Skip to main content
Log in

How to train free radicals for organic synthesis? A modern approach

  • Review Article
  • Published:
Journal of Chemical Sciences Aims and scope Submit manuscript

Abstract

In this review, the journey of free radicals, from being shrewdly untamable until its emergence as a powerful tool in chemistry, has been tracked. A modern perspective on the generation of radicals has been offered through the lens of photoredox, metal mediation, redox-active scaffolds, and EDA complexes. Spotlight has been on the catalysis of radical reactions harboring unique strategies like smart initiation, electron and hole catalysis, and polarity reversal catalysis.

Graphic abstract

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Scheme 1
Figure 1
Figure 2
Scheme 2
Figure 3
Scheme 3
Scheme 4
Scheme 5
Scheme 6
Scheme 7
Scheme 8
Scheme 9
Scheme 10
Scheme 11
Scheme 12
Scheme 13
Scheme 14
Scheme 15
Scheme 16
Scheme 17
Scheme 18

Similar content being viewed by others

References

  1. (a) Romero K J, Galliher M S, Pratt D A and Stephenson C R 2018 Radicals in natural product synthesis Chem. Soc. Rev. 47 785; (b) Plesniak M P, Huang H-M and Procter D J 2017 Radical Cascade Reactions Triggered by Single Electron Transfer Nat. Rev. Chem. 1 0077; (c) Motherwell W B and Crich D 2013 Free Radical Chain Reactions in Organic Synthesis (London: Elsevier); (d) Gibian M and Corley R C 1973 Organic Radical-Radical Reactions. Disproportionation vs. Combination Chem. Rev. 73 441; (e) Curran D P 1988 The design and application of free radical chain reactions in organic synthesis. Part 1 Synthesis 6 417; (f) Gao Y, Zhou D, Lyu J, Sigen A, Xu Q, Newland B, Matyjaszewski K, Tai H and Wang W 2020 Complex Polymer Architectures through Free-Radical Polymerization of Multivinyl Monomers Nat. Rev. Chem. 4 194; (g) Studer A and Curran D P 2016 Catalysis of Radical Reactions: A Radical Chemistry Perspective Angew. Chem. Int. Ed. 55 58

  2. Hedstrand D M, Kruizinga W H and Kellogg R M 1978 Light Induced and Dye Accelerated Reductions of Phenacyl Onium Salts by 1,4-Dihydropyridines Tetrahedron Lett. 19 1255

  3. Pandey G, Ghorai M K and Hajra S 1996 Design of a Photosystem to Harvest Visible-Light into Electrons: Photosensitised One Electron Redox Reactions in Organic Synthesis Pure Appl. Chem. 68 653

    Article  CAS  Google Scholar 

  4. Ischay M A, Anzovino M E, Du J and Yoon T P 2008 Efficient Visible Light Photocatalysis of [2+2] Enone Cycloadditions J. Am. Chem. Soc. 130 12886

    Article  CAS  Google Scholar 

  5. Nicewicz D A and MacMillan D W C 2008 Merging Photoredox Catalysis with Organocatalysis: The Direct Asymmetric Alkylation of Aldehydes Science 322 77

    Article  CAS  Google Scholar 

  6. Lu Z and Yoon T P 2012 Visible Light Photocatalysis of [2+2] Styrene Cycloadditions by Energy Transfer Angew. Chem. - Int. Ed. 51 10329

    Article  CAS  Google Scholar 

  7. Tucker J W, Zhang Y, Jamison T F and Stephenson C R J 2012 Visible-Light Photoredox Catalysis in Flow Angew. Chem. 124 4220

    Google Scholar 

  8. Iqbal J, Bhatia B and Nayyar N K 1994 Transition Metal-Promoted Free-Radical Reactions in Organic Synthesis: The Formation of Carbon-Carbon Bonds Chem. Rev. 94 519

    CAS  Google Scholar 

  9. Nugent W A and RajanBabu T V 1988 Transition-Metal-Centered Radicals in Organic Synthesis. Titanium(III)-Induced Cyclization of Epoxyolefins J. Am. Chem. Soc. 110 8561

