Autocatalytic aerobic ipso-hydroxylation of arylboronic acid with Hantzsch ester and Hantzsch pyridine

Hantzsch esters are very useful hydrogen and electron donors that have been applied in many reactions. After the reactions, aromatic Hantzsch pyridines are generated as the by-products and their roles are commonly ignored. Herein, we report the use of Hantzsch pyridine as a promoter to activate Hantzsch ester in the generation of the hydrogen peroxy radical, which is useful for the ipso-hydroxylation of arylboronic acids to give phenols. The reaction does not require an external catalyst or light. The conditions are mild and highly compatible with different functional groups.