Table of Contents
Organic Chemistry International
Volume 2011 (2011), Article ID 835183, 4 pages
Research Article

Tungstosilicic Acid: An Efficient and Ecofriendly Catalyst for the Conversion of Alcohols to Alkyl Iodides

1Department of Chemistry, Rasht Branch, Islamic Azad University, P.O. Box 41325-3516, Rasht, Iran
2Department of Chemistry, Science and Research Amol Branch, Islamic Azad University, P.O. Box 678, Amol, Iran

Received 12 October 2011; Accepted 15 December 2011

Academic Editor: William Ogilvie

Copyright © 2011 Masoud Mokhtary and Faranak Najafizadeh. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Treatment of a range of benzylic, allylic, and secondary aliphatic alcohols with potassium iodides in the presence of H4SiW12O40 affords the corresponding alkyl iodides in good to excellent yield with straightforward purification at room temperature in CH3CN.

1. Introduction

Heteropolyacids (HPAs) and their salts are useful acid and oxidation catalysts for various reactions and there are already many practical applications. There are several advantages from using the HPA catalysts. One of the most interesting aspects may be the fact that they can be used in various kinds of reaction media or fields [13]. There are already several large-scale industrial processes utilizing HPA catalysts [4, 5]. The direct conversion of alcohols to alkyl iodides is a transformation that is widely utilized in organic synthesis [6]. Some alternative reagents reported for this purpose are PPh3/I2/imidazole [7], PPh3/NIS [8], PPh3/DEAD/MeI [9], and P(OPh)3/MeI [10].

A common drawback of all these procedures is generating stoichiometric quantities of triphenyl phosphine oxide or diphenyl methylphosphonate, which can cause difficulties in product purification. Other methods avoid the use of phosphines, the use of HI [15], TMSI [16], N,N-diethylaniline : BF3/I2 [17], TMSCl/NaI [18], P2I4 [19], I2 [20], or of alkali metal iodides in conjunction with Lewis or Bronsted acids such as BF3 OEt2 [21], CeCl3 [22], MsOH [23], Al(HSO4)3 [24], sodium iodide over KSF-clay under microwave irradiation [25], KI/H2SO4 supported on natural kaolinitic clay under microwave irradiation [26] cesium iodide/methanesulfonic acid [27], or MeSCH = I/imidazole [28]. Also, the use of expensive and not easily available reagents such as polymer-supported triphenylphosphine [29] or tris [4-(1H,1H-perfluorooctyloxyphenyl)] phosphine [30] is reported.

In this work, we describe a simple procedure for an efficient conversion of a wide range of allylic, secondary aliphatic, and benzylic alcohols to the corresponding iodides by treatment with the potassium iodide in the presence of H4SiW12O40 in CH3CN at room temperature (Scheme 1).

Scheme 1: Synthetic pathway for the conversion of alcohols to alkyl iodides.

2. Results and Discussion

As shown in Table 1, a variety of benzylic, allylic, and secondary alcohols that were treated with potassium iodides in the presence of H4SiW12O40 affords the corresponding alkyl iodides in good to excellent yield at room temperature in CH3CN. Primary benzylic alcohols (Table 1, entries 1–10) were easily converted to the corresponding benzyl iodides in good to excellent yields. Also, secondary aliphatic and benzylic alcohols (Table 1, entries 11–13) were converted to the corresponding iodides in good yields. No transformation took place when KI without H4SiW12O40 was heated under reflux for 12 h in acetonitrile. Furthermore, under the same reaction conditions, allylic alcohols formed allylic iodides in appropriate yields. It has been observed that the attacking of the iodide ion does not involve allylic rearrangement (Table 1, entries 14,15).

Table 1: Conversion of alcohols into alkyl iodides using H4SiW12O40 at room temperature.

To show the advantage of using heteropolyacid, some of our results compared with those reported in the literature. As shown in Table 2, the iodination of benzyl alcohol with KI in the presence of H4SiW12O40 is simple, efficient, and higher yields of corresponding iodides are important features of this method.

Table 2: Comparison of H4SiW12O40/KI for the conversion of benzyl alcohol into iodide with other reagents.

In conclusion, the present research for the conversion of alcohols into iodides shows that our method may represent a valuable alternative to those reported in the literature. The superiority of this method is the ease of operation, the simplicity of workup, and the environmental advantage that makes the process very useful.

