- Easy, safe, and effective novel methods for preparing either (diacetoxyiodo)-arenes, ArI(OAc)2, or iodylarenes, ArIO2, from the corresponding iodoarenes, ArI, using sodium periodate as the oxidant are presented in this paper. In order to obtain 2- and 4-iodylbenzoic acids, the respective sodium salts of 2- and 4-iodobenzoic acids should be used as the starting substrates, because mixtures containing the corresponding iodosyl derivatives as the main products along with the intended iodyl compounds are produced from the free parent acids.
An improved method is reported for optimized preparations of iodylarenes, ArIO 2 , from iodoarenes, ArI, using NaIO 4 as the oxidant dissolved in boiling 30% (v:v) aq. CH 3 COOH solutions. The former reaction times, reported in Part I, 1 were shortened from 8-16 hours to 3-6 hours, with preserving the same good yields and high purities of the crude final products, ArIO 2 . A considerably improved method of preparing "2-iodosylbenzoic acid" is also reported in this paper. See also our Warning submitted in Experimental.
Deactivated arenes were mono-or diiodinated with strong electrophilic I + reagents, which were prepared from NaIO 4 and either I 2 or KI in concentrated H 2 SO 4 (minimum 95% by weight). In general a small excess of the dark brown iodinating solution was used (1.1/1.5 equivalents, for nitrobenzene two equivalents was required). The iodinations were conducted at 25-30°C with a reaction time of 1-2 hours using either a 'direct' or an 'inverse' method of aromatic iodination to give mono-or diiodinated pure products in 31-91% optimized yields.
Halogenation O 0235Easy, Inexpensive and Effective Oxidative Iodination of Deactivated Arenes in Sulfuric Acid. -The mono-and diiodination of a variety of deactivated arenes is successfully accomplished by use of the I 2 /NaIO 3 /conc. H 2 SO 4 system. The strong electrophilic I + reagent, formed prior the reaction, is applied in 10 to 100% excess, depending on the arene and the grade of iodination. In general, monoiodinations are complete within 1 h whereas the diiodination reaction times are prolonged to 2 h. For two model compounds, benzoic acid and nitrobenzene, I + reagents generated from I 2 and other oxidants are also used with good results for monoiodinations. In addition to the experimental data, all former publications dealing with the direct iodination of deactivated arenes are briefly reviewed. -(KRASZKIEWICZ, L.; SOSNOWSKI, M.; SKULSKI*, L.; Tetrahedron 60 (2004) 41, 9113-9119; Chair Lab. Org. Chem., Fac. Pharm., Med. Acad., PL-02-097 Warszawa, Pol.; Eng.) -Klein 02-043
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