Benzyltrimethylammonium Dichloroiodate1

[114971-52-7]  · C10H16Cl2IN  · Benzyltrimethylammonium Dichloroiodate  · (MW 348.05)

(iodinating agent for aromatic compounds;1 chloroiodo addition to unsaturated bonds;1 a-chlorination of acetyl derivatives1)

Physical Data: mp 125-126 °C.

Solubility: sol CH2Cl2, MeCN, MeNO3, DMSO, DMF; slightly sol MeOH, EtOH, AcOEt; insol C6H14, Et2O, CCl4, CHCl3, C6H6, AcOH.

Form Supplied in: yellow needles.

Analysis of Reagent Purity: 1H NMR (CD3CN) d 3.11 (s, 9H, 3 CH3), 4.48 (s, 2H, CH2), 7.50 (s, 5H, C6H5).

Preparative Methods: to a solution of ICl (16.2 g, 0.1 mol) in CH2Cl2 (200 mL) at room temperature is added dropwise over 30 min a solution of benzyltrimethylammonium chloride (18.6 g, 0.1 mol) in water (100 mL); yield 30 g (86%).2

Purification: recrystallize from CH2Cl2-Et2O (3:1).

Handling, Storage, and Precautions: stable solid; gradually decomposes in water. This reagent should be handled in a fume hood.

Electrophilic Iodination of Aromatic Compounds.

This solid reagent (1) can be used stoichiometrically in place of viscous Iodine Monochloride to iodinate aromatic compounds (eq 1). The iodinating ability of (1) is considerably higher than that of molecular Iodine.

The reaction of phenols with (1) in CH2Cl2-MeOH in the presence of powdered Calcium Carbonate or NaHCO3 for several hours at room temperature gives iodophenols in 63-96% yield. Because the presence of MeOH markedly facilitates the reaction, it is assumed that the active species is methyl hypoiodite (MeOI) produced from (1) and MeOH. NaHCO3 is used for the iodination of phenols bearing electron-attracting substituents, and CaCO3 is used for the iodination of phenols bearing electron-releasing groups.2

The reaction of aromatic amines with (1) in CH2Cl2-MeOH in the presence of CaCO3 powder at room temperature gives iodo-substituted aromatic amines (73-96% yield). In these cases it is necessary to add CaCO3 powder to remove the HCl generated.3 The reaction of aromatic ethers with (1) in AcOH in the presence of Zinc Chloride at room temperature gives iodo-substituted aromatic ethers (87-98% yield). The reagent is insoluble in AcOH at room temperature, but the addition of ZnCl2 increases its solubility, allowing the iodination of aromatic ethers to proceed smothly under mild conditions. An equimolar amount of ZnCl2 with respect to (1) is required. Thus 2-methylanisole gives 97% yield of 4-iodo-2-methylanisole via the above iodination.4

The reaction of acetanilides with (1) in AcOH-ZnCl2 at room temperature or at 70 °C gives iodo-substituted acetanilides (60-97% yield). Thus treating acetanilide with (1) in AcOH-ZnCl2 at room temperature for 2 h gives a 77% yield of 4-iodoacetanilide.5

The reaction of simple arenes with (1) in AcOH-ZnCl2 at room temperature or at 70 °C gives iodo-substituted products in 40-99% yield. Thus treating 1,4-dimethylbenzene with 1 equiv of (1) at room temperature for 16 h gives a 75% yield of 2-iodo-1,4-dimethylbenzene, and with 2 equiv of (1) at 70 °C for 72 h gives a 67% yield of 2,5-diiodo-1,4-dimethylbenzene.6 The reaction of ethyl 4-aminobenzoate with 1 equiv of (1) in CH2Cl2-MeOH in the presence of CaCO3 at room temperature for 48 h gives ethyl 4-amino-3-iodobenzoate in 97% yield.7 The reaction of thiophenes with (1) in AcOH-ZnCl2 under mild conditions gives iodo-substituted thiophenes (39-98% yield). For example, the reaction of 3-methylthiophene with 2 equiv of (1) in AcOH in the presence of ZnCl2 at room temperature for 4 h gives a 92% yield of 2,5-diiodo-3-methylthiophene.8

Chloroiodo Addition to Unsaturated Bonds.

The reaction of alkenes with (1) in CH2Cl2 at room temperature gives the chloroiodo adducts in an anti stereospecific and regioselective manner (eq 2); in methanol these adducts are obtained along with methanol-incorporated products.9

a-Chlorination of Acetyl Derivatives.

The reaction of aromatic acetyl derivatives with 2 equiv of (1) in an appropriate solvent give a-chloro acetyl derivatives (eq 3). Thus the reaction of acetophenone with (1) in refluxing ClCH2CH2Cl-MeOH for 3 h gives a 97% yield of a-chloroacetophenone,10 and the reaction of 2-acetylpyrrole with (1) in THF at room temperature for 12 h gives 2-chloroacetylpyrrole in 85% yield.11


1. Kajigaeshi, S.; Kakinami, T. Yuki Gosei Kagaku Kyoukai Shi 1993, 51, 366 (CA 1993, 119, 94 683a).
2. Kajigaeshi, S.; Kakinami, T.; Yamasaki, H.; Fujisaki, S.; Kondo, M.; Okamoto, T. CL 1987, 2109.
3. Kajigaeshi, S.; Kakinami, T.; Yamasaki, H.; Fujisaki, S.; Okamoto, T. BCJ 1988, 61, 600.
4. Kajigaeshi, S.; Kakinami, T.; Moriwaki, M.; Watanabe, M.; Fujisaki, S.; Okamoto, T. CL 1988, 795.
5. Kajigaeshi, S.; Kakinami, T.; Watanabe, F.; Okamoto, T. BCJ 1989, 62, 1349.
6. Kajigaeshi, S.; Kakinami, T.; Moriwaki, M.; Tanaka, T.; Fujisaki, S.; Okamoto, T. BCJ 1989, 62, 439.
7. Hirschfeld, J.; Buschauer, A.; Elz, S.; Schunack, W.; Ruat, M.; Traiffort, E.; Schwartz, J.-C. JMC 1992, 35, 2231.
8. Okamoto, T.; Kakinami, T.; Fujimoto, H.; Kajigaeshi, S. BCJ 1991, 64, 2566.
9. Kajigaeshi, S.; Moriwaki, M.; Fujisaki, S.; Kakinami, T.; Okamoto, T. BCJ 1990, 63, 3033.
10. Kajigaeshi, S.; Kakinami, T.; Moriwaki, M.; Fujisaki, S.; Maeno, K.; Okamoto, T. S 1988, 545.
11. Croce, P. D.; Ferraccioli, R.; Ritieni, A. S 1990, 212.

Shoji Kajigaeshi

Yamaguchi University, Ube, Japan

Takaaki Kakinami

Ube Technical College, Ube, Japan



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