 7
Scheme 7
Photoredox flow chemistry for deoxygenation.
Scheme 8
Scheme 8
Visible-light photocyclization to form [5]-helicene.
Scheme 9
Scheme 9
Photoredox coupling of thiophenols and aryl amines.
Scheme 10
Scheme 10
Flow photoredox catalyzed by rose bengal.
Scheme 11
Scheme 11
Multicomponent reaction in photoredox flow.
See this image and copyright information in PMC

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