Direct Green Iodination of Phenol over Solid Acids

Abstract

Examination of several solid acid catalysts of different nature (acid resins, zeolites, mixed oxides, Nb-oxide, and Nb-phosphate) was performed for the direct iodination reaction of phenol by using molecular iodine. The experiments were carried out in mild and green conditions (50 °C at ambient pressure) in methanol in the presence of H2O2 as oxidant agent. Iodine was introduced in reduced amount, stoichiometric for the formation of di-iodinated phenol, to obtain information on the regio-selectivity of the iodination reaction. The catalysts proved to be all efficient for the introduction of iodine into the aromatic substrate, yielding mono-, di-, and tri-iodo derivates. Different selectivity distributions to the iodo-compound formed were observed over the different catalysts. Catalysts could be grouped into distinct families on the basis of their ortho/para orientation. Several solid acid catalysts of different nature were examined for the iodination reaction of phenol by molecular iodine in the presence of H2O2 as oxidant agent. All the catalysts were efficient for the introduction of iodine in the substrate yielding mono-, di-, and tri-iodo derivates. Different selectivity distributions to the ortho- and para-orientation were observed over the different catalysts.