(Hive Bee)
07-06-03 03:57
No 444801
      Aromatic Iodination: Iodine and NaIO4 or NaIO3
(Rated as: excellent)

Iodination of Both Deactivated and Activated Arenes with Sodium Periodate or Sodium Iodate as the Oxidant
Piotr Lulinski and Lech Skulski, Bulletin of the Chemical Society of Japan Vol. 73, No. 4, pp. 951-956 (2000)
DOI:10.1246/bcsj.73.951  (free pdf article)

Five easy, relatively inexpensive, and environmentally-safe aromatic oxidative iodination procedures are presented; three of them are particularly suitable for deactivated arenes. Nine deactivated arenes, four halobenzenes, benzene, toluene, and N,N-dimethylaniline were reacted upon with the following anhydrous systems: diiodine/NaIO4 or (in four cases) NaIO3/acetic anhydride/glacial acetic acid, acidified with varying amounts of concd (98%) sulfuric acid; the following workups are explained. The aromatic oxidative iodination reactions proceeded mostly at room temperature and within 1—8 h to give fifteen mono- and two diiodinated purified products (sometimes obtained in 2—3 different ways) in 51—95% yields.

We're  all in this world together,
(Hive Bee)
07-07-03 22:53
No 445312
      Tetrahedron Letters 44 (2003) 5099-5101
(Rated as: excellent)


A new, environment friendly protocol for iodination of electron-rich aromatic compounds

Subbarayappa Adimurthy, Gadde Ramachandraiah,* Pushpito K. Ghosh* and Ashutosh V. Bedekar*
Central Salt and Marine Chemicals Research Institute, G.B. Road, Bhavnagar 364 002, India
Received 8 March 2003; revised 18 April 2003; accepted 2 May 2003

Abstract A new environment friendly procedure for effective aromatic iodination is presented. A mixture of potassium iodide
and potassium iodate is used in the presence of an acid for in situ iodination of aromatic compounds.

Aromatic iodo compounds are an important class of compounds in synthetic organic chemistry. They are useful for the preparation of organometallic reagents and some are potential intermediates for the synthesis of pharmaceutical and bioactive materials. They are useful in metal catalyzed coupling reactions which are widely applied in the preparation of complex molecules.

The iodination of organic molecules using elemental iodine is particularly sluggish compared to chlorination and bromination and needs activation for effective electrophilic substitution. The reagents reported for iodination of aromatic substrates include, N-iodosuccinimide (NIS),1 NIS-CF3SO3H,2 NIS-CF3COOH,3 I2-tetrabutylammonium peroxydisulfate,4 I2-nitrogen dioxide,5 I2-diiodine pentoxide,6 I2-silver sulphate,7 I2-mercury salts,8 I2-chromium oxide,9 I2-lead acetate,10 I2-thallium acetate,11 I2-F-TEDA-BF4,12 iodine monochloride,13 BuLi-F3CCH2I,14 NaOCl-NaI,15 bis(symcollidine)- iodine(I) hexafluorophosphate,16 bis(pyridine)-iodonium(I) tetrafluoroborate-CF3SO3H17 and NaIammonium hexanitrocerate.18 Most of these reagents are complicated, costly or use toxic heavy metal catalysts with potential environmental problems due to the generation of hazardous waste. In this note we wish to report our preliminary studies on an efficient, new environmentally benign procedure for aromatic iodination.

The oxidation of an iodide anion results in the formation of an electrophilic iodonium species which is responsible for iodination of the aromatic nucleus. Our method is based on this concept where a mixture of 0.66 mol equiv. of potassium iodide and 0.33 mol equiv. of potassium iodate is treated with one mol equiv. of a mineral acid. This results in the in situ formation of an iodonium cation which can effect aromatic iodination, see Eq. (1).
3ArH + 2I- + IO3- --3H+--> 3 ArI + 3H2O (1)

The test reaction was carried out on anisole in aqueous methanol with potassium iodide and potassium iodate in the presence of hydrochloric acid under ambient conditions. Careful analysis (TLC and GLC) of the reaction products confirmed the formation of 4-iodoanisole with excellent conversion and isolated yield. Having established the feasibility of this conversion, we undertook a systematic study and the results are summarized in Table 1.