  10. Basch C H, Liao J, Xu J, Piane J J and Watson M P 2017 Harnessing Alkyl Amines as Electrophiles for Nickel-Catalyzed Cross Couplings via C-N Bond Activation J. Am. Chem. Soc. 139 5313

    Article  CAS  Google Scholar 

  11. (a) Crisenza G E, Mazzarella D and Melchiorre P 2020 Synthetic Methods Driven by the Photoactivity of Electron Donor–Acceptor Complexes J. Am. Chem. Soc. 142 5461; (b) Lima C G, de M Lima T, Duarte M, Jurberg I D and Paixao M W 2016 Organic synthesis enabled by light-irradiation of EDA complexes: theoretical background and synthetic applications ACS Catal. 6 1389; (c) Yuan Y Q, Majumder S, Yang M H and Guo S R 2020 Recent advances in catalyst-free photochemical reactions via electron-donor-acceptor (EDA) complex process Tetrahedron Lett. 61 151506; (d) Sun J, He Y, An X De, Zhang X, Yu L and Yu S 2018 Visible-Light-Induced Iminyl Radical Formation: Via Electron-Donor-Acceptor Complexes: A Photocatalyst-Free Approach to Phenanthridines and Quinolines Org. Chem. Front. 5 977

  12. (a) Narayanam J M and Stephenson C R 2011 Visible light photoredox catalysis: applications in organic synthesis Chem. Soc. Rev. 40 102; (b) Majek M, Filace F and von Wangelin A J 2014 On the mechanism of photocatalytic reactions with eosin Y Beilstein J. Org. Chem. 10 981; (c) Cismesia M A and Yoon T P 2015 Characterizing chain processes in visible light photoredox catalysis Chem. Sci. 6 5426; (d) Kärkäs M D, Matsuura B S and Stephenson C R 2015 Enchained by visible light-mediated photoredox catalysis Science 349 1285; (e) Silvi M, Schrof R, Noble A and Aggarwal V K 2018 Enantiospecific Three-Component Alkylation of Furan and Indole Chem. - A Eur. J. 24 4279

  13. Ho H E, Pagano A, Rossi-Ashton J A, Donald J R, Epton R G, Churchill J C, James M J, O’Brien P, Taylor R J K and Unsworth W P 2020 Visible-Light-Induced Intramolecular Charge Transfer in the Radical Spirocyclisation of Indole-Tethered Ynones Chem. Sci. 11 1353

    Article  CAS  Google Scholar 

  14. Budén M E, Vaillard V A, Martin S E and Rossi R A 2009 Synthesis of Carbazoles by Intramolecular Arylation of Diarylamide Anions J. Org. Chem. 74 4490

    Article  Google Scholar 

  15. Rossi R A, Alonso R A and Palacios S M 1981 Photostimulated Reactions of Potassium Diphenylarsenide with Haloarenes by the SRNl Mechanism J. Org. Chem. 46 2498

    Article  CAS  Google Scholar 

  16. Camargo Solórzano P, Brigante F, Pierini A B and Jimenez L B 2018 Photoinduced Synthesis of Dibenzofurans: Intramolecular and Intermolecular Comparative Methodologies J. Org. Chem. 83 7867

    Article  Google Scholar 

  17. Woods E F, Berl A J and Kalow J A 2020 Photocontrolled Synthesis of N-Type Conjugated Polymers Angew. Chemie - Int. Ed. 59 6062

    Article  CAS  Google Scholar 

  18. Studer A and Curran D P 2014 The Electron is a Catalyst Nat. Chem. 6 765

    CAS  Google Scholar 

  19. Gu Z Y, Cao J J, Wang S Y and Ji S J 2016 The involvement of the trisulfur radical anion in electron-catalyzed sulfur insertion reactions: facile synthesis of benzothiazine derivatives under transition metal-free conditions Chem. Sci. 7 4067

