Self-condensation of iodosylbenzene. Formation of a ( p-phenylene) type of bisiodine(III) reagents

Abstract

Reaction of iodosylbenzene (PhIO) with H 2SO 4 was reexamined. When PhIO was treated with excess H 2SO 4, followed by reaction with aromatic substrates such as benzene, toluene, and bromobenzene, aryl(phenyl)( p-phenylene)bisiodonium salts were obtained in good to high yields. In stead of aromatic substrates, treatment of the reagent prepared from PhIO and H 2SO 4 with KI afforded ( p-iodophenyl)(phenyl)iodonium iodide. Similarly, the ( p-phenylene) type of bisiodonium salts were obtained with a fairly strong acid (− H o > 8.0) such as chlorosulfonic acid and trifluoromethanesulfonic acid. These results indicate that the reaction of PhIO with a strong acid gives rise to the formation of ( p-phenylene)bisiodine( III) type of reagent, which leads to ( p-iodophenyl)(phenyl)iodonium salt by the decomposition or to ( p-phenylene)bis(aryliodonium) salts by the reaction with aromatic substrates. The selfcondensation of iodosylbenzene to ( p-phenylene)bisiodine( III) type of reagents is discussed.