Controlled mono iodination of 1,4-dimethoxybenzene was carried out with one equivalent of the iodinating reagent and the desired product, 2-iodo-1,4-dimethoxybenzene was formed in high yield. Iodination of 2-naphthol and 2-methoxynaphthalene resulted in 1-iodo derivatives as the sole products in good, isolable yields. Diiodination of 4-nitrophenol and 4-chlorophenol was achieved in excellent yields while triiodination of phenol was effected with three equivalents of the reagent. Iodination of aniline gave a mixture of para- and ortho-iodoaniline in the ratio of 90:10 in moderate yield, while 4-nitroaniline furnished the 2-iodo-compound in good yield. A previously reported procedure15 for aromatic iodination describes a very low yield of 4-iodo-N,N-dimethylaniline from N,N-dimethylaniline. It is remarkable to observe that the present reagent system was very effective for this particular substrate resulting in an excellent yield of 4-iodo-N,N-dimethylaniline. The iodinated products reported in this study were isolated by column chromatography over silica gel and characterized by standard analytical means and by comparison of their melting points with those reported.

Thus, we have reported our findings on the use of a simple reagent system for an environmentally benign and efficient procedure for the iodination of aromatic compounds.

Table 1. Iodination for aromatic compounds with KI/KIO3/H+
Entry Substrate Iodo %Yielda
1 Anisole, methoxypbenzene 4-Iodo anisole 81
2 Hydroquinone dimethylether, 1,4-dimethoxybenzene 2-Iodo-1,4-dimethoxybenzene 88b
3 2-Methoxy naphtalene 1-Iodo-2-methoxy naphtalene 72
4 2-Naphthol 1-Iodo-2-naphtol 74
5 4-Nitrophenol 2,6-Diiodo-4-nitrophenol 98
6 Phenol 2,4,6-Triiodophenol 99
7 4-Chlorophenol 2,6-Diiodo-4-chlorophenol 99
8 Aniline 4-Iodoaniline 85c
9 Dimethylaniline 4-Iododimethylaniline 83
10 N-Acetylaniline 4-Iodo-N-acetylaniline 80
11 4-Nitroaniline 2-Iodo-4-nitro-aniline 98

a Isolated yield
b by GC analysis
c para:ortho ratio is 90:10 by GC analysis

General procedure for the iodination:
4-Iodoanisole: A solution of anisole (1.00 g; 9.26 mmol), potassium iodide (1.03 g; 6.22 mmol) and potassium iodate (0.66 g; 3.08 mmol) was prepared in methanol (5 mL) and water (30 mL). This mixture was treated at room temperature with dilute hydrochloric acid (9.5 mmol) over 40 to 45 minutes and stirred for an additional 2–3 h, diluted with water (50 mL) and extracted with dichloromethane (25 mL×3). The combined organic extract was washed with dilute sodium thiosulphate (5%), water, brine, dried over anhydrous sodium sulphate and concentrated under reduced pressure to give a thick oil (1.94 g; 90%). Further purification was carried out by crystallization from cold hexane to afford a white crystalline product (1.75 g; 81%), mp 52–54°C (Lit.19 53–54°C), which showed satisfactory analytical and spectroscopic properties.

