Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

You are viewing this page in draft mode.

Photo-induced iodination of aryl halides under very mild conditions


Aryl iodides are important precursors in synthetic chemistry that form carbon–carbon and carbon–heteroatom bonds. Most methods use transition-metal catalysts, which need to be scrupulously removed before the compounds can be used in the pharmaceutical and electronics industries, where only parts-per-million levels of transition metals are allowed. The aromatic Finkelstein iodination reaction is a powerful method of preparing valuable aryl iodides from cheap but less reactive aryl bromides and chlorides. This protocol describes a transition metal–free method for a photo-induced aromatic Finkelstein iodination reaction that is performed at room temperature (20 °C). With common aromatic bromides and sodium iodide (NaI) as the starting materials, as well as a catalytic amount of I2 as an additive, the corresponding aromatic iodides can be synthesized in yields ranging from 56 to 93% under UV light irradiation in the absence of any metal catalysts. Various functional groups such as nitrile, ester and amino can be tolerated, which will facilitate the further functionalization of the aromatic iodides. The procedure normally requires 38–40 h to complete.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Applications of aryl halides in organic synthesis.
Figure 2: Current approaches to aromatic halogen exchange.
Figure 3: Hypothesis for the mechanism of this photo-induced aromatic Finkelstein reaction.
Figure 4: Examples of aryl iodides that we have prepared at room temperature (rt) with UV light (254 nm) using this protocol.
Figure 5: Reaction setup for Step 1.
Figure 6: System degassing by the freeze–pump–thaw operation.
Figure 7: Photoreaction carried out in the LZC-4V photoreactor.
Figure 8: Reaction setup for gram-scale procedure.
Figure 9: Monitoring the reaction by GC–MS.
Figure 10


  1. 1

    Bunnett, J.F. & Zahler, R. Aromatic nucleophilic substitution reactions. Chem. Rev. 49, 273–412 (1951).

    CAS  Article  Google Scholar 

  2. 2

    Bolm, C., Hildebrand, J.P., Muñiz, K. & Hermanns, N. Catalyzed asymmetric arylation reactions. Angew. Chem. Int. Ed. 40, 3284–3308 (2001).

    CAS  Article  Google Scholar 

  3. 3

    Popov, I., Lindeman, S. & Daugulis, O. Copper-catalyzed arylation of 1H-perfluoroalkanes. J. Am. Chem. Soc. 133, 9286–9289 (2011).

    CAS  Article  Google Scholar 

  4. 4

    Bunevičius, R., Kažanavičius, G., Žalinkevičius, R. & Prange, A.J. Effects of thyroxine as compared with thyroxine plus triiodothyronine in patients with hypothyroidism. N. Engl. J. Med. 340, 424–429 (1999).

    Article  Google Scholar 

  5. 5

    Pimlott, S.L. & Sutherland, A. Molecular tracers for the PET and SPECT imaging of disease. Chem. Soc. Rev. 40, 149–162 (2011).

    CAS  Article  Google Scholar 

  6. 6

    Hallouard, F., Anton, N., Choquet, P., Constantinesco, A. & Vandamme, T. Iodinated blood pool contrast media for preclinical X-ray imaging applications. Biomaterials 31, 6249–6268 (2010).

    CAS  Article  Google Scholar 

  7. 7

    Seevers, R.H. & Counsell, R.E. Radioiodination techniques for small organic molecules. Chem. Rev. 82, 575–590 (1982).

    CAS  Article  Google Scholar 

  8. 8

    Barluenga, J., González, J.M., Martín, M.A.G., Campos, P.J. & Asensio, G. Acid-mediated reaction of bis(pyridine)iodonium(I) tetrafluoroborate with aromatic compounds. A selective and general iodination method. J. Org. Chem. 58, 2058–2060 (1993).

    CAS  Article  Google Scholar 

  9. 9

    Takagi, K., Hayama, N. & Inokawa, S. The in situ-generated nickel(0)-catalyzed reaction of aryl halides with potassium iodide and zinc powder. Bull. Chem. Soc. Jpn. 53, 3691–3695 (1980).

    CAS  Article  Google Scholar 

  10. 10

    Yang, S.H., Li, C.S. & Cheng, C.H. Halide exchange reactions between aryl halides and alkali halides catalyzed by nickel metal. J. Org. Chem. 52, 691–694 (1987).

    CAS  Article  Google Scholar 

  11. 11

    Sheppard, T.D. Metal-catalysed halogen exchange reactions of aryl halides. Org. Biomol. Chem. 7, 1043–1052 (2009).

    CAS  Article  Google Scholar 

  12. 12

    Klapars, A. & Buchwald, S.L. Copper-catalyzed halogen exchange in aryl halides: an aromatic Finkelstein reaction. J. Am. Chem. Soc. 124, 14844–14845 (2002).

    CAS  Article  Google Scholar 

  13. 13

    Casitas, A., Canta, M., Solà, M., Costas, M. & Ribas, X. Nucleophilic aryl fluorination and aryl halide exchange mediated by a CuI/CuIII catalytic cycle. J. Am. Chem. Soc. 133, 19386–19392 (2011).

    CAS  Article  Google Scholar 

  14. 14

    Cant, A.A., Bhalla, R., Pimlott, S.L. & Sutherland, A. Nickel-catalysed aromatic Finkelstein reaction of aryl and heteroaryl bromides. Chem. Commun. 48, 3993–3995 (2012).

    CAS  Article  Google Scholar 

  15. 15

    Chen, M., Ichikawa, S. & Buchwald, S.L. Rapid and efficient copper-catalyzed Finkelstein reaction of (hetero)aromatics under continuous-flow conditions. Angew. Chem. Int. Ed. 54, 263–266 (2015).

    CAS  Article  Google Scholar 

  16. 16

    Li, L. et al. Photo-induced metal-catalyst-free aromatic Finkelstein reaction. J. Am. Chem. Soc. 137, 8328–8331 (2015).

    CAS  Article  Google Scholar 

  17. 17

    M'Halla, F., Pinson, J. & Saveant, J.M. The solvent as H-atom donor in organic electrochemical reactions. Reduction of aromatic halides. J. Am. Chem. Soc. 102, 4120–4127 (1980).

    CAS  Article  Google Scholar 

  18. 18

    Rasmusson, M. et al. Photodissociation of bromobenzene in solution. Chem. Phys. Lett. 367, 759–766 (2003).

    CAS  Article  Google Scholar 

Download references


This work was financially supported by the Canada Research Chair (Tier 1) foundation, the Natural Sciences and Engineering Research Council of Canada, the Fonds de recherchésur la nature et les technologies, the Canada Foundation for Innovation (CFI) and McGill University.

Author information




L.L. and W.L. designed the study; L.L. optimized and performed the experiments and W.L. discovered the initial reaction; L.L., W.L., X.M., C.-J.L. and Z.M. wrote the manuscript; C.-J.L. and Z.M. initiated and supervised the project; all authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Zetian Mi or Chao-Jun Li.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Li, L., Liu, W., Mu, X. et al. Photo-induced iodination of aryl halides under very mild conditions. Nat Protoc 11, 1948–1954 (2016).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing