Recent Advancements on Transition-Metal-Catalyzed, Chelation-Induced ortho-Hydroxylation of Arenes

The phenols are key intermediates as well as desired products in many target oriented syntheses. The conversion of C-H bond to C-O bond is one of the most challenging tasks in organic synthesis. In last few decades, the hydroxylation of aromatic compounds has drawn a considerable attention because of their importance in Pharmaceutical industry, material chemistry, polymers and in agrochemicals. Indeed, transition-metal-catalyzed, coordination-assisted regio- and chemoselectiveortho-hydroxylation of arenes has become very efficient and popular strategy to obtain good yields of phenols with tolerance of a wide range of functional groups. This review is the comprehensive summary of recent advancement on Pd-, Ru-, Rh-, Cu- and Ir-catalyzed, chelation-controlled regioselectiveortho-C-H bond hydroxylation of aromatic compounds in the presence of diverse hydroxylating agents. The review has been classified on the sources of hydroxylating agents used in reaction.