04-29-02 18:10
No 303014
      5-iodovanillin (Chloramine T + NaI)
(Rated as: excellent)

Iodination of Phenols using Chloramine T and Sodium Iodide
Tetrahedron Lett., 26 (17), 2044=2046, 1985
It was found, that sodium iodide (1.2 equivalents) and Chloramine T (1.2 equivalents) in DMF, DMSO or
acetonitrile are effective in monoiodination of various phenols. The process accommodated both electron-
withdrawing and electron-donating substituents but failed for phenols bearing a para-oriented methoxy group.
The process can be performed in the presence of sensitive functionalities such as an azide.

Experimental procedure:
To the solution of 100 mg of vanillin and 118 mg of sodium iodide in 3 ml of DMF at 25 C was added 222 mg
of Chloramine T. The mixture was stirred for 1 h. The product was diluted with water, acidified with 5% HCl
and extracted with ethyl acetate. The organic solution was washed successively with 5% sodium thiosulfate
solution and brine and was dried over anhydrous magnesium sulphate. The crude product was crystallised from
ethyl acetate to afford 172 mg (94%) of 5-iodovanillin.

In JCS 1953, 713-715, similar process was used for iodination of phenols (although with worse results) using
acetic acid as a solvent.

Chloramine T = sodium N-chlorotoluene-p-sulphonamide, OTC desinfection product.