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.
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.