1. Carreno, M. C.; Ruano, J. L. G.; Sanz, G.; Toledo, M. A.; Urbano, A. Tetrahedron Lett. 1996, 37, 4081.
2. Olah, G. A.; Qi, W.; Sandford, G.; Prakash, G. K. S. J. Org. Chem. 1993, 58, 3194.
3. Castanet, A.-S.; Colobert, F.; Broutin, P.-E. Tetrahedron Lett. 2002, 43, 5047.
4. Yang, S. G.; Kim, Y. H. Tetrahedron 1999, 40, 6051.
5. Noda, Y.; Kashima, M. Tetrahedron Lett. 1997, 38, 6225.
6. Bradzil, L. C.; Cutler, C. J. J. Org. Chem. 1994, 59, 6233.
7. Sy, W.-W. Tetrahedron Lett. 1993, 34, 6223.
8. (a) Gozzelino, G.; Ferrero, F.; Panetti, M. Chem. Ind. (Milan ) 1980, 62, 13; (b) Bachky, A.; Foubelo, F.; Yus, M. Tetrahedron 1994, 50, 5139; (c) Orito, K.; Hatakeyama, T.; Takeo, M.; Suginome, H. Synthesis 1995, 1273.
9. Lulinski, P.; Skulski, L. Bull. Chem. Soc. Jpn. 1997, 70, 1665.
10. Krassowska-Swiebocka, B.; Lulinski, P.; Skulski, L. Synthesis 1995, 926.
11. Cambie, R. C.; Rutledge, P. S.; Smith-Palmer, T.; Woodgate, P. D. J. Chem. Soc., Perkin Trans. 1976, 1161.
12. Zupan, M.; Iskra, J.; Stavber, S. Tetrahedron Lett. 1997, 38, 6305.
13. Lambourne, L. J.; Robertson, P. W. J. Chem. Soc. 1947, 1167; (b) Berlinger, E. J. Am. Chem. Soc. 1956, 78, 3632; (c) Prasada Roa, M. D.; Padmanabha, J. Ind. J. Chem. 1980, 19A, 1179; (d) Hubig, S. M.; Jung, W.; Kochi, J. K. J. Org. Chem. 1994, 59, 6233; With Zeolite catalyst: (e) Sharma, S.; Deshmukh, A. R. A. S.; Singh, A. P. Catal. Lett. 1996, 40, 257.
14. Blackmore, I. J.; Boa, A. N.; Murray, E. J.; Dennis, M.; Woodward, S. Tetrahedron Lett. 1999, 40, 6671.
15. Edgar, K. J.; Falling, S. N. J. Org. Chem. 1990, 55, 5287.
16. Brunel, Y.; Rousseau, G. Tetrahedron Lett. 1995, 45, 8217.
17. Barluenga, J.; Gonzalez, J. M.; Garcia-Martin, M. A.; Campos, P. J.; Asensio, G. J. Org. Chem. 1993, 58, 2058.
18. Sugiyama, T. Bull. Chem. Soc. Jpn. 1981, 54, 2847.
19. Kajigaeshi, S.; Kakinami, T.; Moriwaki, M.; Watanabe, M.; Fujisaki, S.; Okamoto, T. Chem. Lett. 1988, 795.

The candle that burns twice as bright burns half as long
(Chief Bee)
02-13-04 17:06
No 488372
      Aromatic Iodination with I2 and Urea-H2O2 (UHP)
(Rated as: excellent)

Eco-friendly Oxidative Iodination of Various Arenes with a Urea-Hydrogen Peroxide Adduct (UHP) as the Oxidant
Piotr Lulinski, Anna Kryska, Maciej Sosnowski, Lech Skulski
Synthesis 441-445 (2004) (../rhodium/pdf /aromatic.iodination.urea-h2o2-i2.pdf)

Three easy eco-friendly laboratory procedures are presented for the oxidative iodination of various activated and deactivated arenes with molecular iodine, in the presence of UHP (percarbamide), a stable, strongly H-bonded, solid urea-hydrogen peroxide adduct as the oxidant.

The Hive - Clandestine Chemists Without Borders
(Hive Bee)
02-20-04 20:33
No 490025
      Iodination of Activated and Deactivated Arenes
(Rated as: excellent)

Oxidative Iodination of Arenes with Manganese(IV) Oxide or Potassium Permanganate as the Oxidants
Piotr Luliñski and Lech Skulski

Full text, available for free: Bull. Chem. Soc. Jpn., 72, 115-120 (1999) (

Novel and easy laboratory methods (novel Procedures 1-4) are presented for the oxidative mono- and diiodination of both activated and deactivated arenes, which gave the pure iodinated products in 62-89% yields. The reactions were carried out in the anhydrous, strongly acidic medium, I2/activated MnO2/AcOH/Ac2O/conc. H2SO4, firstly at r.t. for 2 h, then at 45-55°C for 2-9 h. The resulting mixtures were poured into excess aq Na2SO3 solution buffered with (NH4)2CO3 to neutralize H2SO4. The following workups are given. Similarly, on carrying out the iodination reactions (at 35°C, for one hour) in the anhydrous, strongly acidic system, I2/KMnO4/AcOH/Ac2O/conc. H2SO4, it was possible to mono- or diiodinate several deactivated arenes in 73-87% yields (improved Procedures 5 and 6).
(Hive Bee)
07-10-04 19:22
No 518568
      Iodination of arenes with KI and H2O2
(Rated as: excellent)

Here's another simple iodination procedure from Synthesis. Aromatic amines are stable to the system, so maybe other amines are too.
It would be nice if this could complement Barium's work on the iodination of 2C-H (Post 383499 (Barium: "A little 2C-I perhaps", Novel Discourse)):

Nonmetal-Catalyzed Iodination of Arenes with Iodide and Hydrogen Peroxide
Jernej Iskra,* Stojan Stavber, Marko Zupan, Synthesis 1869-1873 (2004)

Oxidative iodination of arenes was carried out with one equivalent of KI and two equivalents of 30% hydrogen peroxide in MeOH in the presence of strong acid. Reactions of various substituted anisoles, phenols and anilines, as well as mesitylene and uracil, were selective and effective with very good yields of isolated halogenated aromatic molecules.
(Hive Bee)
09-02-04 00:32
No 528958
      More iodinations     

Tetrabutylammonium peroxydisulfate (made from tetrabutylammonium hydrogen sulfate and sodium peroxydisulfate) and iodine are used to iodinate phenol exclusively in the para- position in 92% yield. 1,4-Dimethoxybenzene is also monoiodinated in 92% yield.