3. Experimental

All chemicals were purchased from Merck. Melting points were recorded on an electro thermal melting point apparatus. The NMR spectra were recorded in CDCl3 with TMS as an internal standard on a Bruker Avance DRX 250 MHz spectrometer. IR spectra were determined on a SP-1100, P-UV-Com instrument. Purity determination of the products was accomplished by TLC on silica gel poly gram SIL G/UV 254 plates. Products were identified by comparing IR and 1H NMR spectra with those reported for authentic samples.

3.1. General Procedure for the Conversion of Alcohols to Iodides

To a mixture of H4SiW12O40 (0.3 g), potassium iodide (2 mmol) in a flask were added acetonitrile (5 mL) and alcohol (1 mmol) at room temperature for 1–3 h. The reaction mixture was monitored by TLC in hexane/ethylacetate (4 : 1) as eluent. After completion of the reaction (TLC), ether (10 mL) was added and washed with aqueous saturated sodium hydrogen carbonate solution, followed by deiodination with sodium hydrogen sulfite. The resultant organic layer was extracted with ether (3 × 10 mL), and the combined extract dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure to afford corresponding iodide in almost pure form. If necessary, products were purified by column chromatography (eluent, hexane-ethyl acetate, 95 : 5). The products were identified by IR and 1H NMR.

3.2. Spectral Data for Compounds

Benzyl Iodide (Table 1, entry 1)
1H NMR (CDCl3): δ = 4.5 (s, 2H, ArCH2I), 7.4 (m, 5H, Ar–H).

4-Chlorobenzyl Iodide (Table 1, entry 2)
1H NMR (CDCl3): δ = 4.34 (s, 2H, ArCH2I), 7.23 (d, 2H, Ar–H), 7.32 (d, 2H, Ar–H).

4-Flourobenzyl Iodide (Table 1, entry 3)
1H NMR (CDCl3): δ = 4.44 (s, 2H, ArCH2I), 7.12 (d, 2H, Ar–H), 7.21 (d, 2H, Ar–H).

2-Chlorobenzyl Iodide (Table 1, entry 4)
1H NMR (CDCl3): δ = 4.2 (s, 2H, ArCH2I), 7.29 (m, 4H, Ar–H).

2-Hydroxybenzyl Iodide (Table 1, entry 5)
1H NMR (CDCl3): δ = 4.22 (s, 2H, ArCH2I), 6.83–7.09 (m, 4H, Ar–H).

4-Isopropylbenzyl Iodide (Table 1, entry 6)
1H NMR (CDCl3): δ = 1.31–1.33 (s, 6H, iPr), 2.99 (m, 1H, –CH), 4.58 (s, 2H, ArCH2I), 7. 27 (d, 2H, Ar–H), 7.40 (d, 2H, Ar–H).

4-Methoxybenzyl Iodide (Table 1, entry 7)
1H NMR (CDCl3): δ = 3.8 (s, 3H, OCH3), 3.9 (s, 2H, ArCH2I), 6.82 (d, 2H), 7.07 (d, 2H).

4-Nitrobenzyl Iodide (Table 1, entry 8)
1H NMR (CDCl3): δ = 4.48 (s, 2H, ArCH2I), 7.50 (d, 2H, Ar–H), 8.12 (d, 2H, Ar–H).

4-Methylbenzyl Iodide (Table 1, entry 9)
1H NMR (CDCl3): δ = 2.41 (s, 3H, CH3), 4.54 (s, 2H, ArCH2I), 7.21 (d, 2H, Ar–H), 7.36 (d, 2H, Ar–H).

1-Iodo-2-phenyl-ethane (Table 1, entry 10)
1H NMR (CDCl3): δ = 2.95 (t, 2H, CH2), 3.35 (t, 2H, CH2I), 7.00–7.12 (m, 5H, Ar–H).

1,1-diphenyl Methyl Iodide (Table 1, entry 11)
1H NMR (CDCl3): δ = 6.17 (s, 1H, ArCHI), 7.20–7.32 (m, 10H, Ar–H).

Iodocyclohexane (Table 1, entry 12)
1H NMR (CDCl3): δ = 0.85–0.99 (m, 4H), 1.4–1.75 (m, 6H), 3.89 (m, 1H, CHI).

5-Iodononane (Table 1, entry 13)
1H NMR (CDCl3): δ = 1.24–1.36 (m, 14H), 1.52–1.56 (m, 4H), 4.14 (m, 1H, CHI).