    Article  CAS  Google Scholar 

  20. Hokamp T, Dewanji A, Lübbesmeyer M, Mück‐Lichtenfeld C, Würthwein EU and Studer A 2017 Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1, 4‐Dioxane Angew. Chem. Int. Ed. 56 13275

    Article  CAS  Google Scholar 

  21. Tang X and Studer A 2018 Alkene 1, 2‐Difunctionalization by Radical Alkenyl Migration Angew. Chem. Int. Ed. 130 822

    Google Scholar 

  22. Okura K, Teranishi T, Yoshida Y and Shirakawa E 2018 Electron‐Catalyzed Cross‐Coupling of Arylboron Compounds with Aryl Iodides Angew. Chem. Int. Ed. 57 7186

    Article  CAS  Google Scholar 

  23. Huang H M, McDouall J J and Procter D J 2019 SmI2-catalysed cyclization cascades by radical relay Nat. Catal. 2 211

    Article  CAS  Google Scholar 

  24. Pabon R A, Bellville D J and Bauld N L 1983 Cation radical Diels-Alder reactions of electron-rich dienophiles J. Am. Chem. Soc. 105 5158

    Article  CAS  Google Scholar 

  25. Pitzer L, Sandfort F, Strieth-Kalthoff F and Glorius F 2017 Intermolecular Radical Addition to Carbonyls Enabled by Visible Light Photoredox Initiated Hole Catalysislena J. Am. Chem. Soc. 139 13652

    Article  CAS  Google Scholar 

  26. Jiang H and Studer A 2018 Amidyl Radicals by Oxidation of α-Amido-Oxy Acids: Transition-Metal-Free Amidofluorination of Unactivated Alkenes Angew. Chem. Int. Ed. 57 10707

    Article  CAS  Google Scholar 

  27. Goulet-Hanssens A, Rietze C, Titov E, Abdullahu L, Grubert L, Saalfrank P and Hecht S 2018 Hole Catalysis as a General Mechanism for Efficient and Wavelength-Independent Z → E Azobenzene Isomerization Chem. 4 1740

  28. Haque M B and Roberts B P 1996 Enantioselective radical-chain hydrosilylation of prochiral alkenes using optically active thiol catalysts Tetrahedron Lett. 37 9123

    CAS  Google Scholar 

  29. Zhou R, Goh Y Y, Liu H, Tao H, Li L and Wu J 2017 Visible-Light-Mediated Metal-Free Hydrosilylation of Alkenes through Selective Hydrogen Atom Transfer for Si−H Activation Angew. Chem. Int. Ed. 56 16621

    Article  CAS  Google Scholar 

  30. Ren S C, Zhang F L, Qi J, Huang Y S, Xu A Q, Yan H Y and Wang Y F 2017 Radical Borylation/Cyclization Cascade of 1,6-Enynes for the Synthesis of Boron-Handled Hetero- and Carbocycles J. Am. Chem. Soc. 139 6050

    Article  CAS  Google Scholar 

  31. Hell S M, Meyer C F, Misale A, Sap J B I, Christensen K E, Willis M C, Trabanco A A and Gouverneur V 2020 Hydrosulfonylation of Alkenes with Sulfonyl Chlorides under Visible Light Activation Angew. Chem. Int. Ed. 59 11620

    Article  CAS  Google Scholar 

  32. Dimakos V, Su H Y, Garrett G E and Taylor M S 2019 Site-Selective and Stereoselective C-H Alkylations of Carbohydrates via Combined Diarylborinic Acid and Photoredox Catalysis J. Am. Chem. Soc. 141 5149

    Article  CAS  Google Scholar 

Download references

Acknowledgements

VG thanks Ramanujan Fellowship (RJN-2018/085) for the financial support. The authors thank IIT Kharagpur for the infrastructure provided.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Venkataraman Ganesh.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Khamrai, A., Ganesh, V. How to train free radicals for organic synthesis? A modern approach. J Chem Sci 133, 5 (2021). https://doi.org/10.1007/s12039-020-01868-0

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1007/s12039-020-01868-0

Navigation