Iodocyclization versus diiodination in the reaction of 3-alkynyl-4-methoxycoumarins with iodine: synthesis of 3-iodofuro[2,3-b]chromones

Org Biomol Chem. 2011 Mar 7;9(5):1474-8. doi: 10.1039/c0ob00935k. Epub 2011 Jan 11.

Abstract

The reaction of 3-alkynyl-4-methoxycoumarins with molecular iodine in chlorinated solvents allows access to 3-iodofurochromones in good to excellent yields as the result of a iodocyclization-demethylation process. Competitive diiodination of the coumarin acetylene moiety could be eliminated by simply performing the reactions in refluxing 1,2-dichloroethane, owing to the thermal instability of the resulting (E)-1,2-diiodoethenylcoumarins.