3-Iodo-1-propene (Table 1, entry 14)
1H NMR (CDCl3) δ = 6.0–6.1 (1H, m), 5.27–5.33 (1H, m), 5.09–5.12 (1H, m), 3.89 (2H, d, J = 7.5 Hz, CH2I).

3-Iodopropenyl Benzene (Table 1, entry 15)
1H NMR (CDCl3): δ = 3.4 (d, 2H, CH2I), 6.6 (m, 1H, =CH), 6.8 (d, 1H, PhCH), 7.20 (d, 5H).


The authors are grateful to Islamic Azad University of Rasht Branch for financial assistance of this work.


  1. T. Okuhara, N. Mizuno, and M. Misono, “Catalytic chemistry of heteropoly compounds,” Advances in Catalysis, vol. 41, no. C, pp. 113–252, 1996. View at Publisher · View at Google Scholar · View at Scopus
  2. I. V. Kozhevnikov, “Catalysis by heteropoly acids and multicomponent polyoxometalates in liquid-phase reactions,” Chemical Reviews, vol. 98, no. 1, pp. 171–198, 1998. View at Google Scholar · View at Scopus
  3. M. Misono, I. Ono, G. Koyano, and A. Aoshima, “Heteropolyacids. Versatile green catalysts usable in a variety of reaction media,” Pure and Applied Chemistry, vol. 72, no. 7, pp. 1305–1311, 2000. View at Google Scholar · View at Scopus
  4. M. Misono and N. Nojiri, “Recent progress in catalytic technology in japan,” Applied Catalysis, vol. 64, pp. 1–30, 1990. View at Google Scholar · View at Scopus
  5. N. Mizuno and M. Misono, “Heterogeneous catalysis,” Chemical Reviews, vol. 98, no. 1, pp. 199–217, 1998. View at Google Scholar · View at Scopus
  6. S. Hartinger, Science of Synthesis, vol. 35, Georg Thieme, New York, NY, USA, 2007.
  7. P. J. Garegg and B. Samuelsson, “Novel reagent system for converting a hydroxy-group into an iodo-group in carbohydrates with inversion of configuration,” Journal of the Chemical Society, Chemical Communications, no. 22, pp. 978–980, 1979. View at Publisher · View at Google Scholar · View at Scopus
  8. S. Hanessian, M. M. Ponpipom, and P. Lavallee, “Procedures for the direct replacement of primary hydroxyl groups in carbohydrates by halogen,” Carbohydrate Research, vol. 24, no. 1, pp. 45–56, 1972. View at Google Scholar · View at Scopus
  9. H. Loibner and E. Zbiral, “Reaktionen mit phosphororganischen Verbindungen. XLI [1]. Neuartige synthetische aspekte des systems triphenylphosphin-azodicarbonsäureester-hydroxyverbindung,” Helvetica Chimica Acta, vol. 59, pp. 2100–2113, 1976. View at Google Scholar
  10. H. N. Rydon, Organic Syntheses, vol. 6, pp. 830–832, 1988.
  11. N. Iranpoor, H. Firouzabadi, A. Jamalian, and F. Kazemi, “Silicaphosphine (Silphos): a filterable reagent for the conversion of alcohols and thiols to alkyl bromides and iodides,” Tetrahedron, vol. 61, no. 23, pp. 5699–5704, 2005. View at Publisher · View at Google Scholar
  12. R. Hosseinzadeh, M. Tajbakhsh, Z. Lasemi, and A. Sharifi, “Chemoselective iodination of alcohols with CeCl3·7H2O/NaI over SiO2 under microwave irradiation,” Bulletin of Korean Chemical Society, vol. 25, pp. 1143–1146, 2004. View at Google Scholar
  13. A. I. Vogel, A Text Book of Practical Organic Chemistry, Longman, 3rd edition, 1975.
  14. Dictionary of Organic Compound, Chapman & Hall, London, UK, 6th edition, 1995.
  15. J. F. Norris, “I am tring to make benzyl chloride by the direct addition of calcium hypo to toluene,” American Chemistry Journal, vol. 38, pp. 627–642, 1907. View at Google Scholar
  16. M. E. Jung and P. L. Ornstein, “A new method for the efficient conversion of alcohols into iodides via treatment with trimethylsilyl iodide,” Tetrahedron Letters, vol. 18, no. 31, pp. 2659–2662, 1977. View at Google Scholar
  17. C. Kishan Reddy and M. Periasamy, “A simple convenient procedure for iodination of alcohols and reductive iodination of carbonyl compounds using N,N-diethylaniline-borane-I,” Tetrahedron Letters, vol. 30, no. 41, pp. 5663–5664, 1989. View at Google Scholar
