Metal-free iodination of arylaldehydes for total synthesis of aristogins A-F and hernandial

Iodine is one of the most effective sources for iodination of aromatic compounds; however, its electrophilicity is insufficient for direct iodination. The selection of appropriate environmentally friendly and cost-effective oxidants in combination with iodine for the iodination of aromatic rings, along with its application in the synthesis of natural products, holds significant importance. A highly efficient method utilizing I(III) as the initiator has been successfully developed for monoiodination of arylaldehydes. The method demonstrates good compatibility with a wide range of (hetero)aromatic aldehydes, resulting in moderate to excellent yields, without the need for any toxic, volatile or explosive reagents. The synthesis of seven natural products, namely aristogins A-F and hernandial, was achieved through this iodination followed by Ullmann-type coupling.

A simple and efficient synthesis of N-[3-chloro-4-(4-chlorophenoxy)-phenyl]-2-hydroxy-3,5-diiodobenzamide, rafoxanide

A method for the synthesis of rafoxanide 6, a halogenated salicylanilide used as an efficient anthelmintic in sheep and cattle, is presented. Rafoxanide 6 was synthesized in only three steps from readily available 4-chlorophenol with 74% overall yield. The synthesis has two key stages: the first was salicylic acid iodination, adding iodine in the presence of hydrogen peroxide, which allowed obtaining a 95% yield. The second key stage was the reaction of 3,5-diiodosalicylic acid 5 with aminoether 4, where salicylic acid chloride was formed in situ with PCl3 achieving 82% yield. Chemical characterization of both intermediates and final product was achieved through physical and spectroscopic (IR, NMR and MS) techniques.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-023-02846-9.