Arylazopyrazole linked Schiff bases as organocatalysts for the ipso-hydroxylation of arylboronic acids for the synthesis of phenols

Abstract

A simple metal-free strategy for the synthesis of phenols from aryl and hetero aryl-boronic acids using arylazopyrazole linked o-hydroxyl Schiff base has been illustrated. These sustainable ipso-hydroxylations have very short reaction times, using aqueous H2O2 as the oxidant in aqueous-alcoholic medium. The current protocol has been demonstrated to be effective with a variety of electron-rich and electron-deficient aromatic substrates and provides access to a wide range of phenols. This is the first time that an azoyrazole linked Schiff base has been used to increase the nucleophilicity of H2O2, in oxidative hydroxylation reactions.