  18. G. A. Olah, S. C. Narang, B. G. B. Gupta, and R. Malhotra, “Synthetic methods and reactions. 62. Transformations with chlorotrimethylsilane/sodium iodide, a convenient in situ iodotrimethylsilane reagent,” Journal of Organic Chemistry, vol. 44, no. 8, pp. 1247–1251, 1979. View at Google Scholar
  19. M. Lauwers, B. Regnier, M. Van Eenoo, J. N. Denis, and A. Krief, “Diphosphorus tetraiodine (P2I4) a valuable reagent for regioselective synthesis of iodoalkanes from alcohols,” Tetrahedron Letters, vol. 20, pp. 1801–1804, 1979. View at Google Scholar
  20. R. Joseph, P. S. Pallan, A. Sudalai, and T. Ravindranathan, “Direct conversion of alcohols into the corresponding iodides,” Tetrahedron Letters, vol. 36, no. 4, pp. 609–612, 1995. View at Publisher · View at Google Scholar
  21. Y. D. Vankar and C. T. Rao, “Sodium iodide/boron trifluoride etherate: a mild reagent system for the conversion of allylic and benzylic alcohols into corresponding iodides and sulfoxides into sulfides,” Tetrahedron Letters, vol. 26, no. 22, pp. 2717–2720, 1985. View at Google Scholar
  22. M. Di Deo, E. Marcantoni, E. Torregiani et al., “A simple, efficient and general method for the conversion of alcohols into alkyl iodides by a CeCl3·7H2O/NaI system in acetonitrile,” Journal of Organic Chemistry, vol. 65, no. 9, pp. 2830–2833, 2000. View at Publisher · View at Google Scholar
  23. A. Kamal, G. Ramesh, and N. Laxman, “New halogenation reagent system for one-pot conversion of alcohols into iodides and azides,” Synthetic Communications, vol. 31, no. 6, pp. 827–833, 2001. View at Publisher · View at Google Scholar
  24. H. Tajik, F. Shirini, M. A. Zolfigol, and F. Samimi, “Convenient and efficient method for the iodination of benzylic and aliphatic alcohols by using Al(HSO4)3/KI in nonaqueous solution,” Synthetic Communications, vol. 36, no. 1, pp. 91–95, 2006. View at Publisher · View at Google Scholar
  25. G. L. Kad, J. Kaur, P. Bansal, and J. Singh, “Selective Iodination of Benzylic Alcohols with Sodium Iodide over KSF-Clay under Microwave Irradiation,” Journal of Chemical Research S, no. 4, pp. 188–189, 1996. View at Google Scholar
  26. B. P. Bandgar, V. S. Sadavarte, and S. V. Bettigeri, “Selective iodination of benzylic alcohols with KI/H2SO4, supported on natural kaolinitic clay under microwave irradiation,” Monatshefte fur Chemie, vol. 133, pp. 345–348, 2002. View at Google Scholar
  27. K. M. Khan, Zia-Ullah, S. Perveen, S. Hayat, M. Ali, and W. Voelter, “A convenient iodination method for alcohols using cesium iodide/ methanesulfonic acid and its comparison using cesium iodide/ p-toluenesulfonic acid or cesium iodide/aluminium chloride,” Natural Product Research, vol. 22, no. 14, pp. 1264–1269, 2008. View at Publisher · View at Google Scholar · View at PubMed
  28. A. R. Ellwood and M. J. Porter, “Selective conversion of alcohols into alkyl iodides using a thioiminium salt,” Journal of Organic Chemistry, vol. 74, no. 20, pp. 7982–7985, 2009. View at Publisher · View at Google Scholar · View at PubMed
  29. E. Årstad, A. G. M. Barrett, B. T. Hopkins, and J. Köbberling, “ROMPgel-supported triphenylphosphine with potential application in parallel synthesis,” Organic Letters, vol. 4, no. 11, pp. 1975–1977, 2002. View at Publisher · View at Google Scholar
  30. L. Desmaris, N. Percina, L. Cottier, and D. Sinou, “Conversion of alcohols to bromides using a fluorous phosphine,” Tetrahedron Letters, vol. 44, no. 41, pp. 7589–7591, 2003. View at Publisher · View at Google Scholar