The experimental from the following articles was posted some time ago by foxy2 in Post 199741 (foxy2: "Para-Selective Iodination of Methoxybenzenes", Chemistry Discourse), but the full articles fit nicely into this thread. The second article deals with the preparation of the oxidising agent:

A Practical Iodination of Aromatic Compounds Using Tetrabutylammonium Peroxydisulfate and Iodine
Seung Gak Yang and Yong Hae Kim*
Tetrahedron Letters
, 40 (1999), 6051-6054

A variety of aromatic compounds substituted with an electron donating group such as methoxy, hydroxy, or amino group, were regioselectively iodinated with iodine in the presence of tetrabutylammonium peroxydisulfate under mild conditions in excellent yields.

Novel Direct Tetrahydropyranylation of Alcohols with Tetrahydropyran and Tetra-n-butylammonium peroxydisulfate
Hyun Chul Choi, Kyu Il Cho, and Yong Hae Kim*
, 1995, 207-208

Another interesting method is the use of N-iodosaccharin for the iodination of arenes, and also - perhaps more interestingly - for the hypoiodination of alkenes to give iodohydrins in excellent yields:

N-Iodosaccharin - a New Reagent for Iodination of Alkenes and Activated Aromatics
Darko Dolenc
, 2000, 544-546

A mild and efficient iodination reagent, N-iodosaccharin was prepared. Iodination of activated aromatics and alkenes with the reagent takes place fast and under very mild conditions, without the aid of strong acids or heavy metals. The reagent does not affect oxidizable groups, such as hydroxyl or aldehyde.

(Hive Bee)
10-13-04 12:06
No 535689
      Aromatic iodination with ammonium iodide/Oxone
(Rated as: excellent)

Simple and regioselective oxyiodination of aromatic compounds with ammonium iodide and Oxone®
K.V.V. Krishna Mohan, N. Narender, and S.J. Kulkarni
Tet. Lett., 2004, 45, 8015-8018

Abstract: A simple method for the iodination of aromatic compounds using NH4I as the iodine source and Oxone® as the oxidant is described.

General procedure for the iodination of aromatic compounds: Oxone® (2.2 mmol) was added to a well-stirred solution of NH4I (2.2 mmol) and substrate (2.0 mmol) in methanol (10 mL) and the reaction mixture was allowed to stir at room temperature. The reaction was monitored by thin layer chromatography (TLC). After completion of the reaction, the reaction mixture was filtered and solvent evaporated under reduced pressure. The products were purified by column chromatography over silica gel (finer than 200 mesh) with 5–30% ethyl acetate in hexane as eluent. All the structures of the products were confirmed by NMR and mass spectra.

The tendency is to push it as far as you can
(Hive Addict)
11-11-04 07:47
No 541029
      Novel Easy Preparations of Some Aromatic Iodine     

Note:This has been inserted here from Post 459094 (java: "Re: Novel easy preparations of Iodobenzene.....", Novel Discourse) to compliment this thread

Novel Easy Preparations of Some Aromatic Iodine(I, III, and V) Reagents, Widely Applied in Modern Organic Synthesis *

Lech Skulski

Molecules 8, 45-52,2003

Abstract:... We report our novel (or considerably improved) methods for the synthesis of aromatic iodides, (dichloroiodo)arenes, (diacetoxyiodo)arenes, [bis(trifluoroacetoxy)-iodo]arenes, iodylarenes and diaryliodonium salts, as well as some facile, oxidative anion
metatheses in crude diaryliodonium or tetraalkylammonium halides and, for comparison,potassium halides. All our formerly published papers were discussed and explained in our review ÒOrganic Iodine(I, III, and V) Chemistry: 10 Years of Development at the Medical University of Warsaw, PolandÓ (1990-2000) [1].

It is better to die on your feet than to live on your knees...Emiliano Zapata