Iodine(I) Reagents in Hydrochloric Acid-Catalyzed Oxidative Iodination of Aromatic Compounds by Hydrogen Peroxide and Iodine
Authors
Department of Physical and Organic Chemistry, Laboratory for Organic and Bioorganic Chemistry, “Jožef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia, Fax: (+386)-1251-9385; phone: (+386)-1477-3631
Department of Physical and Organic Chemistry, Laboratory for Organic and Bioorganic Chemistry, “Jožef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia, Fax: (+386)-1251-9385; phone: (+386)-1477-3631
The Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Jamova 39, 1000 Ljubljana, Slovenia
Department of Physical and Organic Chemistry, Laboratory for Organic and Bioorganic Chemistry, “Jožef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia, Fax: (+386)-1251-9385; phone: (+386)-1477-3631
Hydrochloric acid activates the oxidative iodination of aromatic compounds with the iodine- hydrogen peroxide system through the formation of an iodine(I) compound as the iodinating reagent. Activation with hydrochloric acid is more powerful than that with sulfuric acid. The formation of dichloroiodic(I) acid (HICl2) with various forms of hydrogen peroxide was followed using UV spectroscopy. The HICl2 was used as the iodinating reagent. In the preparative oxidative iodinaton of various aromatic compounds, hydrochloric acid was used in a catalytic amount and the iodine(I) reagent was formed in situ with 0.5 equiv. hydrogen peroxide and 0.5 equiv. molecular iodine. Two types of reactivity were observed in oxidative iodination with iodine(I) species catalyzed by hydrochloric acid: in the iodination of anisole 1a better yields of iodination were observed with a smaller amount of hydrochloric acid, while on the contrary 4-tert-butyltoluene 1b gave better yields of iodination upon increasing the amount of hydrochloric acid. Reactivity was further manipulated by the choice of the solvent (MeCN, trifluoroethanol, hexafluoro-2-propanol).
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